Evaluating risk of introduction of WNV in Eastern Piedmont ...
Transcript of Evaluating risk of introduction of WNV in Eastern Piedmont ...
Vectors collected in these areas were tested and two of their species
resulted infected by WNV: Culex pipiens and Ochlerotatus caspius.
Throughout European Culex modestus is also considered potential bridge
vector from birds to mammals.
In this study we described the spatial distribution of WNV vectors located
in Northwestern Italy. This territory is close to WNV foci area and could be
the door of WNV entrance in Piedmont.
WNV Spread
Study Area
Introduction
West Nile Virus (WNV) is a reemerging
zoonoses in Italy. The first outbreak
occured in Tuscany in 1998, close to
wetland area. No other cases were
reported during next ten years, but virus
introduction continued. In Autumn 2008
new foci in human and horses were
detected in Emilia Romagna region and
WNV spread to neighbouring areas.
Mosquitoes collection
Cluster analysis
Evaluating risk of introduction of WNV in Eastern Piedmont, Northern Italy
Luigi Bertolotti , Donal Bisanzio , Francesco Cerutti , Andrea Mosca , Luca Balbo , Gonzalo M. Vazquez-Prokopec , Uriel Kitron , Mario Giacobini
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Remote sensing data
Corine of landuse 2001
Digital Terrain Model
MODIS 16 days NDVI
MODIS 8 days Land Surface
Temperature (LST)
(week) (week)
36 Mosquito CO Bited Traps, weekly collection from May to October,
2000-2006
29 Mosquito CO Bited Traps, weekly collection from May to October,
2007-2008
Traps were placed randomly and they are not clustered
Since 2000 control strategies against O. caspius were performed using spray
biological lavicidal, Bacillus thuringiensis var. israelensis (Bti)
Two types of control were performed: spraying all rice fields every year by
helicopter (TR1) or treating only high abundance spots (TR2)
Study area
Week
Generalized linear mixed model (GLMM)
Getis-Ord Gi(*d) was used to find local clusters
Analyses between traps were based on inverse of
their distances
C. pipiens showed several clusters in all years
C.modestus and O. caspius showed clusters in few
years
High abundance and several significant high spot of
adult mosquitoes was recorded in areas near rice
fields, north of study area.
Random effect:
Trap location
Months of year
Fixed effect:
NDVI
Weekly mean temperature
Weekly rainfall
DTM
Seasonality (sinusoidals function)
Different treatments
Spatial correlation function was implemented
Model was trained with 2000-2006 data
Validation was performed on 2007-2008 data
collection
Conclusion
1,439,059 mosquitoes of different species were
trapped in 47430 trap/nights (Tab. 1)
O. caspius, C. pipiens and C. modestus were the
most abundant species
O. caspius and C. pipiens showed peaks in late
summer
C. modestus did not show seasonality
A model was built for C. pipiens and O. caspius
It was difficult to make a model for C. modestus,
it have not link with variables studied
Presence of vectors confirms that study area could be a way for the spreading of WNV in Piedmont
Areas near rice fields have a high risk of future outbreak. In this part of territory there is the highest presence of vector, and it
is a good habitat for migratory birds
Model confirm that Bti control of O. caspius may be considered a good method to decrease its population
C. modestus did not show any seasonability and this species seems to be linked to agricultural activity
The model captures ecological features of different species and it could be used to plan surveillance
This study was funded by Lagrange Foundation: Donal Bisanzio. This study was funded by Regione Piemonte, Ricerca Sanitaria Finalizzata 2008 program: Luigi Bertolotti
Bibliography
Autorino, Gian Luca, Antonio Battisti, Vincent Deubel, Giancarlo Ferrari, Riccardo Forletta, Armando Giovannini, Rossella Lelli, Severine Murri, and Maria Teresa Scicluna. 2002. West Nile virus epidemic in horses, Tuscany
region, Italy. Emerg Infect Dis 8, no. 12: 1372-1378.
Calistri, P, a Giovannini, G Savini, F Monaco, L Bonfanti, C Ceolin, C Terregino, M Tamba, P Cordioli, and R Lelli. 2009. West Nile Virus Transmission in 2008 in North-Eastern Italy. Zoonoses and public health: 1-9
Gobbi, F, G Napoletano, C Piovesan, F Russo, A Angheben, A Rossanese, A M Cattelan, et al. 2009. Where is West Nile fever? Lessons learnt from recent human cases in northern Italy. Euro Surveill 14, no. 10.
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Bolker, B.M. et al., 2009. Generalized linear mixed models: a practical guide for ecology and evolution. Trends in ecology & evolution (Personal edition), 24(3), 127-35.
DTM
NDVILST
Corine Landuse 2001 Remote sensing images, regarding sample periods (2000-2008), were
collected
All data were processed to correct atmospheric disturbance
Collected data:
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Tab.1: Annual number of mosquitoes collected in the area
Correlograms on weekly collections from 2000-2008
Model detected area where high number of mosquitoes
were collected
Model fited better for C. pipiens than for O. caspius, due
to their different homerange
Department of Animal Production, Epidemiology and Ecology, Faculty of Veterinary Medicine, University of Torino, ItalyMBC - Molecular Biotechnology Center, University of Torino, ItalyDepartment of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, USAIPLA, Institute for wood plants and environment, Torino, ItalyDeptartment of Environmental Studies, Emory University, Atlanta, GA, USAFogarty International Center, National Institutes of Health. Bethesda, MD 20892, USA
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GLMM represent a class of fixed effects regression
models with an inclusion of random effects for several
types of dependent variables
Tab.2: Results of GLMM model for C. pipiens and O. caspius
WeekWeek
CO Bited Trap2