MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATIN ...

Joumal of the American Mosquito Control Association, 16(4):295-312,2OOOThe copyright of the publication does not extend to this article.

MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATINAMERICA-A TENTH SYMPOSIUM

GARY G. CLARK,I HUMBERTO QUIROZ MARTiNEZ'AND YADIRA N. RANGEL3(ORGANIZERS)

ABSTRACT. The 10th annual Latin American symposium presented by the American Mosquito ControlAssociation (AMCA) was held as part of the 66th Annual Meeting in Atlantic City, NJ, in March 2000. Theprincipal objective, as for the previous 9 symposia, was to promote participation in the AMCA by vector controlspecialists, public health workers, and academicians from Latin America. This publication includes summariesof 57 presentations that were given orally in Spanish or presented as posters by participants from 9 countries inLatin America. Topics addressed in the symposium included results from chemical and biological control pro-grams and studies; studies of insecticide resistance; and molecular, ecological, and behavioral studies of vectorsof dengue (Aedes aegypti), malaria (Anopheles albimanus and Anopheles aqunsalis), leishmaniasis (Lutzomyia),and Chagas' disease (Triatona). Related topics included biology and control of scorpions and, Chintnomusplumosus.

KEY WORDS Mosquitoes, mosquito control, Aedes, Anopheles, Culex, Lutzomyia, Triatoma, scorpions, Cftl-ronomus resistance

INTRODUCTION

The American Mosquito Control Association(AMCA) is dedicated to the study and control ofmosquitoes and other vectors and promotes coop-eration and interaction among professionals andstudents in this field both in the USA and interna-tionally. To promote greater involvement of onesegment of the international membership, a Spanishlanguage symposium was held at the AMCA An-nual Meeting in 1991 and symposia have been heldat subsequent meetings. In addition to providing aforum for scientists whose primary language isSpanish, the session promoted interaction and espritde corps within this group, interaction with controlindustry representatives, and interaction with pro-fessional colleagues in the USA who are involvedin mosquito vector control, training, and researchat the university level, and with state and federalgovernment officials.

This publication includes summaries of 57 pre-sentations that were given in Spanish by partici-pants from 9 countries in Latin America. Topicsaddressed in the symposium included results fromchemical and biological control progrnms and stud-ies, studies of insecticide resistance, and molecular,ecological, and behavioral studies of scorpions andChironomus, vectors of dengue (Aedes aegypti(L.)), malaria (Anopheles albimnnus Wiedemannand Anopheles aquasalis Curry), leishmaniasis(Lutzomyia), and Chagas' disease (Triatoma). Sum-maries of 8 previous symposia have been published

I Dengue Branch, Centers for Disease Control and Pre-vention, 1324 Calle Caffada, San Juan, PR 00920-3860.

'�Laboratorio de Entomologia, Facultad Ciencias Biol-6gicas, Universidad Aut6noma de Nuevo Le6n, San Ni-col6s de los Garza, Nuevo Le6n, M6xico.

3 Laboratorio de Biologia de Vectores, Instituto deZoologia Tiopical, Universidad Central de Venezuela, Ca-racas, Venezuela.

(Clark and Suarez 1991,1992,1993; Clark 1995,1996; Clark and Rangel 1997,1998, 1999).

Financial support for this session was providedby the following sponsors and individuals: ClarkeMosquito Control Products (Lyell Clarke), CurtisDyna-fog (Mike Delara), H.D. Hudson (Manuel L.Lluberas), Zeneca (Eduardo Moreira), ZoeconlWellmark (Greg Braithwaite), Rockefeller Foun-dation, and the Pan American Health Organization.Funds from these sponsors provided Annual Meet-ing registration and partially defrayed travel ex-penses of symposium participants. Enthusiasm andinterest for this symposium was high and it willcontinue to be a part of future meetings.

SUMMARIES

Integrating vector control with the WorldHealth Organization's healthy cities andprimary environrnental care strategies

Steven K. Ault

Pan American Health Organilation (PAHO|World Health Organization (WHO| Brasilia,

Brazil

ln developing countries, vector control programsneed to leverage their scarce resources with envi-ronmental and public health programs at the na-tional, state, and municipal levels in order to opti-mize surveillance, prevention, and control ofvectors. Dozens of cities worldwide are participat-ing in the World Health Organization's (WHO's)Healthy Cities program, which addresses local en-vironmental and public health needs in a commu-nity-based manner. As well, WHO's Primary En-vironmental Care strategy places emphasis onmanaging local environmental health problems inboth rural and urban areas. These programs are de-scribed with examples, and examined as to howthey have been and can be linked to vector control

296 JounNer- oF THE AMERICAN Moseurro CoNrnol AssoctanoN Vor-. 16. No.4

programs. Special emphasis is given to integratingcontrol of dengue and malaria vectors in the localHealthy Cities program (e.g., potable water, sani-tation, drainage, and solid waste management in-terventions) and a Primary Environmental Carestrategy (e.g., use of local environmental health in-dicators and community participation in prevention,surveillance, control, and evaluation).

The dengue situation in the Americas withspecial reference to the Brazilian Control

Program

Christian Frederickson

Communicable Disease Control Program, PanAmerican Health Organization (PAHO), World

Health Organization (WHO), Brasilia, Brazil

Dengue and its severe form, dengue hemorrhagicfever, is the most important and rapidly spreadingarbovirus infection in the Americas. The number ofcases reported in countries from Mexico to Brazilhave increased dramatically, as have the number ofreported deaths. The response of affected or threat-ened countries has ranged from limited action tothe reinitiation of an Aedes aegyptl eradication pro-gram. The dengue epidemiologic situation in LatinAmerica for the past 5 years is reviewed. More thanTOVo of the cases in 1998 have been reported fromBrazil. To combat this, Brazil launched an aggres-sive and massive eradication campaign. Details ofthe control efforts are examined and the results arecritically evaluated.

Spatial and temporal analysis of dengue casesin the metropolitan area of Monterrey, Nuevo

Le6n, M6xico, during 1998

Sadl Lozano-Fuentes, Roberto Mercado-Hern6ndez and Ildefonso Fern6ndez-Salas

Universidad Aut6noma de Nuevo Le6n (UANL|Facultad de Ciencias Biol6gicas, Laboratorio deEntomologia Mddica, San Nicolds de los Garza,

Nuevo Le6n, Mdxico

The number of dengue cases and their severityhave increased in recent years in Nuevo Le6n State.Development of systems to evaluate and supportvector control actions are needed. Epidemiologicinformation on these cases was provided by theNuevo Le6n State Health Department and layeredpolygons of the geostatistic basic area were takenfrom the maps digitized by the National Institute ofStatistics, Geography and Informatics. The caseswere divided by 15-day time intervals from July toDecember 1998, and a map was created for eachperiod. The distribution map of cases for 1998showed that dengue vectors were distributed in alarge part of the metropolitan area. Of the 968 geo-statistic basic areas. 314 contained at least I case.

A continuous area was identified where 60% of thedengue cases occurred. Ten principal componentswere obtained; component 1 presents a variabilityof 34.68Vo. Ninety-one percent of variability wasobtained in 6 components.

Spatial analysis of dengue cases in Guadalupe,Nuevo Lerin, M6xico, 1995-96

Roberto Mercado, Ildefonso Ferndndez and SarilLozano

Universidad Aut6noma de Nuevo Le6n, Facultadde Ciencias Biol6gicas, San Nicokis de los Garza,

Nuevo Le6n, M€xico

The spatial and temporal distribution of denguefever cases in Guadalupe, Nuevo Le6n, M6xico, wasanalyzed using a geographic information system.Data were obtained from the state health departmentand mapped for the municipality of Guadalupe, us-ing CARTALINXo and IDRISI@ programs. Con-firmed cases (689) of dengue occurred most fre-quently in October (42.3Vo) and November (43.9Vo)and more cases were reported in women (59.l%o)than men. The age group from 2l to 3O years hadthe most (25.3Vo) cases. The dengue cases wereranked at 5 levels: 1-2 cases, 3-5, 6-7,8-9, and)9 cases, and then mapped. In 1995, the spatialdistribution of 545 dengue fever cases was concen-trated in the south, but in October they were con-centrated in the south-central sector and in Novem-ber they were concentrated in the west-central area.In 1996, most (145) were distributed in the east-central area. Factors such as human population den-sity and availability ofbasic sanitary services influ-enced dengue incidence.

Effect of an educational campaign for Aedesaegypti control in Colima, Mexico

F Espinosa G6mez, C. M. Hernr4ndez Suarez,X. Montoy Guzmi4n and I. Ferndndez Salas

Faculty of Medicine, University of Colima,Mexico; and Department of Medical Entomology,

Faculty of Biological Sciences, UniversidadAuton6ma de Nuevo Le6n (UANL), San Nicolds

de los Garza, Nuevo Le6n, Mdxico

As a part of a community participation programfor Aedes aegypti control in Colima, M6xico, 187houses were sampled for presence of larval positivecontainers following the recommendations of thePan American Health Organization. The Breteau in-dex and positive container/house (C+/H) were de-termined for each dwelling at the beginning of thestudy and after 6 months. A total of 374 observa-tional units were computed. Simultaneously, a pre-mise condition index (PC! was assessed according

'to Tun-Lin. Spearman's correlation between C*AIand PCI showed a weak, but significantly positive

DecsMenn 2000 Svuposrurvr oN Moseuno CoNtnol tN L,qrtn AIragnIcl 297

correlation (r : 0.2, t : 4.02, P : 0.0005); mean-while a logistic regression betwen PCI and posi-tive-negative houses revealed a significant corre-lation (1'� = 3.4, P < 0.04, OR : 1.61, CI 1.0-2.61). These results support the original hypothesisstated by Tun-Lin: that it is possible to estimateaccurately the risk for house infestation with Ae.aegypti from a simple inspection. This strategycould reduce costs and time when Ae. aegypti sur-veillance campaigns are planned.

Evaluation of a natural fertilizer infusion as anattractant for Aedes aegypti oviposition

Marfa de Lourdes da Graga Macoris, MarfaTeresa Macoris Andrighetti, Luiz Takaku, Vanessa

Camargo Garbeloto and Vanusa Cristina BusatoCirino

Superintendencia de Control de Endemias,S e rv ic io Re g ional Marilia, Supe rintendencia de

Control de Endemias, Sucen, Serv. Reg. deMarilia, Brazil

Flower vases are one of the most importantbreeding sites of Aedes aegypti in Brazil. A naturalfertilizer for plants (diluted cow excrement) wasevaluated as an attractant for Ae. aegypti oviposi-tion in the laboratory and under field conditions. Inthe laboratory, a cage with 200 female and 20Omale Ae. aegypi was used. Three glasses filled withwater and with filter paper around the edge wereused as oviposition sites. The glasses were filledwith tap water, the pure fertilizer (l0o7o), or thediluted fertilizer (lOVo). A strong preference foroviposition in the pure fertTlizer (57Vo of the eggs)was observed, followed by oviposition in the glasswith diluted fertilizer (33.8Vo), and 9.2Vo in tap wa-ter. In the field, the product was evaluated withpaired ovitraps (with tap water and the lOVo fertll-izer). The paired ovitraps were placed in 65 housesof an urban area of Marilia. Sao Paulo State. Brazil.They were serviced weekly for I year (March1998-March 1999). No significant differences werefound between positivity in ovitraps with the fer-tilizer and with plain water but a significantly high-er number of eggs were laid in the ovitraps withfertilizer (t : 3.1617. P : 0.95).

