Order Strongylida HookwormsHookworms –Necator americanus Americas, Africa, AsiaAmericas, Africa,...

Order Strongylida Order Strongylida • HookwormsHookworms– Necator americanusNecator americanus• Americas, Africa, AsiaAmericas, Africa, Asia

– Ancylostoma duodenaleAncylostoma duodenale• Europe, Northern Africa, Asia, Europe, Northern Africa, Asia,

AmericasAmericas

– Ancylostoma braziliensisAncylostoma braziliensis• Carnivores in the tropicsCarnivores in the tropics• Cutaneous larval Cutaneous larval

migrans/creeping eruptionmigrans/creeping eruption– Ancylostoma caninumAncylostoma caninum• CanidsCanids• Cutaneous larval Cutaneous larval

migrans/creeping eruptionmigrans/creeping eruption

•Free-living Juveniles

•Filariform are infective

Rhabditiform and Filariform JRhabditiform and Filariform J33’s’s

•Filariform are infective

Necator americanus Ancylostoma duodenaleNecator americanus Ancylostoma duodenale

TransmissionTransmission

• Ancylostoma duodenaleAncylostoma duodenale– CutaneousCutaneous– Oral ingestion of juvenilesOral ingestion of juveniles– Paratenic hostsParatenic hosts– TransmammaryTransmammary– Transplacental?Transplacental?

• Necator americanusNecator americanus– CutaneousCutaneous

Hookworm DiseaseHookworm Disease

• 1300 million people infected1300 million people infected

• 160 million experience illness160 million experience illness

• Severity depends on:Severity depends on:1.1. Number of wormsNumber of worms

2.2. Species infected withSpecies infected with

3.3. Nutritional status of hostNutritional status of host

Hookworm DiseaseHookworm Disease

• Necator americanusNecator americanus< 25 no symptoms< 25 no symptoms

25-100 light symptoms25-100 light symptoms

100-500 moderate symptoms100-500 moderate symptoms

500-1000 severe symptoms500-1000 severe symptoms

> 1000 Very severe, often fatal> 1000 Very severe, often fatal

• Ancylostoma duodenaleAncylostoma duodenale100+ severe symptoms100+ severe symptoms

PathogenesisPathogenesis

1.1. Cutaneous PhaseCutaneous Phase• Juveniles enter skinJuveniles enter skin• Entrance into blood vessels initiates tissue Entrance into blood vessels initiates tissue

reaction that can kill juvenilesreaction that can kill juveniles• Itching/rash at location of penetrationItching/rash at location of penetration• Caused by bacteriaCaused by bacteria

• ““Ground itch”Ground itch”


2. Pulmonary Phase2. Pulmonary Phase• Juveniles enter alveoli and move up bronchi Juveniles enter alveoli and move up bronchi

to throatto throat• Usually asymptomaticUsually asymptomatic• HemorrhagingHemorrhaging• Dry coughDry cough


3. Intestinal Phase3. Intestinal Phase• Adults enter intestineAdults enter intestine• Attach to mucosa with teethAttach to mucosa with teeth• Feed on bloodFeed on blood

Adults pull in a plug of tissue and suck Adults pull in a plug of tissue and suck blood! blood!


• Blood loss extensiveBlood loss extensive– LesionsLesions– AnticoagulantsAnticoagulants

• Blood loss exceeds what worms ingestBlood loss exceeds what worms ingest– Necator americanusNecator americanus • 0.03 ml/worm/day0.03 ml/worm/day

– Ancylostoma duodenaleAncylostoma duodenale • 0.15-0.26 ml/worm/day0.15-0.26 ml/worm/day

Small Intestine Infected with Small Intestine Infected with Hookworms: They are sloppy feeders!Hookworms: They are sloppy feeders!


• Heavy infectionsHeavy infections– Anemia (Iron Deficiency Anemia)Anemia (Iron Deficiency Anemia)– Severe protein deficiencySevere protein deficiency– EdemaEdema– StuntingStunting– Mental dullnessMental dullness– Heart failureHeart failure

Hookworm disease: statue (A) and child (B) from Costa Rica Hookworm disease: statue (A) and child (B) from Costa Rica with typical stance caused by malnutrition and severe with typical stance caused by malnutrition and severe

hookworm infection. (Courtesy of Dr. Herman Zaiman and hookworm infection. (Courtesy of Dr. Herman Zaiman and Muriel Jones). Muriel Jones).

Iron Deficiency AnemiaIron Deficiency Anemia

• Decrease in erythrocyte count due to lack of Decrease in erythrocyte count due to lack of ironiron

• Less oxygen gets to tissuesLess oxygen gets to tissues

• 2 billion people2 billion people

Iron Deficiency AnemiaIron Deficiency Anemia

• Affects:Affects:

• Protein-energy malnutrition Protein-energy malnutrition

– Growth and development of childrenGrowth and development of children• PhysicalPhysical• CognitiveCognitive

– PregnancyPregnancy• Risk of death of mother and childRisk of death of mother and child• Low birth weightLow birth weight• Premature birthPremature birth

– General healthGeneral health• Loss of energyLoss of energy• WeaknessWeakness• Shortness of breathShortness of breath• Mental dullnessMental dullness

• ““The disease induced by the hookworm…The disease induced by the hookworm…was never suspected to be a disease at all. was never suspected to be a disease at all. The people who had it were merely The people who had it were merely supposed to be lazy, and were therefore supposed to be lazy, and were therefore despised and made fun of, when they should despised and made fun of, when they should have been pitied.”have been pitied.”

