Diptera: Culicidae , infected per os from a membrane feeder, transmitted West Nile virus family Flaviviridae, genus Flavivirus, WNV at 26 degrees C horizontally during feeding to hamsters and suckling mice and vertically to F1 progeny during egg deposition. No females deposited eggs infected with WNV after the first bloodmeal on d pi. Females vertically transmitted WNV during egg laying after their second, third, and fourth bloodmeals on days pi.
WNV acute flaccid paralysis is usually clinically and pathologically identical to poliovirus-associated poliomyelitis, with damage of anterior horn cells, and may progress to respiratory paralysis requiring mechanical ventilation. WNV poliomyelitis often presents as isolated limb paresis or paralysis and can occur without fever or apparent viral prodrome. Clinical Evaluation Routine clinical laboratory studies are generally nonspecific.
Outcomes Most patients with nonneuroinvasive WNV disease or WNV meningitis recover completely, but fatigue, malaise, and weakness can linger for weeks or months. Links with this icon indicate that you are leaving the CDC website. Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
You will be subject to the destination website's privacy policy when you follow the link. CDC is not responsible for Section compliance accessibility on other federal or private website. Cancel Continue. Vaccinate semi-annually or more frequently every 4 months , depending on risk. Annual revaccination is best completed in the spring, prior to the onset of peak insect vector season.
While neither of the licensed vaccines is labeled for administration to pregnant mares at this time, it is recommended that mares be ideally vaccinated before breeding when possible. However, practitioners have vaccinated thousands of pregnant mares due to the risk associated with pregnant mares getting the disease from infected mosquitoes.
It has been accepted practice by many veterinarians to administer vaccines to pregnant mares on the assumption that the risk of adverse consequences of WNV infection outweighs any reported adverse effects of use of vaccines in pregnant mares. Booster vaccination of pregnant mares 4 to 6 weeks before foaling provides augmented passive colostral protection to their foals, lasting for months. Primary vaccination of foals from vaccinated mares should be started at months of age in order to avoid interference from colostral antibodies.
Foals from non-vaccinated mares may be vaccinated earlier than three months of age as they may not have colostral interference issues; however, data on which to base more specific recommendations for foals from non-vaccinated mares is not sufficient at this time.
Foals should be revaccinated at 1 year of age in the Spring of the year following their birth to ensure adequate protection. Because of the high mortality associated with West Nile virus, it is recommended that foals born in areas where there is a high risk of exposure to West Nile virus should receive an initial series of three 3 doses of vaccine against West Nile beginning at 3 months of age and at 4- to 6- week intervals. The third dose may go at an interval of weeks if desired, followed by a fourth dose at 1 year of age.
Many veterinarians, in Southern states where mosquitoes are active year-round, prefer to vaccinate horses semiannually or more frequently to help ensure uniform protection throughout the year, although this practice is not specifically recommended by manufacturers of vaccines.
Effect of environmental temperature on the ability of Culex pipiens Diptera: Culicidae to transmit West Nile virus. J Med Entomol. PhD dissertation. University of Florida; Gainesville, FL: West Nile virus dissemination and tissue tropisms in orally infected Culex pipiens quinquefasciatus.
Vector-Borne Zoonotic Dis. Vector competence of California mosquitoes for West Nile virus. Emerg Infect Dis. West Nile virus, epizootiology in the southeastern United States, Intrinsic factors affecting vector competence of mosquitoes for arboviruses. Annu Rev Entomol. West Nile fever.
In: Monath TP, editor. The Arboviruses: epidemiology and ecology. Temperature, viral genetics, and the transmission of West Nile virus by Culex pipiens mosquitoes. PLoS Pathogens. Effect of temperature of extrinsic incubation on the vector competence of Culex tarsalis for western equine encephalomyelitis virus. Am J Trop Med Hyg. Rapid detection of West Nile virus from human clinical specimens, field collected mosquitoes, and avian samples by a TaqMan reverse transcriptase-PCR assay.
J Clin Microbiol. A newly emergent genotype of West Nile virus is transmitted earlier and more efficiently by Culex mosquitoes. Environmental and biological factors influence Culex pipiens quinquefasciatus Say Diptera: Culicidae vector competence for Saint Louis encephalitis virus.
Impact of extrinsic incubation temperature and virus exposure in vector competence of Culex pipiens quinquefasciatus Say Diptera: Culicidae for West Nile virus. West Nile virus infection rates in Culex nigripalpus do not reflect transmission rates in Florida.
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