Gonotrophic cycle, survival, and pregravid rateof Aedes aegypti with mark-release-recapture

method in Monterrey, northeastern Mexico

M. L. Rodriguez-Tovar, M. H. Badii, A. Flores-Su6rez and I. Fernandez-Salas

Department of Invertebrate Zoology andlaboratory of Medical Entomology, School ofBiological Sciences, UANL, San Nicoltis de los

Garza, Nuevo Le6n, Mdxico

Feeding frequency and survivorship along withmultiple partial blood meals represent important

vectorial capacity variables for the dengue vector,Aedes aegypf1. As a part of a project to study thebionomics of Ae. aegyptr, this field study aimed todetermine the length of the gonotrophic cycle andthe pregravid rate, or the need of females to havea 2nd blood meal in order to stimulate oogenesis.The study site was located in Guadalupe City, partof the metropolitan area of Monterrey, in north-eastern M6xico. This region has reported seriousdengue outbreaks since 1995. A group of 1,100field-caught females reared in the laboratory werereleased in the field. They were marked with fluo-rescent powder 24-48lr after emergence. Three re-leases were conducted in order to obtain consisten-cy of results. A recapture period of 9 dayspostrelease using human bait collections was con-ducted. Recaptured females that had been markedwere taken to the laboratory and classified accord-ing to trophic stage and ovaries were dissected foroogenesis progression. Results showed that mostAe. aegypti females were recaptured at 4.5 days.Trophic stages of recaptured Ae. aegypti femalesshowed 66Vo (75lIl3) were unfed,24Vo (27lll3)

had fed, and 8Vo (11/ll3) were pregravid. Dailysurvivorship calculated by Guilles' regressionmethod was 0.86, 0.83, and 0.78, for each of the 3repetitions. Discussion on the importance of fieldstudies to redefine known variables of the vectorialcapacity for Ae. aegypti is also included.

Evaluation of the perifocal application ofCypermethrin 40 WP for the control of Aedes

aegypti in Brazil

I. Braga, R. Pimenta Faria, C. Frederickson,A. K. Ribeiro Galardo and S. da Silva Soares

Fund. Nac. de Saude. Brasilia, Brazil

A comparative study to determine the effective-ness of Cypermethrin 40 WP as a perifocal treat-ment for the control of Aedes aegypti was con-ducted in Novo Iguagri, Rio de Janeiro, andManaus, Amazonas. Three application rates (125mg active ingredient [Al]/m'�; 25Q mg AVm2, and500 mg AUm) were used to treat the external sur-faces of large water storage containers such as 5O-gal plastic or painted steel drums and asbestos wa-ter tanks. Bioassay results indicated that mortalitydecreased from 95Vo on day 1 after the treatmentto less than 2OVo in the asbestos water tanks (treatedwith 125 mg AVm'� and 250 mg AVm'�). At thehighest application rate, mortality decreased from98 b 47qa. With the plastic tanks the mortality de-creased by approximately 5OVo. The results indicatethat Cypermethrin is ineffective for perifocal treat-ment and does not give more that 1 wk of controlfor Ae. aegypti. The results were compared withprevious studies using fenitrothion 40 WP appliedat 1 g AVm'�.

298 JouRNnl op rHe Alaenrcnt Mosqurro CoNrnol Assocrlrron Vor- . 16 . No.4

Evaluation of the residual effectiveness oftemephos 19 against Aedes aegypti larvae in

Rio de Janeiro State. Brazil

I. A. Braga, A. K. Ribeiro Galardo andS. da Silva Soares

Fund. Nac. de Saude, Brasilia and Rio deJaneiro, Brazil

Temephos 1g has been used in Brazil for the con-trol of Aedes aegypti for more than 15 years. Re-portedly this formulation has a residual effect ofapproximately 3 months. The duration of effective-ness was evaluated in 55 houses in 2 municipalitiesin Rio de Janeiro State using paired tire sectionlarvitraps. One larvitrap was treated with temephos1g at a rate of 1 ppm and the adjacent larvitrap wasused as an untreated control. Traps were inspectedweekly and larvae were removed and counted frompositive traps before the original water level wasrestored. Tests were also conducted in a series ofstandard water tanks containing 20O liters of waterand treated once with temephos at 1 or 2 ppm. Thi-als were conducted with and without partial waterreplacement to simulate normal household usage.Once a week for 5 wk, larvae were introduced tothe tanks and mortality was recorded after 24 h.The results indicated that larvitraps treated with te-mephos became positive for larvae in 4 of the 6groups beginning in the 2nd week. The remaininggroups became positive in the 4th week of the test.In the water tank tests that had partial water re-placement, larval survival was noted after the 3rdweek at both concentrations. Water tanks withoutwater replacement did not have any larval survivaluntil the 5th week of the test.

Impact of residual spraying of Cypermethrinon an Aedes aegypti population

Marfa Teresa Macoris Andrighetti, Maria deLourdes da Graga Macoris, Luiz Takaku, VanessaCamargo Garbeloto and Vanusa Cristina Busato

Cir ino

Superintendencia de Control de Endemias,Sewicio Regional de Marilia, Brazil

Residual spraying for Aedes aegypti control inBrazil has been restricted to perifocal spraying inplaces with large numbers of breeding sites. Theobjective of this study was to evaluate the impactof this strategy in urban areas. Ttwo districts of Mar-ilia (Sao Paulo State) with high Ae. aegypti infes-tations were chosen. Rosalia and Nobrega are urbandistricts with about 500 houses each. Vector infes-tation was monitored by the Breteau index and fe-male index (number of females per inspected hous-es multiplied by 1OO). In the summer of 1998, theBreteau indices were 22.6 and 14.5 and female in-dices were 50.9 and 52.6 in Rosalia and Nobrega,

respectively. After the winter, the infestations roseagain and 9OVo of Rosalia houses were treated withCypermethrin (250 CE) in November 1998. In thefollowing months, we observed an increased infes-tation in Nobrega, where the Breateau indexreached the levels of the previous summer (I4.7),whereas in Rosalia it was only 2. The female indexper house reached 20 in Nobrega, whereas the max-imum observed in Rosalia was 4.2. This method ofcontrol should be considered for special situationswhere traditional methods cannot be used.

Evaluation of resistance of Aedes aegypti totemephos in Rio de Janeiro State, Brazil

I. A. Braga, A. K. Ribeiro Galardo, A. CostaGarcia and J. Bento Lima

Fund. Nac. de Saude and Inst. Biol. do Exercito.Brasilia and Rio de Janeiro, Brazil

Temephos susceptibility was evaluated in 7 mu-nicipalities in Rio de Janeiro State. This insecticidehas been used intensively to control dengue epi-demics since 1986. Aedes aegypti were collectedand pooled from several locations in each com-munity using enhanced Centers for Disease Controlovitraps, and the F, generation was compared witha standard Rockefeller strain using the diagnosticdosage of 0.012 mg active ingredient/liter. The re-sults indicated the presence of resistance in all ofthe municipalities evaluated. The resulting mortal-ities were 23Vo for 56o Gongalo, 32Vo for Rio deJaneiro, 34Vo for Niter6i, 34Vo for Caxias, 44Va forSdo Jo6o de Meriti, 58Vo for Novo Iguagri, andT4Vofor Campos. The Rockefeller strain had a mortalityrate of lOOVo.

Different levels of insecticide resistance inlarvae and adults of Aedes aegypti from

Venezuela

D. M. Molina de Ferniindez, MagdalenaRodriguez and Juan Bisset

Sertticio Aut6nomo de Altos Estudios en SaludPublica "Doctor Arnoldo Gabald6n." Ministerio

de Salud y Desarrollo Social, Maracay,Venezuela; and Instituto de Medicina Tropical

"Dr. Pedro Kouri," Havana, Cuba

Since 1989, malathion has been the principal ad-ulticide and temephos has been the principal lar-vicide used for controlling Aedes aegypti in Vene-zuela. As a result, advlt Ae. aegypti have becomeresistant to malathion but no temephos resistancein larvae has yet been detected. Nine field strainsof Ae. aegypli from 9 states from Venezuela werebiossayed to malathion and other organophosphateand pyrethroid insecticides. No malathion resis-tance was detected in larvae in any of the strainsevaluated, whereas adults from the same strains

DrceNasen 2000 Svuposruu oN MoseulTo Coxrnol tI.t LertN Aurnrcn 299

showed high levels of resistance to malathion, us-ing the diagnostic dose recommended by the WorldHealth Organization. In addition, some adult resis-tance was found to fenitrothion and some cross-resistance to 1 carbamate (propoxur) in the 9 strainstested. Incipient resistance to pyrethroids has beenfound in 9 field strains of Ae. aegypti from Vene-zuela in both larvae and adults. In vivo analysis ofresistance mechanisms suggest that esterases andmixed-function oxidase cause resistance in larvae.We are investigating the resistance mechanism thatis involved in generating different levels of resis-tance between larvae and adults.

Estimation of insecticide resistance of Aedesaegypti from Trujillo, Venezuela

L. Alvarez Gonzdlez, E. Rojas and J. V. Scorza

Laboratorio de Control del Vectores, Centro deInvestigaciones "J. W. Torrealba," Trujillo,

Venezuela

Dengue and its severe form, dengue hemorrhagicfever, are transmitted by Aedes aegypti, and havebecome an important worldwide public health prob-lem. Unfortunately, this vector has demonstratedresistance for DDT, dieldrin/benzene hexachloride,organophosphates, and carbamate insecticides indifferent states of Venezuela. In Trujillo, Ae. ae-gypti has exhibited resistance against propoxur andlambdacyhalothrin. Resistance to the carbamatepropoxur was found to be low (5.2-fold) and resis-tance to lambdacyhalothrin was moderate (9.6-fold). Susceptibility to malathion was found (2.9-fold). These results must be considered in the futurefor Ae. aegypti control programs because organo-phosphates and pyrethroids are currently used invector control in most countries of Central andSouth America.

In vitro assay of lambdacyhalothrin in twopopulations of Aed.es aegypti from Trujillo,

Venezuela

L. Alvarez Gonzdlez, E. Rojas and J. V. Scorza

I-aboratorio del Control de Vectores, Centro deInvestigaciones "I. W. Torrealba," Trujillo,

Venezueln

Aedes aegypri populations collected from 2 lo-calities in the state of Trujillo, Venezuela, werestudied for their susceptibility for the pyrethroidlambdacyhalothrin. Fourth-stage larvae from bothstrains (IVSS and San Martin) were used for a bio-assay test and their median lethal concentrationswere estimated. When these strains were comparedwith the reference strain (Rockefeller), we found alow resistance with the strain IVSS @.24-fold) anda moderate resistance with the San Martin strain(9.6-fold). These data should be considered in the

selection of insecticides to be used in Venezuelaagainst Ae. aegypti.