- Mark Twain (Letters from the Earth)- Mark Twain (Letters from the Earth)

DiagnosisDiagnosis

• Demonstration of eggs in fecal smearDemonstration of eggs in fecal smear• Cannot distinguish species by eggsCannot distinguish species by eggs

Melenic diarrhea!

Frank blood in diarrhea!

TreatmentTreatment

• MebendazoleMebendazole

• Single dose effectiveSingle dose effective

• Iron supplementationIron supplementation

• Drug resistance of Drug resistance of N. N. americanusamericanus in Africa in Africa

EpidemiologyEpidemiology

• How do you get infected?How do you get infected?• Necator americanusNecator americanus– Juveniles penetrate skinJuveniles penetrate skin

• Ancylostoma duodenaleAncylostoma duodenale– Juveniles penetrate skinJuveniles penetrate skin– Ingest juveniles orallyIngest juveniles orally– Paratenic hostParatenic host– TransmammaryTransmammary– TransplacentalTransplacental


• TransmissionTransmission• Environmental conditionsEnvironmental conditions– NeedNeed

• MoistureMoisture• Warm temperatureWarm temperature• ShadeShade

– Juveniles live in moisture in the soilJuveniles live in moisture in the soil• Migrate to stay in optimal conditionsMigrate to stay in optimal conditions• Dry: Move downwardDry: Move downward• Wet: Move upward to surface of soil extend upward “looking Wet: Move upward to surface of soil extend upward “looking

for a host”for a host”

– Live 3 weeksLive 3 weeks


• Common in tropical or subtropical areasCommon in tropical or subtropical areas

• i.e. Southeastern U.S.i.e. Southeastern U.S.

Robert, LARobert, LA

Transmission “Hot spots”Transmission “Hot spots”

• MinesMines

• Coffee, banana, sugarcane plantationsCoffee, banana, sugarcane plantations

Other Hookworm SpeciesOther Hookworm Species

• Ancylostoma braziliensisAncylostoma braziliensis– Domestic and wild carnivores in tropicsDomestic and wild carnivores in tropics– Most common cause of Most common cause of cutaneous larval cutaneous larval

migrans/creeping eruption in humansmigrans/creeping eruption in humans

• Ancylostoma caninumAncylostoma caninum– Adults occur in canids (infrequently humans)Adults occur in canids (infrequently humans)– cutaneous larval migrans/creeping eruption in cutaneous larval migrans/creeping eruption in

humanshumans

Ancylostoma caninumAncylostoma caninum

Cutaneous Larval Migrans/ Creeping Cutaneous Larval Migrans/ Creeping EruptionEruption

• Juveniles penetrate skinJuveniles penetrate skin

• Cannot complete Cannot complete migrationmigration

• Tunnel through skinTunnel through skin

• Secondary infectionSecondary infection

• Weeks-monthsWeeks-months

Cutaneous Larval Migrans/ Creeping Cutaneous Larval Migrans/ Creeping EruptionEruption

• ““Soil born” nematodes or “Geohelminths”Soil born” nematodes or “Geohelminths”

– Ascaris Ascaris sp.sp.

– Trichuris trichiuraTrichuris trichiura

– Necator americanus Necator americanus

– Ancylostoma duodenaleAncylostoma duodenale

Soil Born NematodesSoil Born Nematodes

““Soil-born” NematodesSoil-born” Nematodes

• Development to infective stageDevelopment to infective stage• AscarisAscaris sp. sp.– Eggs embryonate in soilEggs embryonate in soil

• Trichuris trichiuraTrichuris trichiura– Eggs embryonate in soilEggs embryonate in soil

• Necator americanusNecator americanus– Eggs embryonate in soilEggs embryonate in soil– Juveniles develop in soilJuveniles develop in soil

• Ancylostoma duodenaleAncylostoma duodenale– Eggs embryonate in soilEggs embryonate in soil– Juveniles develop in soilJuveniles develop in soil

Epidemiological Model of Soil-Born NematodesEpidemiological Model of Soil-Born Nematodes

SoilInfected people

Uninfected people

Development to infective

stage

2. Contact1. Contact

1. Eggs released with feces of infected human. Eggs develop in the environment, commonly in soil. Development to the infective stage must occur for successful transmission.

2. Human contacts infective stage. How does this contact differ among species discussed?

Sensitivity to Environmental ConditionsSensitivity to Environmental Conditions

• Rank the species according to their Rank the species according to their sensitivitysensitivity

1.1. AscarisAscaris sp. sp.

2.2. Trichuris trichiuraTrichuris trichiura

3.3. Hookworm speciesHookworm species

• How is sensitivity going to effect their How is sensitivity going to effect their distribution?distribution?

