Impact of Climate and Environmental Factors on West Nile Virus Circulation in Iran.
BACKGROUND
Geographic distribution of West Nile virus (WNV) is heterogeneous in Iran by a high circulation in the southern-western areas. The objective of our study was to determine environmental and climatic factors associated with the risk of WNV equine seropositivity in Iran.


METHODS
Serological data were obtained from a serosurvey conducted in equine population in 260 districts in Iran. The climate and environmental parameters included in the models were distance to the nearest wetland area, type of stable, Normalized Difference Vegetation Index (NDVI), annual mean temperature, humidity and precipitation.


RESULTS
The important risk factors included annual mean temperature, distance to wetlands, local and seasonal NDVI differences. The effect of local NDVI differences in spring was particularly notable. This was a normalized difference of average NDVI between two areas: a 5 km radius area centered on the stable and the 5-10 km surrounding area.


CONCLUSIONS
The model indicated that local NDVI's contrast during spring is a major risk factor of the transmission of West-Nile virus in Iran. This so-called oasis effect consistent with the seasonal production of vegetation in spring, and is associated to the attractiveness of the local NDVI environment for WNV vectors and hosts.
Viral Vaccines Production Department, Pasteur Institute, Tehran, Iran; TIMC-IMAG Team EPSP, VetAgroSup, Campus Vétérinaire de Lyon, France.
Farzaneh
F
Ahmadnejad
Quarantine and Biosafety Directorate General, Iran Veterinary Organization, Tehran, Iran.
Vahid
V
Otarod
Department of Geography, Razi University, Kermanshah, Iran.
Amanollah
A
Fathnia
Faculty of Geography, Kharazmi University, Tehran, Iran.
Ali
A
Ahmadabadi
Department of Poultry Viral Diseases, Razi Vaccine and Serum Research Institute, Alborz, Iran.
Mohammad H
MH
Fallah
Viral Vaccines Production Department, Pasteur Institute, Tehran, Iran.
Alireza
A
Zavareh
Viral Vaccines Production Department, Pasteur Institute, Tehran, Iran.
Nargess
N
Miandehi
University Paris Est, Anses, Laboratory of Animal Health, Epidemiology Unit, Maisons-Alfort, France.
Benoit
B
Durand
TIMC-IMAG Team EPSP, VetAgroSup, Campus Vétérinaire de Lyon, France.
Philippe
P
Sabatier
Climate; Environment; NDVI; West Nile Virus; Wetland