Cross-resistance to pyrethroid andorganophosphate insecticides, selection with

temephos in Aedes aegypti from Cuba

M. M. Rodriguez, J. Bisset, M. Ruiz and A. Soca

Instituto de Medicina Tropical "Pedro Kouri,"Havana. Cuba

A strain of Aedes aegypti from Cuba was sub-jected to temephos selection to evaluate the useful-ness of this organophosphate insecticide for mos-quito control. High resistance developed after 6generations of selection. Little or no cross-resis-tance was observed to several organophosphates(malathion, fenitrothion, and fenthion), but highcross-resistance was found to the pyrethroid delta-methrin. Esterases and glutathion-S-transferasecould be the resistance mechanisms responsible forthis phenomenon.

Negative factors affecting dengue controlprograms in Guadalupe, Nuevo Le6n, M6xico

K. M. Valdez, H. Quiroz, V. A. Rodriguez,K. L. Saavedra, F Gonzalez and M. A. Rodrfguez

Inboratorio de Entomologfa, Facultad de CienciasBiol6gicas, Universidad Aut6noma Nuevo Le6n,San Nicolds de los Garza, Nuevo Ledn, Mixico

Socioeconomic level and knowledge about den-gue are 2 factors that adversely affect public healthcontrol programs. Pareto graphics can be used todetect these problems. Surveys were conducted todetect negative factors that affect dengue controlprograms. Two hundred people were surveyed inGuadalupe, Nuevo Le6n. The survey included 25questions about dengue, mosquito breeding, mos-quito control, and other factors. The most notableresult was that people with low salary (about US$200 per month) did not wony about dengue butwere concerned about how to get more money tocover their basic needs such as housing and food.

Use of copepods (Mesocyclops longisetus) in theAedes aegyplC control program of Cali,

Colombia

Marcela Su6rez, Marco E Sur4rez and MariaEugenia Cuadros

Departamento de Biologia, Universidad del Valleand Secretaria de Salud Publica Municipal, Cali,

Colombia

Dengue is considered the most important arbo-virus disease in the world. Because of the absenceof a vaccine, lack of specific medical treatment, and

300 JounNll oF THE AMERTcAN Moseurro CoNrnol AssocurroN VoL . 16 , No .4

limited long-term vector control effects, creativeapproaches should be tested. In Cali, with its 2 mil-lion inhabitants, dengue cases were drastically re-duced with integrated and selective vector controlstrategies, including biological control. The prima-ry Aedes aegypti breeding places in Cali are catchbasins. They almost always contain water, providea good environment, and have larval food through-out the year. They produce 27 times more pupaethan all other breeding places combined. Aedes ae-gypti populations in Cali are resistant to temephos,one of the most commonly used larvicides. Meso-cyclops longisetus, a copepod, was mass producedand approximately 500 specimens were placed ineach catch basin. In 1999,412 basins were treated.None of the treated basins had Ae. aegypti Tarvaeafter 3 months ofcopepod use. This effect extendedas long as 6 months after treatment. Copepods areable to maintain the basins free of Ae. aegypti forextended periods of time if external contaminantssuch as car oil are not present.

The use of palm-sized computers inentomological surveys of Aedes aegypti in

Barbados: pilot project

Marco E Sur{rez, Dale Ifill and EmersonYearwood

Pan American Health Organilation, World HealthOrganization and Vector Control Unit, Ministryof Health and the Environment, Barbados, West

Indies

This pilot study was initiated to examine the util-ity of palm-sized computers as an appropriate tech-nology to improve data and information manage-ment for the reduction of mosquito infestationlevels in Barbados. Ttaditionally, health inspectorsvisit hundreds of houses and record data on the sta-tus of mosquito breeding sites on paper. The vol-ume of the data collected is often quite large, mak-ing it difflcult to associate and summarize rapidlyand produce meaningful information that can beused to make appropriate decisions about vectorcontrol interventions. An electronic version of thetraditional paper data collection form was createdand enhanced on a Casiopeia palm-sized computer.For this study, 10 health inspectors were trained touse the palm-sized computers in the fleld. During asurvey and evaluation period of over 6 wk, 2 palm-sized Windows CE Casiopeia computers with 16MB of memory were used. Based on a question-naire designed to evaluate the ease of use and ac-ceptability of these machines by health inspectorsin their field work, a comparison was made betweenpalm-sized computers and traditional data collec-tion, classification, and summarization techniques.A database report was designed for a desktop com-puter to summarize data and produce the standardindices used for measuring mosquito infestations.

As in other industries, such as electrical utilities.data will be captured and recorded electronically atthe point of inipection, thus minimizing errors dueto recording and subsequent transfer.

Aedes albopictus andl its association with Aedesaegypti in Allende, Nuevo Leon, Mexico

Juan de Dios Aguilar-Gueta, Roberto Mercado-Hern6ndez and Ildefonso Ferni{ndez-Salas

Facultad de Ciencias Biol6gicas, UniversidadAut6noma de Nuevo Le6n, San Nicokis de los


Aedes albopictus has been reported in northernMdxico since 1988. This paper reviews the Ae. al-bopictus-Ae. aegypti association in Nuevo Le6n.During the colonization phase, we assumed that thepresence of Ae. albopictus was associated with Ae.aegypti. For this study, 175 ovitraps were placedfrom December 1998 through August 1999 in sev-eral zones of Allende, Nuevo Le6n, including lo-cations with high, medium, and low mosquito den-sity. All mosquito larvae were collected andidentified. Aedes albopictils was recorded in April1999 and subsequently in other zones. ThroughJuly, no association between the 2 species wasdemonstrated (c? : 3.30, P > 0.05), and Ae. al-bopictus was more abundant.

Preliminary incrimination of Calex(Me lanoc o nion) v omerifer, Cx. (M el.\ adame si,

and Cx. (Mel.) pedroi as enzootic vectors ofsubtype ID Yenezuelan equine

encephalomyelitis viruses in a sylvatic focus inthe Magdalena River Valley, Santander,

Colombia

C. Ferro, J. Boshell, M. L. Ahumada,M. Gonzalez. S. P6rez and S. C. Weaver

Instituto Nacional de Salud, Santa Fe de Bogotd,Colombia; and University of Texas, Medical

Branch, Galveston, TX

As part of studies to delineate the generation ofepizootic Venezuelan equine encephalomyelitis vi-rus (VEE) from enzootic progenitors, field studieswere caried out in an active and continuous focusof enzootic subtype ID virus transmission in a for-est in the Magdalena Medio River Valley, Colom-bia. Hamster-baited traps were used to monitor vi-rus circulation and to identify natural enzooticvectors. Mosquitoes were collected daily for lst 6days after hamster exposure or until hamster death.When VEE was isolated from a sentinel hamster,mosquitoes from positive traps were sorted by spe-cies and pools were tested for VEE. Generally, thelst or 2nd day's collection contained a pool with asingle infected mosquito species, representing theincriminated vector, whereas the last day's collec-

DECEMBER 2000 SyMposruM otr Moseurro CoNrnor- rN LlrN Aur,nrcn 301

tion before hamster death contained pools that wereall infected because of viremic blood meals. Initialvector incrimination results were Culex (Melano-conion) vomerifer, 3 natural transmissions; Cx.(Mel.) adamesl, 1 transmission; and Cx. (Mel.) ped-roi, I transmission. These results challenge thedogma that a single mosquito species serves as theprincipal enzootic VEE vector in a given focus.

New record of Pseadouroctonus redelli(Scorpiones: Vaejovidae) in M6xico

C. Solis-Rojas, J. J. Flores-Maldonado,C. B. Ramos-Silva, H. Quiroz-Martinez,

R. M. Gonz6lez-Iglesias and R. Garza-Cantf

Facultad de Ciencias Biol6gicas, UniversidadAut6noma de Nuevo Le6n, San Nicokis de los

Garza, M€xico; and Departamento de RecursosNaturales, Instituto de Estudios Superiores,

Monterrey, Nuevo Le6n, Mixico

M6xico's vaejovid scorpion fauna is one of themost diverse in the world. A small percentage ofthe members of this family is known because of thelimited investigations that have been conducted innortheastern M6xico. Vejovis, Serradigitus, Fran-keus, and Paruroctonus are the genera reported forthis family in this area. We examined 1,000 speci-mens of the family Vaejovidae and preserved themin the arachnid collection of the Biological ScienceFaculty-UANL . P s e udouro ctonus rede lli is report-ed as a new record in several localities of the statesof Nuevo Le6n and Coahuila, Mdxico. The speci-mens of P. reddelli were collected at elevations be-tween 8OO and 1,550 m and identified with keys ofGertsch and Soleglad (1972) and Stockwell(1992).

Presence of C entruroide s ele gans (Scorpiones :Buthidae) in Nuevo Le6n, M6xico: a new

distribution record?

C. Solis-Rojas, J. J. Flores-Maldonado,K. Arevalo-Niflo, S. Morales-Arroyo,

W. A. Albeldaflo-Yflzqtez and I. Iracheta-'famez

Facultad de Ciencias Biok5gicas, UniversidadAuton6ma de Nuevo Le6n, San Nicolds de los


Members of the family Buthidae are among themost medically important scorpions in the Ameri-cas because of their sting. The genus Centruroidesbelongs to this family and is found exclusively inthe Americas. Some of the central states of Mexicohave some of the most toxic scorpion speciesknown. In these areas, scorpion envenomization isconsidered one of the most important public healthproblems and high human mortality is reported inthis region. Centruroides vittatus and C. gracilis arcnative scorpions in Nuevo Le6n. However, since198O. Centruroides elesans, one of the most toxic

scorpions in Mexico, has also been reported in thisstate. Approximately 5,000 specimens of Buthidaewere reviewed from the arachnid collection at theBiological Science Faculty at the State Universityof Nuevo Le6n. The specimens were identifled us-ing keys written by Hoffman. Centruroides elegansmay have arrived in Nuevo Le6n State by trans-portation of fruit products, and not as a general ex-pansion of its previous range.

Morphometric comparison among Triatomalongipennis (Hemiptera: Reduviidae) from the

west coast of M6xico

Jos6 A. Martfnez-Ibarra, Jesris Romero-N6poles,Ricardo Alejandre-Aguilar, Gabriel Rinc6n-

Enriquez and Juan C. Zaragoza-Ramirez

Ins tituto Fitosanidad, Co le gio Post g raduado s andLaboratorio Parasitolo gia, Escuela Nacional

Ciencias Biologicas and Laboratorio MarcadoresGeneticos, Texcoco de Mora, Mexico

Triatoma longipennis is one of the most impor-tant vectors of Trypanosoma cruzi (the cause ofChagas' disease) to humans in western M6xrco.Some ethological differences were detected in vec-tor populations sampled from 7 localities across itsrange along the west coast of M6xico. Five mea-surements were performed on 10 adults from eachof these populations. The populations were not sta-tistically different (P > 0.05) morphologically, andthey were concluded to represent a single popula-tion in spite of the different ethological habits re-corded.