DistributionDistribution

Ascaris sp.

Trichuris

Hookworms

Warm moist habitat

DistributionDistribution

Ascaris sp.

Trichuris

Hookworms

Warm moist habitat

Southeastern United States

Okefenokee Swamp, GAOkefenokee Swamp, GA

• Warm temperaturesWarm temperatures

• High RainfallHigh Rainfall– MoistureMoisture– Runoff Runoff

• Dense vegetationDense vegetation– ShadeShade

• High humidityHigh humidity

OuthousesOuthouses

Socioeconomic statusSocioeconomic status

• PovertyPoverty

• AttitudeAttitude

Scotlandville, LAScotlandville, LA

• Parasite survey of school children 1974Parasite survey of school children 1974– 27% 27% Ascaris lumbricoidesAscaris lumbricoides– 22% 22% Trichuris trichiuraTrichuris trichiura– 4% Hookworms4% Hookworms

• Which families are infected with parasites?Which families are infected with parasites?

• Is poverty correlated with infection in Is poverty correlated with infection in Scotlandville?Scotlandville?

• What is the cause and effect relationship?What is the cause and effect relationship?

ParasitismParasitism

PovertyPoverty

• Poor facilitiesPoor facilities

• Lack of clean Lack of clean waterwater

• Food qualityFood quality

• Sick peopleSick people

• Economic lossEconomic loss

•TreatmentTreatment

•Lost days of Lost days of workwork

•Reduced Reduced cognitive cognitive abilitiesabilities

SummarySummary

• Different way of lifeDifferent way of life• Climate Climate – TemperatureTemperature– WaterWater– VegetationVegetation

• PovertyPoverty– Correlates with parasitismCorrelates with parasitism– Sewage disposalSewage disposal– Reflected in attitudeReflected in attitude

• Close to homeClose to home

GeophagyGeophagy

GeophagyGeophagy• Ingestion of soilIngestion of soil• Historical practiceHistorical practice• Modern practice in Africa and SE U.S.Modern practice in Africa and SE U.S.• Special types of soil are soldSpecial types of soil are sold– Clay based soilClay based soil

• Markets in Georgia, parts of Africa, and parts of Markets in Georgia, parts of Africa, and parts of South America sell soil for consumption.South America sell soil for consumption.

• Intense cravings for soilIntense cravings for soil– 55 yr old woman who would eat only soil if she could55 yr old woman who would eat only soil if she could

Why?Why?

• PregnancyPregnancy• Cure for ailmentsCure for ailments• Religious practiceReligious practice

• Clay soils contain kaolin, the principal ingredient in Clay soils contain kaolin, the principal ingredient in Kaopectate.Kaopectate.– Morning sicknessMorning sickness– Intestinal ailmentsIntestinal ailments

• Nutritional supplement Nutritional supplement – IronIron– MagnesiumMagnesium– CalciumCalcium– PhosphorusPhosphorus

GeophagyGeophagy

• Geophagy is often correlated withGeophagy is often correlated with– AnemiaAnemia– Parasite infectionParasite infection

• Cause and effect?Cause and effect?– Does anemia cause geophagy?Does anemia cause geophagy?– Does parasitic infection cause geophagy?Does parasitic infection cause geophagy?– Does geophagy cause anemia?Does geophagy cause anemia?– Does parasitic infection cause anemia?Does parasitic infection cause anemia?– Does geophagy cause parasitic infection?Does geophagy cause parasitic infection?

Geophagy and ParasitismGeophagy and Parasitism

• Western KenyaWestern Kenya

GeophagicGeophagic Non-geophagicNon-geophagic

Trichuris trichiuraTrichuris trichiuraPrevalence Prevalence Egg per gram (range)Egg per gram (range)

44%44%

48 (13-133)48 (13-133)

37%37%

20 (7-37)20 (7-37)

Ascaris lumbricoidesAscaris lumbricoidesPrevalence Prevalence Egg per gram (range)Egg per gram (range)

16%16%

2413 (1055-6903)2413 (1055-6903)

9%9%

455 (25-920)455 (25-920)

Geissler et al. 1998. Transactions of the Royal Society of Tropical Medicine and Hygiene 77: 432-438.

SummarySummary

• Geophagy is a relatively common practiceGeophagy is a relatively common practice

• Geophagy is associated with parasitismGeophagy is associated with parasitism– Geophagy causes parasitismGeophagy causes parasitism– Does parasitism cause geophagy?Does parasitism cause geophagy?

Questions?Questions?

• What are the species of “soil-born” What are the species of “soil-born” nematodes?nematodes?

• Why is Why is Enterobius vermicularisEnterobius vermicularis not a “soil- not a “soil-born” nematode?born” nematode?

Order Strongylida HookwormsHookworms –Necator americanus Americas, Africa, AsiaAmericas, Africa,...

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