Epidemiologic and entomologicalcharacterization of a leishmania focus in

Venezuela

M. Dora Feliciangeli, Jazzmin Arrivillaga, lrmaAgrela, Noris Rodriguez, Olga Zerpa, Angela

Hamilton, Josd Plata and Leyda Gudiflo

Universidad de Carabobo, Aragua, Maracay;Instituto de Biomedicina. Caracas: Servicio de

Dermatologfa Sanitaria, La Grita; andMalariologia, San Felipe, Venezuela

Cutzureous leishmaniasis (CL) in Venezuela isscattered all over the country but mainly concen-trated in the foothills of the Andes and the Serraniade la Costa. with an elevational distribution fromsea level to 2,800 m. From 1955 to December 1998,a total of 41,250 cases of CL were registered bythe National Department of Dermatology, now theVenezuelan Institute of Biomedicine. American vis-ceral leishmaniasis (AVL) in Venezuela is foundmainly in 3 areas: in the east (the island of Mar-garita and states of Sucre and Anzoategui), in thecenter (Aragua, Carabobo, Gu6rico, and Cojedesstates). and in the west from Lara State to Zulia

302 Jourunl oF THE AMERIcIN Mosquno CoNrnol AssocrlnoN Vol. 16, No. 4

State. A total of 925 cases were reported from 1955to 1998. Howeve! underreporting is common and,as for CL, true figures may be at least 3 times thenumber that has been reported. We have studiedseveral foci of CL and AVL in Venezuela and gath-ered evidence on domestic and peridomestic trans-mission that is supported by epidemiologic and en-tomological data. The epidemiologic criteria forcharacteization of foci includes the distribution ofthe disease among the population in relation to de-mographic and social characteristics, which helpsin the definition and recognition of risk factors.Long-term temporal (seasonal) and spatial (indoorsand outdoors) catches of phlebotomine sand flyspecies tested by the dot-enzyme-linked immuno-sorbent assay have shown that humans are the mainsource of blood meals. Further, naturally infectedsandflies wit}r Leishmania spp. were found to beindistinguishable from those collected from peopleliving in endemic foci. Lutzomyia ovallesi, L. pan-amensis, L. gomezi, L. spinicrassa, and L. youngiare recognized as the vectors of LC and L. longi-palpis ard L. evansi as vectors ofAVL. Techniquessuch as geographic information systems will allowthe stratification of the leishmaniases in Venezuelaand will be helpful in the decision-making processfor prevention and control of the disease and pro-duce a more adequate allocation of resources. Thiswork was supported by a Venezuelan Government-World Bank project (PCEE-VEN.964O2).

Chagas' disease and leishmaniasis: new toolsfor control of vector-borne diseases

E. Villegas-Avila

Inboratorio de Control del Vectores, Centro deInvestigaciones "J. W. Torrealba," Trujillo,

Venezuela

Vector-borne diseases represent a significant pub-lic health problem for many countries. Among thediseases that have shown a recrudescence in recentyears are malaria, Chagas' disease, schistosomiasis,onchocercosis, dengue, fi lariasis, leishmaniasis, andencephalitis. The use of control measures such asspraying of the dwellings with insecticides is acommon measure for controlling vector-borne dis-eases. This control measure involves different prob-lems: high cost of insecticides, support of highlyspecialized personnel, economics, and politics. Theuse of insecticide-impregnated curtains and bednetsto interrupt the human-vector contact have beenimplemented as new advances for control of vector-borne diseases. The efficacy of this measure hasbeen demonstrated against different species ofbloodfeeding mosquitoes. In Latin America, mos-quito nets and curtains were used in Colombia andVenezuela for control of Chagas' disease and leish-maniasis. This method was very effective in reduc-ing the number of Rhodnius prolixus ^nd Lutzomyia

youngi. The use of mosquito nets and curtains is apromising technique for the control of vector-bornediseases.

Characterization of Anopft eles breedinghabitats in Sifontes, Bolivar State, Venezuela

Jorge E. Moreno

Divisi6n de Investigaciones, Escuela deMalariologia y Saneamiento Ambiental "Dr.

Arnoldo Gabald6n," Maracay, Venezuela; andCentro de Investigaci6n de Campo "Dr.

Francesco Vitanza, " Bolivar, Venezuela

Sifontes is a city in northeastern Bolivar Stateand is the main focus of malaria in Venezuela.From 1992 to 1998, an average of4,180 cases wasreported annually from this area, where mining isthe principal activity. To locate and.identify Anoph-eles breeding sites and to determine the species pre-sent in this area, a longitudinal study was initiatedin the localities of Las Claritas, El Dorado, SanMartin de Turumb6n, Tumeremo, and Bochinche.Anopheles larvae were collected with a dipper andlater identified to species. Some physicochemicaland botanical observations were made of the breed-ing site. Twelve species of Anopheles plus Chaga-sia bathana were collected. Of these, 6 belong tothe subgenus Nyssorhynchas, 5 to the subgenusAnopheles, and 1 to the subgenus lttphopodomyia.The most abundant species in the area is An. trian-nulatus, followed by An. marajoara. ^Ihe main vec-tor of the area, An. darlingi, is not very abundantbut is widely distributed. Canonical correspondenceanalysis allowed us to determine the decisive bioticand abiotic factors influencing the presence, abun-dance, and distribution of these species.

Anopheles albilnanus mortality in anindigenous area of Panama

Argentina Y. de Turner, Gloria de Obaldia,A. Garcfa and C. Campos

University of Panama, Panama CanalCommission, and the Ministry of Health, Panama

City, Panama

Problems of insecticide resistance in Anophelesalbimanus, the main malaria vector in an indige-nous area dedicated to agriculture and cattle, werestudied. The incidence of malaria in this area hasprogressively increased since 1993, and the numberof cases of malaria doubled in 1998 compared withthe same dates for 1997. The study area was in theprovince of Bocas del Toro, located on the Atlanticcoast, 500 km west of Panama City. It is a ruralarea with houses of mud and palm trees or of woodand zinc and has an average temperature of 28'Cand a relative humidity of 85Vo. Over a l-year pe-riod, we made 2,64O biological assays on walls to

DscBNasen 2000 SyMposruM oN Moseurro CoNtnol rN LATIN AMERICA 303

evaluate resistance of k-othrine (deltamethrin, 57o)on the different surfaces. In the area, we evaluatedthe percentage of mortality in 39,600 female An.albimanus collected with human bait. We found anaverage 78Vo mortality with a residual effect of 34wk during the lst 6 months and93Vo mortality with28 wk of residual effect.

Comparison of four methods for collectingadult anopheline mosquitoes from a malaria

endemic area in Rondonia. Brazil

E Santos, J. B. P Lima and I. A. Braga

Fundagdo Nacional de Saide and USAMRU/B,Brasilia, Brazil

For many years, the most common method forcollecting anopheline mosquitoes has been the hu-man biting collection, but this method increases thechances of contracting malaria. Four methods werecompared in the endemic malaria area in Porto Vel-ho, Rondonia, Brazil. These included the Shannonmodified trap, the Shannon trap with a light source,a person using a black cotton sock, and collectionson human legs. These methods were used outsideat 4 locations at 4 times during 1998. Human bitingcollections proved to be more effective than othermethods. The most abundant species collected wasAnopheles darlingi. The nulliparous rate was sig-nificantly higher than that of the parous rate in allmethods. These results showed that for monitoringanopheline populations, the best method was thehuman biting collection; however, other effortsshould be made to find an alternative method thatdoes not compromise the health of the human vol-unteers.

Morphologic effects in Anophelesps eudopunctipennis (Diptera: Culicidae) caused

by control strategies in an artificial pool

F. Gonzdlez, H. Quiroz, V. A. Rodriguez,L. M. Villegas, L. O. Tejada and M. H. Badii

Laboratorio de Entomologia, Facultad deCiencias Biol1gicas, UANL, and Programa

Graduado de Agricultura, San Nicokis de losGarza, Nuevo Le6n, Mdxico

We used Bactimos (Bacillus thuringiensis var. rs-raelensis [Bti]) and Buenoa scimitra as controlstrategies alone and together against anophelinemosquitoes and studied their effect on survivingmosquito larvae in an artificial pool. The treatmentsapplied were Bti, B. scimitra, Bti plus B. scimitra,and control. Our test systems were 2O 3rd- and 4th-stage Anopheles pseudopunctipennis larvae. After24 h of exposure, mortality was recorded and sur-viving larvae were taken to the laboratory, whereadults were reared. Body measurements were takenand the data were analvzed statisticallv with anal-

ysis of variance. A statistically significant differ-ence was found among treatments (P < 0.05) andmortality was similar among the treatments. Ninetyadults were obtained, including 35 females and 55males. Female body measurements were 8.92-mmhind legs, 4.33-mm thorax-abdomen, and 3.80-mmwings.

Effect of algal extraction on Anophelesps eudopunctipennis larval populations in

southern Chiapas, M6xico

Juan G. Bond-Compeiin, Juan I. Arredondo-Jim€nez and Mario H. Rodriguez

Centro de Investigaciones Paludismo, InstitutoNacional de Salud Prtbhca, Tapachuln, Chiapas,

M€xico; and Centro de Investigaciones SobreEnfe rme dade s Infe c cio sas, Instituto Nac ional de

Safud Prtbhca, Cuernavaca, Morelos, Mdxico

We investigated the effects of mechanical extrac-tion of filamentous algae on the dynamics ofAnopheles pseudopunctipennis larvae from riverpools of southern Chiapas, M6xico. The study tookplace throughout a dry season, over a 6-km river-wide belt transect divided in 500-m sections. Six ofthese 500-m sections were selected randomly andassigned to be treatments (where all algal matswere mechanically extracted) or controls (where thenormal dynamics of algal mats were followed).Anopheles pseudopunctipennis larvae from aU beltsections were monitored fortnightly. A total of 138larval habitats distributed along the 6 transects werecounted. They were composed of 2 green algaegenera, Spirogyra (at early succession of the algalmat) and Cladophora (at later stages of succession).The extraction of algal mats had a significant effecton the reduction of An. pseudopunctipennis larvae(F : 31.98, df : 5, P < 0.001), with an overallmean of 2.5 larvae/dip in the treatment belt sectionsand 11.4 larvaeldip in the control. Total mosquitolarval control lasted for 45 days postextraction.This complementary, naturalistic vector control tac-tic is now being implemented with excellent resultsby the National Malaria Control Program throughcommunity participation.

Innate host preferences in Anophelesvestitipennis

Armando Ulloa, Juan I. Arredondo-Jimdnez,Mario H. Rodriguez and Ildefonso Fernrlndez-

Salas

Centro de Investigaciones de Paludismo, InstitutoNacional de Salud Piblica, Tapachula, Chiapas,Mdxico; Centro de Investigaciones Enfermedades

Infecciosas, Instituto Nacional Salud Prtbhca,Cuernavaca, Morelos, Mixico; and Laboratoriode Entomologia Medica, Universidad Autonoma

de Nuevo Le6n, San Nicolds de los Garza, NuevoLe6n, Mdxico

We assessed the existence of innate host prefer-ences in Anopheles vestitipennis using F, mosqui-

304 JounNer- op"ufi AvEnrcaN Mosquno CoNrnol Assocrnrroll Vor . 16 , No.4

toes from parental females with known feeding his-tories. The study was conducted in southernChiapas, M6xico, in an experimental hut construct-ed with local materials and divided into 3 com-partments, each lined inside with netting. The sidecompartments were occupied by 2 humans and Ihorse, 1 cow, or 2 pigs. Two types of experimentswere conducted: 1 with females collected unfed andreleased in the experimental hut, and I with F, fe-males collected from animal or human hosts. Mos-quitoes of each population were marked with dif-ferent fluorescent dust colors. Mosquitoes werereleased from the central room at l93O h, with hostsalready positioned, and recaptured from each com-partment at 0500 h. We recorded the number ofmarked bloodfed and unfed mosquitoes selectingeach host. Using wild-collected mosquitoes, the re-capture rates on the human or animal compartmentwere 24 and 76Vo, respectively (X' : 427.84, p =0.0001). With Fr mosquitoes, we released

'773 and

522 anthropophilic and zoophilic mosquitoes, re-spectively, whereas recapture rates were 59 andSOVo (y2 : 61.66, P : O.OO01). These results con-firmed the existence of innate host preferences inAn. vestitipennis.

Comparative study of the genetic identity ofsympatric and allopatric populations of

Anopheles vestitipennis using random amplifiedpolymorphic DNA-polymerase chain reaction

techniques

Juan I. Anedondo-Jimdnez, Hortensia Murillo-Sdnchez, Fidel C. Herniindez, Cuauht6moc

Villarreal and Mario H. Rodriguez

Centro de Investigaciones de Paludismo, InstitutoNacional de Salud Prtbhca, Tapachula, Chiapas,

Mdxico ; Laboratorio Entomolo gia Molecular,Centro Investigaciones y Estudio Avanzados,

Mdxico Distrito Federal, Mdxico: and Centro deI nv e s t i g ac ione s S o b r e Enfe rme dade s I nfe c c io s a s,Instituto Nacional de Salud Publica, Cuernavaca,

Morelos, Mixico

Our aim was to gather evidence to support thehypothesis of the existence of anthropophilic andzoophilic populations w ithin Anophe le s v e s titip en-nis. To do this, we investigated the presence ofran-dom amplified polymorphic DNA markers thatcould differentiate mosquitoes collected on humanand animal hosts. After an inititial screening of 62random primers (kits A, B, C, and D, Operon Tech-nologies, Alameda, CA), 10 primers (A08, AO9,Al4, Al7, BO4, B05, COl, ClO, Cl3, and DOl)produced 21 consistent polymorphic markers thatwere chosen for further analysis of indoor humanlanding and animal bait populations from 4 villagesof Chiapas (3) and Tabasco (1) states. Nei's geneticdistance (Nm) found :rmong An. vestitipennis hu-man landing and animal bait collections averaged

0.2318, with smaller genetic distance between an-thropophilic mosquitoes (0.2050) than among zoo-philic mosquitoes (0.2487). The variance in allelefrequency, Wright's F statistic, averaged O.32 -+

0.16, and effective migration rate Nm was {1 in14 of 2l studied markers, averaging 0.5, or I mi-grant individual every 2 generations, which indi-cates a restricted gene flow. The dendrogram of ge-netic distances yielded 2 branches, grouping 3 of 4anthropophilic populations in I branch and 3 of 4zoophilic populations in the other branch. Thesefindings provide additional evidence to the exis-tence of a species complex within An. vestitipennis.

Gene flow among Anopheles albimanuspopulations as determined by random

amplified polymorphic DNA-polymerase chainreaction in M6xico

C. Villarreal Trevifro, J. I. Aredondo-Jim6nezM. H. Rodriguez L. and I. Malo-Garcia

Centro de Investigaciones de Paludismo, InstitutoNacional de Salud Piblica, Tapachula, Chiapas,

Mdxico; and Centro de Investigaciones SobreEnfe rme dade s Infe c c io s as, Instituto N acional de

Salud Publica, Cuernavaca, Morelos, Mdxico

The gene flow among populations of the malariavector Anopheles albiman r was investigated byamplification of random regions in genomic DNAusing random amplified polymorphic DNA (RAPD)markers (RAPD-polymerase chain reaction). Vari-ation patterns in gene flow among neighboring anddistantly located populations were investigated bystudying 20 populations collected from variousagroecological areas of southern Chiapas, M6xico,and 10 populations collected from various states ofMexico (9) and Guatemala (l). After an initialscreening of 6O random primers (kits A, B, and C,Operon Technologies, Alameda, CA), 5 primers(A05, A20, B04, Bll, and 818) produced 47 con-sistent polymorphic markers for microgeographicanalysis, whereas for the macrogeographic analysis,7 primers (A05, A08, Al2, AI9, A20, B04, andB1l) that produced 54 markers were selected. InChiapas, the average F statistic value was 0.117 -f

0.073 and Nm : 1.9 migrants/generation, whereasin Mexico, the average F statistic was 0.1967 +

0.141 and Nm : 1 migrants/generation. The den-drogram of Chiapas indicated incipient clusters oflocalities by agroecological areas, whereas the den-drogram of macrogeographic analysis yielded 2principal clusters, I from the northern states ofMexico and the other from the south. The smallnumber of migrants could explain the focalizationof malaria transmission in M6xico.

Decrvnen 200O Svttlposrurrr oN MoseulTo CoNrnoL tl LerrN Auenlcl 305

Raw plant extracts influencing oviposition inAnopheles albbnanus under laboratory

conditions

Jos6 L. Torres-Estrada, Rosa A. Meza-Alvarez,Juan Cibrir{n-Tovar, Juan I. Arredondo-Jimenez,Leopoldo Cruz-L6pez and Mario H. Rodriguez

Centro de Investigaciones de Paludismo, InstitutoNacional de Salud Piblica, Tapachula, Chiapas,

M€xico; Instituto de Fitosanidad, Montecillos,Mixico; El Colegio de la Frontera Sur,

Tapachula, Chiapas, Mdxico; and Centro deI nv e s t i g ac io ne s S o b re E nfe rme dade s Infe c c i o s as,Instituto Nacional de Salud Priblica, Cuernavaca,

Morelos, Mdxico

Some plant species are very attractive as ovipo-sition sites for some anopheline species, indicatingthat such places are specifically selected by gravidfemales that are guided using chemical cues re-leased from the larval habitat, perhaps from plants.In this investigation, we assessed the effect of rawaqueous extracts of aquatic plants on the oviposi-tion behavior of Anopheles albimanus in southernChiapas, M6xico. Aqueous extracts of 5 plant spe-cies were tested at 6 concentrations (50, 10, 1, 0.1,0.01, and O.OOLVo dilutions), compared to plain wa-ter. Five replicates per plant species of 2 dishescontaining 20O ml of each treatment were set side-by-side in a cage containing 30 gravid An. albi-manus females. Dishes were inspected for eggs af-ter 24 h. Results indicated that 50 and 107o plantextracts elicited repellence (Brachiaria mutica,Fimbristylis spadicea, Cynodon dactylon, Cerato-phyllun demersum, an,d Jouvea straminea), whereasplant extracts at 0.01 artd O.OOlVo concentrationsshowed an attraction response. These results indi-cate that some plants need to be studied in detailfor their attraction or repulsion properties towardsgravid An. albimanus females. Gas chromatogra-phy-mass spectrometry analysis showed mixed ter-penoid and alcohol compounds of aqueous extracts,including guaiacol, phenol, isoeugenol, longifolene,caryophyllene, phenyl ethyl alcohol, and p-cresol.

Residual effect of Bacillus sphoericus(Vectolex@ CG) for the control of Anopheles

darlingi in Iquitos, Perri

Ernesto Berrocal, Cristiam Carey, Luis Rodriguez,Carlos Calampa and Luis Valdivia

Direccidn Regional de Salud Loreto, Ministeriode Salud del Perrt, Iquitos, Perrt

The proliferation of fish farms at the communitylevel has provided suitable breeding sites forAnopheles darlingi, the main malaria vector in theregion of Loreto, in northeastern Perf. Eight fishfarms and I natural pond with active An. darlingibreeding, which had no history of larval control

measures, were selected at 3 localities near Iquitos.Two of the breeding sites were used as untreatedcontrols and 7 of the sites were treated with a gran-

ular formulation of Bacillus sphaericus (Vectolexo

CG, supplied by Abbott Laboratories, North Chi-cago, IL) at rates of 5, 10, and20 kg/ha by manualapplication. Larval populations were monitoredweekly for I month before application, and at 1,2,3,7, 14,21,30, and 45 days postapplication. Onehundred percent reduction of all larval instars wasobtained by 2 days postapplication in all treatedsites. Residual control was maintained for up to 45days, as measured by the presence of late instars.No evidence was found of adverse effects on thefish. Because of the ease of use, this granular for-mulation of B. sphaericzs offers a promising toolfor community-based control of An. darlingi.

Larvicidal effect of Bacillus thuringicnsis var.israelensis H-14 (Bti) in fish-farm ponds near

Iquitos, Peni

P. Ventosilla, J. Chauca, H. Guerra, J. Merello,B. Infante, C. Calampa, J. Arambuni, H. Jab6,

J. Gonzales, W. Tello, E. Ruiz, D. Ar6valo,C. Ramal and R. Naupay

Instituto de Medicina Tropical Alexander vonHumboldt, Universidad Peruana Cayetano

Heredia, Lima, Peril; and Direcci6n Regional d.eSalud de Loreto, Iquitos, Peri

Bacillus thuringiensis var. israelensis (Btl) is oneof the most successful bacterial entomopathogensused for controlling insect vectors of human diseasepathogens. We report on the toxic effect of a com-mercial Bri formulation on Anopheles larvae in thefield. Assays were performed in Quistococha, Lor-eto, Perri, using Vectobac G Abbott (200 ITU/mg),donated by Rivers of the World. The Bti was hand-applied at about 2 glm2 in 5 test fish-farm ponds,whereas 5 other ponds served as controls. All pondswere comparable, as determined by studying theirflora, fauna, soil type, and selected chemical param-eters. We evaluated mortality and duration of toxiceffect per larval instar in Bti-inoculated ponds, andmean fluctuations of larval population in controlponds. The toxic effect of Bri against Anophelestriannulatus, An. nuneztovari, and An. albitarsislarvae lasted (P < 0.005) for 23 days comparedwith initial populations, with l$OVo reductions inall ponds for all larval instars during the lst 4 daysand 99-lOOVo at 7 days. The fluctuation of meanlarval populations was significant (p < 0.005) fordifferent larval instars and different control ponds.If used weekly or even fortnightly, Bti may effec-tively control Anopheles larvae in fish-farm ponds.

306 Jouwer- or rHg AlvtgnrclN Mosquno CoNrnol AssocrarrctN VoL . 16 , No .4

Molecular characterization of B esterase-amplified haplotypes related to insecticide

resistance in Culex quinquefascialzs from Cuba

J. A. Bisset, M. M. Rodrf guez, E. Calvo, C. Diazand A. Soca

Instituto de Medicina Tropical "Pedro Kouri,"Havana, Cuba

Overproduction of esterases is a common insec-ticide resistance mechanism in Culex quinquefos-ciatus. Tlte same amplified haplotypes (e.g., B1 and82) have been found in different regions and alarge polymorphism in the esterase B locus hasbeen reported in susceptible populations, which hasarisen as a migration hypothesis for amplifiedgenes. In this paper, we report the results of restric-tion fragment length polymorphism and restrictionmapping assays on 3 strains of Cx. quinquefoscia-tus from Cuba. These strains were obtained fromnatural populations from Santiago de Cuba and Ha-vana City and another was generated by selectionin our laboratory. The same pattern of amplified B 1haplotypes was detected in mosquitoes from bothstrains, which also was very similar to the amplifiedBl haplotypes of the temephos reference strain, al-though a difference accounted for a,Flindlll site inthe flanking sequences that coamplify with the con-cerned esterase gene. These results suggest a prob-able migration of 81 genes in our country after aninitial event of different ampliflcation that is inde-pendent from the event that generated the amplifiedBl haplotypes in the reference strain. This infor-mation supports the theory of gene migration afterconsidering probable independent amplificationevents of the same gene in different regions underwell-determined conditions.

Oviposition in artificial substrates forChironomus plumosus

B. Medellfn, V. A. Rodrfguez, H. Quiroz,V. Robledo and X. Martinez

Ittboratorio de Entomologfa, Facultad deCiencias Biol6gicas, UANL, San Nicolds de los


Presence of adult midges is 1 cause of econom-ical loss in real estate business and tourism becausechironomids occur in large swarms and can causepanic among residents and visitors. The objectiveof this study was to determine oviposition sites pre-ferred by Chironomus plumosus. White, yellow,red, and green panels were used as artificial sub-strates for C. plumosus oviposition. The panelswere placed in a large pool in a wastewater treat-ment plant and egg masses were taken from eachpanel each week. The egg masses were counted anddifferences were analyzed statistically. No differ-ence was found among the colors (P > 0.05).

Mosquito control strategies in artificialcontainers and their morphologic effects

V. A. Rodriguez, H. Quiroz, L. Torres,F. Gonz6lez, L. O. Tejada and M. H. Badii

Inboratorio de Entomologia, Facultad deCiencias Biol6gicas, UANL, San Nicolds de los


The most acceptable mosquito control strategiesare those with minimum effect on the environment.Many integrated mosquito management programshave been established, but a question that has arisenis what happens to the survivors. The objectives ofthis study were to evaluate the effectiveness of Ag-nique and Buenoa scimitra alone and together asmosquito control strategies in artificial containersand their effects on survivors. The study was con-ducted in 200-liter plastic containers, and 4 treat-ments were applied (Agnique, B. scimitra, Agniqueplus B. scimitra, and an untreated control). Everyweek, 15 samples were taken and the Culex quin-quefasciatus larval densities were recorded. Tfeat-ment differences were tested by analysis of varianceand backswimmers after 3 months. Differences werenot statistically different except in the case of thejoint application of Agnique. A total of 115 Cx.quinquefasciatas adults were obtained; 63 malesMd 52 females. Wing size was similar in all treat-ments.

The mosquitoes of Puerto Rico: distributionand habitats (199!99)

E. A. Kenny-Elliot

Department of Biology, University of Puerto Rico,San Juan, Puerto Rico

The habitat, diversity, and distribution of mos-quitoes in Puerto Rico has not been studied exten-sively. Since 1993,I have collected mosquitoes onthe main island. Preliminary results of these collec-tions include Anopheles albimanus, collected fromlight traps in Cabo Rojo (west coast), and Arecibo(north coast); Anopheles grabhamii, from lighttraps in Cabo Rojo, and larvae from brackishground water in Aflasco (west coast); Aedes tae-niorhynchus larvae, collected from a rainfall muddyground pool at Piflones State Mangrove Forest(north coast) and from light traps at Cabo Rojo,Arecibo (north coast), Fajardo (east coast), and Sa-linas (south coast); Aedes sollicitans, frorn lighttraps next to mangroves at Piflones Forest, Arecibo,and Cabo Rojo; Aedes mediovittatus. from tire trapsat Aflasco and Vega Alta State Forest (north coast),and also from foul water in artificial containers atGurabo (east-central); Psorophora jamaicensis,found in temporary rainpools in Gurabo; Toxorlryn-chites portoricencis, collected in tire traps in Gur-abo mountains, Camuy (north coast), and Guajataca

DECEMBER 2000 SyMposruM oN MoseulTo CoNrnol IN LATIN Auentca 307

State Forest in Quebradilla (north coast); Wyeomyiasp., found in bromeliads at Yunque mountains inRio Grande (northeast coast); Culex quinquefascia-/as, found in foul water in an artificial container atCabo Rojo, Gurabo, San Juan, Fajardo, Maricao(west-central), and Susua State Forest in Yauco/Sa-bana Grande (south-central); Culex secutor, fowdin tire traps, fallen palm bracts, and terrestrial bro-meliads at Yunque forest; Culex janitor, collectedfrom tire traps at Susua forest; and Culex habili-tator, found in brackish ground pools and tire trapsin Afrasco.

Posters

Correlation between premise condition indexand Breteau index

F Espinosa G6mez, C. M. Hernrindez Sudtrez,X. Montoy Guzmdn and I. Ferniindez Salas

Faculty of Medicine, University of Colima,Mdxico; and Department of Medical Entomology,

Faculty of Biological Sciences, UniversidadAut6noma de Nuevo Le6n, San Nicolds de los


To compare the effect of an educational cam-paign (EC) for Aedes aegypti elimination versus ve-hicle-mounted ultra-low volume (ULV) applica-tions of malathion, we examined 187 houses inColima, M6xico, during a 6-month period. Larvaldensities were expressed as positive container/house index (C+/H) and were determined at thebeginning and at the end of the study. Houses weredivided into 4 treatment blocks: A) treated withULV alone, B) control (untreated), C) ULV appli-cation plus EC, and D) EC only. Baseline C+/FIvalues were not significantly different in any block(F : 2.56, P > 0.05). Changes in the C+/H indexat the end of the study were -0.108 for A, +0.31for B, -0.183 for C, and -0.870 for D. A 2-wayanalysis of variance showed a significant reductionin EC vs. control (F : 8.4, P < O.OO42), a morediscrete reduction with ULV (F : 0.38, P > 0.5),and a negative interaction between EC and ULV (F: 6.51, P < 0.01). Our results suggest that an ECis more economical, effective, and sustainable forAe. aegypti breeding site reduction than traditionalULV applications, and that ULV applications couldreduce the efficacy of an EC, possibly by creatinga false sense of security in the community.

The vector control program of the PanarnaCanal Commission (191L2000)

G. D6vila de De Obaldia and O. E. Pinz6n

Panama Canal Commis sion, EnvironmentalDivision, Panama City, Panama

The construction and continued operation of thePanama Canal are made possible through the san-

itation and vector control program developed dur-ing the 86 years of operation that the Panama Canalwill have had in the year 2000. Diseases such asyellow fever and malaria constantly threatened thelabor force of the Panama Canal and the humanpopulation of surrounding areas. We have devel-oped an integrated vector control program that in-cludes the following components: channeling ofstanding water; ditch cleaning; collection and dis-posal of solid waste; monitoring of light traps; col-lection and identification of samples from lighttraps; continued search for new vectors; the elimi-nation of breeding sites using mechanical, physical,

chemical, and biological controls; and an educa-tional and research program in the area. With thissuccessful integrated control program, we have aninteroceanic route free from tropical vector-bornediseases.

Contribution to knowledge of the culicids ofCoahuila. Mexico

S. Vergara Pineda, O. Garcia Martinez andH. Quiroz Martinez

Laboratorio Entomologfa y Acarologfa, CentroNacional Ref. Fitosanitaria Gmo. Pdrez

Valenzuela, Coyoacdn, Mdxico: andDepartamento Parasitolo gia, Unive rsidad

Autondma Agraria Antonio Narro, InboratorioEntomolo g/a, Facultad Ciencias Biol6gicas,

Monteney, Nuevo Le6n, Mdxico

We examined 592 microscope slides of mosquitolarvae and 1,447 pinned adults. From these mate-rials, the following 22 species were identified: Ae-des albopictus, Ae. aegypti, Ae. epactius, Ae. sca-pularis, Ae. trivittatus, Ae. vexans, Ae. Toosophus,Anophe le s franc iscanus, An. quadrimac ulatus, An.pseudopunctipennis, An. punctipennis, Culex ari-zonensis, Cx. coronator, Cx, erythrothorax, Cx.quinquefasciatus, Cx. stigmatosoma, Cx. tarsalis,Cx. thriambus, Culiseta particeps, Psorophora con-

finnis, Ps. signipennis, arrd Uranotaenla sp. Whendiversity indexes were applied, Cx. quinquefascia-fal was the most representative in larval and adultstages, with P, : O.4375 and 0.466, respectively,whereas the least diverse was both larval and adultAn. franciscanrs, with Pr : 0.0016 and 0.0007, re-spectively. We divided the state into 3 zones (north,

center, and south) and an overlapped niche was ob-served for larval stages between north and southzones with Iv = O.9544 and for the adult stage be-tween north and central with I, = 0.9516. Higherdiversity was found for the south zone both for lar-val and adult stages with E : 0.8100 and 0.6689,respectively.

308 Jounull oF THE AMERICnN Mosquno CoNrnol Assocnrrorl Vor . 16 , No.4

Dengue stratification in a hyperendemic cityusing a geographical information system

R. Barrera, N. Delgado, M. Jim6nez, IrisVillalobos and I. Romero

Laborstorio Biologia Vectores, Instituto deZoologia Tropical, Facultad de Ciencias,

Universidad Central de Venezuela, Caracas,Venezuela; Instituto de Zoologia Agricola,

Universidad Central de VeneTuela, Maracay,Venezuela; and Corposalud Aragua, Maracay,

Venezuela

We analyzed the dynamics of dengue transmis-sion in a hyperendemic city. Results were used tostratify the city for control purposes. A geographi-cal information system incorporated the spatial na-ture of the disease and related environmental vari-ables. Analyses were performed at the levels ofcounties (7) and neighborhoods (349) in Maracay,Venezuela, with its population of 1 million people.Variables investigated were dengue incidence,prevalence, and persistence (number of consecutivemonths a locality had cases) from 1993 to 1998;Aedes aegypli house, Breteau, and container indi-ces; pupal production; adult mosquito density; in-habitants; area; quality of water supply and refuseservices; and human mobility. Limits of countiesand neighborhoods, roads, hydrology, and elevationwere digitized from maps (1:5,000). Dengue prev-alence was high (171 dengue and 42 dengue hem-orrhagic fever [DHF] cases per 1O0,O0O ayear;245DHF cases per 1,000 dengue cases) with relativelylow mortality (8 deaths). A temporal analysis re-vealed that the same neighborhoods consistentlyproduced most of the cases every year. The rela-tionship between dengue incidence and persistenceallowed us to make a preliminary stratification ofthe city, so that immediate control would need tobe applied to 34Vo of the area or l57o of neighbor-hoods. Further analyses are under way to determinethe effect of environmental variables on denguetransmission.

Effectiveness of Permanet@ (permethrin 55Vo')-impregnated traps against Chironomas

plumosus

A. Escalera, V. A. Rodriguez, H. Quiroz,K. L. Saavedra, K. Ochoa and E. Melendez

Laboratorio de Entomologfa, Facuhad deCiencias Biologicas, UANL, San Nicolds de los

Garza, Nuevo I*6n, M€xico

The chironomid midge Chironomus plumosus isa special problem in public health because its an-noying swarms continuously cause phobias in peo-ple who live near wastewater treatment plants. Theeffectiveness of Permanet@ (permethrin 55Vo) im-pregnated on metal light traps against C. plumosus

adults was evaluated around a wastewater facilityin San Nicolds de los Garza. Nuevo Le6n. M6xico.Four concentrations of permethrin were used astreatments and they were impregnated in the whitesurface of the trap. The adult mortality was regis-tered weekly for I month. The results were ana-lyzed with an analysis of variance and significantdifferences among concentrations and time postim-pregnation were found (P > 0.05).

Entomological risks associated with waterwastetreatment plants

M. M. Rios, V. A. Rodrfguez, K. M. Valdez,C. A. Hern6ndez and L. Rosales

Laboratorio de Entomologta, Facultad deCiencias Biologicas, UANL, San Nicolas de los


Risk factors are all circumstances that affect hu-man health. In this study, our objective was to iden-tify the insects inside and outside of a wastewatertreatment plant that could cause a public healthproblem. Every week, samples were taken insideand outside of the Agua Industrial Monterrey S. deU. facility. Samples were taken with an entomolog-ical net in the general vegetation, and samples weretaken directly from the water. Insects were pre-served in ethyl alcohol and later identified. Fiveinsect orders were collected, which included 16families, 15 genera, and 16 species. Of these in-sects, only Chironomus plumosus is likely to be-come a public health problem, because its swarmscan cause panic among the public.

Coconut and yucca agars to produce Bacillusthuringiensis var. israelensis

J. Merello, P Ventosilla, J. Chauca, H. Guerra,B. Infante and E. P€rez

Instituto de Medicina Tropical Alexander vonHumboldt, and Universidad Peruana Cayetano

Heredia, Lima, Perfi

The entomopathogen Bacillus thuringiensis var.israelensis (Btr) is produced commercially usingexpensive, complex chemical fermentation media.We produced Bri using coconuts (Coco nucifera)and yucca (Manihot esculenta). To 100 ml of rawcoconut water and yucca infusion (15 g yucca,peeled, chopped, boiled 2 min in 150 ml of water,then filtered), we added 0.18 g of agar and thenautoclaved and poured the mixture into Petri dishes.Bacillus thuringiensis var. israelensis (strain IPS-82) was plated and incubated for 96 h at 30'C. Thebacteria were harvested, washed by centrifugation,and inactivated (75'C, 15 min). The coconut wateragar yielded 8O-85Vo sporulation, 3.49 x 106spores/ml, and a median lethal concentration (LCso): 2.41 X ICF spores/ml; yucca infusion agar yield-

DpcBrr.rnBn 20O0 Svuposruv oN Moseurro CoNrnol IN LATIN Auentcl 309

ed87-9OVo sporulation, l.l8 x lff spores/ml, andLCro : 2.66 x l0 spores/ml. Dr. de Barjac's stan-dard medium yielded 85-9O7o sporulation, lffspores/ml, and LCrn : l0 spores/ml. For bioassays,we used field-collected, 3rd-stage Anopheles pseu-dopunctipennis larvae. The LC.os showed no sig-nificant difference between the 3 media. P :

0.6342. Tfiptose phosphate broth and nutrient yeastsupplemented mineral agar media take longer (120h) to produce spores. Coconut and yucca agars areappropriate alternatives for local production of 8rl'.This work was funded bv Rivers of the World.

Population fluctuations of the malaria vectorAnopheles darlingi in southern Venezuela

Yasmfn Rubio-Palfs, Magda Magris, Ram6n Pazand Jo Lines

Escuela de Malariologia y SaneamientoAmbiental "Dr. Arnoldo Gabaldon," Maracay,

VeneTuela; CAICET, Puerto Ayacucho,VeneTuela; and London School of Hygiene andTropical Medicine, Inndon, United Kingdom

Malaria is one of the major causes of morbidityamong the Yanomami Amerindian population insouthern Venezuela. Traditional vector control withresidual indoor spraying of insecticides and outdoorspace spraying have failed due to several factors.These include the geographic situation, with diffi-cult access; sociocultural characteristics ofthe Yan-omami population, with frequent migrations andhousing with incomplete or no walls; circulation ofPlasmodium falciparum strains with multiple drugresistance; and biting behavior of the incriminatedvector Anopheles darlingi. To evaluate the impacton the vector population of an intervention involv-ing insecticide-treated bed-nets, monthly mosquitocollections were made beginning in June 1998 in18 villages located along the Orinoco, Mavaca, andOcamo rivers in the Upper Orinoco, AmazonasState, Venezuela. Mosquitoes were collected withCenters for Disease Control light traps set fiom1800 to 0600 h within selected dwellings in eachof the 18 villages for 4 nights per month everymonth. In the morning, mosquitoes were taken tothe field base in Ocamo, identified, and counted.Mosquitoes were kept dry on silica gel for futuresporozoite detection using enzyme-linked immu-nosorbent assay. In December 1998, bed-nets treat-ed with l0 g/m'� of lambdacyhalothrin were disrrib-uted to the entire population in 9 villages, whereasthe population of the remaining 9 villages were pro-vided with placebo-treated bed-nets. More than250,000 anophelines belonging to 4 species (An.darlingi, An. oswaldoi, An. strodei, and, An. trian-nulatus) were captured. Anopheles darlingi ac-counted for 99.8Vo of the mosquitoes identified.The number of mosquitoes caught per trap variedfrom 12 to 5,970 among villages. The village with

consistently higher mosquito densities was Ishin-otheri, located on the Ocamo River. Preliminary re-sults showed seasonal fluctuations in the abundanceof An. darlingi in all villages, with a major peakduring May 1999. Anopheline fluctuations werestrongly correlated with rainfall and river level (P< 0.05), whereas the effect of insecticide-treatednets on mosquito densities was not clear and morestudies are required.

Toxicity and sublethal effects of Bacillusthuringiensis var. israelensis (Vectobac G@) on

Aedes aegypti

G. Ponce, A. E. Flores, M. H. Badii,M. L. Rodriguez and I. Ferndndez

Department of Invertebrate hology andInboratory of Medical Entomology, and Facultyof Biological Sciences, University of Nuevo Le6n,San Nicokis de los Garza, Nuevo Le6n, Mdxico

Bacillus thuringiensis var. israelensis is highlytoxic to mosquito larvae. The objective of this re-search was to determine toxicity of Vectobac@ to2nd and 3rd instars of Ae. aegypti and the sublethaleffect of Vectobac on biological parameters ofadults under laboratory conditions. On the basis of24-h bioassays, the results indicated 0.0094,0.0168, and 0.0302 ppm for the 3OVo lethal con-centration (LC), median LC, and TOVo LC, respec-tively. The biological parameters such as growthrate, survival capacity, and reproductive potentialof this species under toxic effect of this pathogenicbacteria were detennined and compared with theuntreated control. The implications of these find-ings and their bearing on fleld-population dynamicsof Ae. aegypri are discussed.

Ecofogical aspects of Anophelcs spp. productionin excavations of abandoned mines in Matup6and Peixoto de Azevedo/Mato Grosso. Brazil

A. L. M. Ribeiro, R. H. Zimmerman andR. Dijunko Miyazaki

Mato Grosso/Brazil's Federal University, MatoGrosso, Brazil

We studied ponds created by abandoned mines,where anophelines are produced. Seventy-four ex-cavations were classified according to year sinceabandonment (2-4.O, 4.1-6.0, 6.1-8.0, 8.1-10.0,and more than 10.1 years). We studied the distanceto the city, vegetation, and limnological features ofthe ponds. After rainy periods, 87.87o of the exca-vations were positive for anopheline larvae andduring droughts, 86.7Vo were positive. Seven spe-cies of Anopheles were identified. They wereAnopheles albitarsis (s.1.), An. darlingi group, An.galvaoi, An. nuneztovari, An. strodei, An. triannu-latus (s.1.), and An. evansae. Anopheles albitarsis

3 1 0 JounNnr- oF THE AMERTcIN Moseuruo CoNrnol AssocrarroN Vol. 16. No. 4

occurred both near and distant from cities; An. dar-lingi was found only 8 km from the city. Of pondswith mosquitoes, 84Vo contained emergent plants.The length of time of abandonment of the minesdid not influence the distribution of anopheline spe-cies.

Laboratory studies of plant extracts forcontrolling Aedes aegypti

Julian Garcia-Rej6n, Juan Chable-Santos, Jos6Farf6n-A16, Luis Flores-Flores and Maria Alba

Loroflo

Laboratorio de Arbovirologia, Centro deInvestigaciones Regionales "Dr. Hideyo

No guc hi, " Universidad Auton6ma Yucatdn,M€rida, Yucatdn, Mdxico

In this study, we evaluated the extracts of plantsfrom Yucat6n State, M6xico, that could be used forthe control of the mosquito Aedes aegypti, the mainvector of dengue in Yucatdn. The extracts were ob-tained from the mature leaves of 16 plant species,mainly ornamental varieties. The leaves were driedat 90'C in an oven and were allowed to cool toambient temperature. Dry leaves (25 g) were addedto 5OO ml of water. This mixture was heated andthen boiled for 3 min, and then allowed to cool for24 h and filtered with cloth. The resulting infusionwas used in the toxicity tests. For the tests, 1 ml ofeach infusion was added to 100 rnl of water, towhich were added 25 4th-stage Ae. aegypti larvaeproduced at the Centro de Investigaciones of theUniversity of Yucatan. At 24 arrd 48 h postappli-cation, percent mortality was determined by count-ing larvae with abnormal movements versus normallarvae. Three repetitions were made for each treat-ment and respective control. Two of the 16 speciestested demonstrated a larvacidal effect; lady of thenight (Cestrum nocturnum) and the bougainvillea(Bougainvillea buttiana), with 100 and 2OVo mor-tality at 24 h, respectively. Untreated larvae had nomortality. These preliminary results indicate thatplants exist that currently only are used as orna-mentals that potentially could be used as biologicalinsecticides in M6xico. More plant species are be-ing tested and the close response of the 2 plantsmentioned is being studied.

Population genetics of Anopheles albimanus inLatin America using genetic markers: randomamplified polymorphic DNA-polymerase chain

reaction and mitochondrial DNA

Ana Maria P de M6rida. Alvaro Molina C..Eduviges Molina de Archila, Yadira Rangel and

W. C. Black IV

Universidad del Valle de Guatemala, GuatemolaCity, Guatemnla; Instituto de Zoologia Tropical,

Universidad Central de Venezuela, Caracas,Veneluela; and Department of Microbiology,Colorado State University, Fort Collins, CO

Anopheles albimanus is a species with a widegeographic range and an extremely variable phe-notype. Differing behavior, biologies, and vectorialstatus of many isomorphic Anopheles spp. make itessential to evaluate not only the seasonal popula-tion structure but also the spatial one, within thesame geographic region. Little is known about mo-lecular genetics, population structure and dynamics,barriers to gene flow, and phylogeny. Previousstudies in Guatemala and a few other Central andSouth American countries, showed populationswithin <200 km of one another were panmictic.However, at distances >200 km F statistic and geo-graphic distances were correlated, suggesting thatpopulations are isolated by distance. In this sense,a study of this species in 10 Latin Americnn coun-tries is proposed, the main objective being to yieldinformation covering these topics. The DNA wasextracted by the cetyltrimethylammonium bromidemethod and the mitochondrial DNA (mtDNA)(ND5) region was amplified by polymerase chainreaction (PCR) by using primers M2 and Pl. Sin-gle-strand conformation polymorphisms analysiswas done on the PCR products. After revealing thedifferent haplotypes found in each country, mostcommon ones will be selected and sequenced. Se-quences will be aligned in both directions (SE-

QUAID program) to correct the sequences. Parsi-mony, distance, and maximum likelihood analysis(Phylip and PAUP programs) will be performed.The l4GS06 random amplified polymorphic DNA-PCR and mtDNA markers indicate that Aedes ae-gypti populations along the northeastern coast ofMexico are isolated by distance.

Random amplified polymorphic DNA-polymerase chain reaction and mitochondrial

DNA markers indicate Aedes aegyptipopulations along the northeastern coast of

Mexico are isolated by distance

Norma Gorrochotegui-Escalante, M. L. Mufloz,Ildefonso Fernandez-Salas, B. J. Beaty and

W. C. Black IV

Centro de Investigaciones y Estudios Avanz,Instituto Politacnico NacionaL Mexico City,

Mdxico; Depamnent of Entomology, University ofCalifurnia, Riverside, CA: MEL, UANL, San

Nicokis de los Garza, Nuevo Le6n, Mixico: andDepartment of Microbiology, Colorado State

University, Fort Collins, CO

A population genetic analysis of gene flow wasconducted among IO Aedes aegypti populationsalong the northeastern coast of Mexico. Approxi-

DeceraeEn 2000 Syuposrurra oN Moseurro CoNrnol rN LerrN Avenrca 3 l l

mately 58 mosquitoes were sampled in each col-lection site from 7 cities. Four collections weremade from Monterrey to examine local patterns ofgene flow. Markers included 60 random amplifiedpolymorphic DNA (RAPD) loci amplified by thepolymerase chain reaction (PCR) single-strand con-formation polymorphism (SSCP) analysis of vari-ation in a 387-base pair region of the reduced nic-otinamide adenine dinucleotide dehydrogenasesubunit 4 (ND4) from the mitochondrial DNA(mtDNA). Seven mitochondrial haplotypes weredetected and phylogenetic analysis ofthe sequencesidentified 2 well-supported clades. Regression anal-ysis of geographic distances and pairwise F statis-tics estimated from RAPD markers indicated thatpopulations are isolated by distance and suggestedfree gene flow among collections within 9O-250km. However, isolation by distance was not detect-ed in a similar analysis of mtDNA haplotypes. Acollection from Nuevo Laredo had a unique patternof RAPD and mitochondrial haplotype frequenciesand reduced heterozygosity, suggesting that theNuevo Laredo population was probably founded byvery few mosquitoes.

Enzyme polymorphism among Triatomalongipennis from the west coast of Mexico:

baseline data

Josd Alejandro Martinez-Ibarra, Nina MalenaB arcenas-L6pez, B enj am(n Nogueda-Torres, Mario

Henry Rodriguez-L6pez and Porfirio Ramirez-Vallejo

Iaboratory of Genetic Markers, Colegio dePostgraduados, Texcoco, Mdxico; Parasitology

Laboratory, National School of BiologicalScience, Ayala, M€xico; Centro de Investigacionesde Enfe rme dade s I nfe c c i o s a s, I N S P, C ue rnav ac a,

Mixico

Allozyme variability in populations of the Cha-gas' disease vector Tiatoma longipennis was in-vestigated by means of starch gel electrophoresis.Samples were taken from 7 localities across therange of this insect on the west coast of Mexicowhere the insect is the prime vector. Zymogramsfor proteins coded by a total of 7 loci on 5 enzymes(esterases [ES EC 3.1.1.1.], catalase [CAT ECl-I 1.1.61, malate dehydrogenase IMDH EC 1.1. 1.37],malic enzyme [ME EC 1.1.1.40], and phosphoglu-coisomerase [PGI EC 5.L2.9)), were obtained. Allpopulations were highly polymorphic for these en-zymes, and also had some unique alleles. Allelefrequencies, proportion of polymorphic loci (P),mean heterozygosity per locus (H), and gene flowamong populations will be estimated.

Phylogenetic tree based on genetic distance:testing congruences in Albimanus Section

Hermes Piflango and Yadira Rangel

Instituto de Zoologia Tropical, Laboratorio deGendtica de Poblaciones y Vectores, Universidad

Central d.e Venezuela, Caracas, Venezuela

Congruence of trees from morphologic and mo-lecular data is a theme in many recent systematicpapers. However, the congruence between isozymeand morphologic or molecular trees has been un-deremphasized. The underlying notion is that any 2data sets from a single population sample must beconsistent, regardless of the apparently discordanttopologies of the trees. To perform a preliminaryevaluation of this issue, we used data of allele fre-quency obtained by protein electrophoresis of4 Ve-nezuelan species belonging to the Albimarnas Sec-tion of Anopheles (Nyssorhynchus) and from aspecies belonging to the sister section (Albitarsis).Such data were analyzed from the standpoint ofpopulation genetics and phylogenetic framework,and contrasted with the prevailing classification forthe section. We found partial correspondence bothfrom population genetic and phylogenetic analyses.However, we must use the complete array of bio-chemical and molecular characteristics of species toestablish phylogeny.

Infestation rates for the triatomines in the westcoast of Mexico

J. A. Martinez-lbar'ra, R. Alejandre-Aguilar,N. M. B6rcenas-Ortega, B. Nogueda-Torres,

E. Magall6n-Gast6lum andL. M. Rodrfguez-S6nchez

Colegio de Postgraduados, IFIT, Mixico-Texcoco, Texcoco, Mdxico; Laboratorio de

Parasitologia, E NCB/IPN Mar Carpio y Plan deAyala, Mdxico, Distrito Federal: and Centro

Universitaio de Ciencias de la Salud,Universidad de Guadalajara, Jalisco, Mdxico

Chagas' disease is a serious public health prob-lem in most American countries. In Mexico, littleis known about this triatomineborne disease and therisk of Trypanosoma cruzi infection for humanpopulations. Few studies have been conducted onentomological indicators recommended by the PanAmerican Health Organization and World HealthOrganization for evaluating human risk. Our teamfound 3 Triatoma species in Jalisco statei T. lon-gipennis (3 localities), T. picturata (1 locality), andT. pallidipennis (1 locality). Only T. longipennishad 2 indicators suggesting risk for humans: colo-nization indicator (41.lVo,5 of 12 houses), and nat-ural infestation (19.6Vo, 28 ot 143 triatomines). InNayarit, indicators for only 2 species were found:T. longipennis colonization was 5O-10OVo and nat-

) t L JounNnl oF THE AMERrcnr Moseurro CoNrnol Assocrnrror Vor-. 16, No. 4

ural infestation was 19.6-1007o, whereas for T. pic-turata, colonization was 10O7o in all the localitiesand natural infestation was 19.6-1OOVo. Accordingto analysis of these data, human populations in bothstudy areas are at risk of being infected with 7.cruzi by the triatomines.

Resting site selection in Triatoma gerstaeckeridetermined by its physiologic stages

J. L. Torres-Estrada, J. A. Martinez-Ibarra,J. A. Garcfa-P€rez and E Santillin-Valenzuela

Centro de Investigaci6n de Paludismo, INSP/SSA,Tapachula, Chiapas, Mdxico; Colegio de

Post graduados, I F IT, Mixico-Texcoco, Texcoco,Mdxico; and Facultad de Ciencias Biol6gicas,UANL San Nicolds de los Garza, Nuevo Le6n,

M6xico

Few studies have been conducted in Mexico ontriatomine behavior. Triatoma gerstaeckeri is oneof the most dangerous vectors of Trypanosoma cru-zi in northeast Mexico. The influence of combina-tions of 2 different physiologic stages in the selec-tion of resting sites on adults of T. gerstaeckeri wasstudied. An 8-m3 light-proof cage was built usingglass and steel. Three simulated indoor walls werebuilt of concrete block, cardboard, or ditched reedgrass (1 of each) and 2 simulated mouse shelterswere added, 1 with a mouse inside and the otherempty. Four groups of 10 adult triatomines, eachwith a combination of fed or fasted and fecund orunfecund stage were released in the center of thecage, I by l. A typical rural house was used for asimilar field experiment. Under laboratory condi-tions, most fed triatomines preferred climbing theconcrete block wall as a resting site, whereas mostfasted bugs preferred climbing the cardboard wall,all of them independently of their stage of fecun-

dity. Under field conditions, most triatomines pre-ferred to stay on the ground without climbing anysurrounding wall, independently of their stage offecundity. Results from these field experimentswere consistent with previous experiences in flnd-ing triatomines under natural conditions.

REFERENCES CITED

Clark GG (organizer). 1995. Mosquito vector control andbiology in Latin America-a fifth symposium. J AmMosq Control Assoc 11:343-353.

Clark GG (organizer). 1996. Mosquito vector control andbiology in Latin America-a sixth symposium. J AmMosq Control Assoc 12:46O-471.

Clark GG, Rangel YN (organizers). 1997. Mosquito vec-tor control and biology in Latin America-a seventhsymposium. J Am Mosq Control Assoc 13:113-126.

Clark GG, Rangel YN (organizers). 1998. Mosquito vec-tor control and biology in Latin America-an eighthsymposium. J Am Mosq Control Assoc 14:219*233.

Clark GG, Rangel YN (organizers). 1999. Mosquito vec-tor conffol and biology in Latin America-a ninth sym-posium. J Am Mosq Control Assoc 15:.4O7-421.

Clark GG, Suarez MF (organizers). 1991 . Mosquito vectorcontrol and biology in Latin {rnslisa-n symposium. JAm Mosq Control Assoc 7:633-645.

Clark GG, Suarez MF (organizers). 1992. Mosquito vectorcontrol and biology in Latin America-a second sym-posium. J Am Mosq Control Assoc 8:305-317.

Clark GG, Suarez MF (organizers). 1993. Mosquito vectorcontrol and biology in Latin America-a third sympo-sium. J Am Mosq Control Assoc 9'.441-453.

Gertsch WJ, Soleglad M. 1972. Studies in North Ameri-can scorpions of the genera Uroctonus and Vejovis(Scorpionida, Vejovidae). Am Mus Nat Hist 148:551-607.

Hoffman C. 1932. Los Scorpiones de Mixico. I" parte:Chactidae, Diplocentridae y Vejovidae. Ann Inst Biol2:29t-408.

Stockwell SA. 1992. Systematic observations on NorthAmerican Scorpionida with a key and checklist of thefamilies and genera. J Med Entomol 29:407-422.

MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATIN ...

Documents

Transcript of MOSQUITO VECTOR CONTROL AND BIOLOGY IN LATIN ...