Equine West Nile Encephalitis, United States

Abstract

After the 1999 outbreak of West Nile (WN) encephalitis in New York horses, a case definition was developed that specified the clinical signs, coupled with laboratory test results, required to classify cases of WN encephalitis in equines as either probable or confirmed. In 2000, 60 horses from seven states met the criteria for a confirmed case. The cumulative experience from clinical observations and diagnostic testing during the 1999 and 2000 outbreaks of WN encephalitis in horses will contribute to further refinement of diagnostic criteria.

Incidence and effects of West Nile virus infection in vaccinated and unvaccinated horses in California

“…These sampling dates were chosen for the vaccinated horses because they coincided with the predicted beginning and end of the WNV transmission season in 2005. Sera collected from the unvaccinated horses were also evaluated for the presence of neutralizing antibodies to WNV by plaque reduction neutralization test (PRNT) at the National Veterinary Services Laboratory (Ames, Iowa, USA) [3,20]. The IgM capture ELISA [23] performed at the California Animal Health and Food Safety Laboratory was used to confirm WNV infection in horses that exhibited signs consistent with WND [15,20].…”

“…In 1999, WNV was first detected in North America in New York, and subsequently the virus spread throughout Canada, the USA, Mexico and the Caribbean [13,14,21]. Horses have been the mammalian species most impacted during the current epidemic of WNV infection in North America, with attendant high morbidity and mortality [20,22,[25][26][27][28]. WNV was not detected in California until July 2003, when the virus was identified in Culex tarsalis mosquitoes in the Imperial Valley of southeastern California [24].…”

Antibody Responses Induced by Experimental West Nile Virus Infection with or without Previous Immunization with Inactivated Japanese Encephalitis Vaccine in Horses

“…Furthermore, abnormal behavior, dysmetria, teeth grinding, facial nerve paralysis and dysphagia have been observed as a result of brain damage due to WNV infection [3,25]. Cases of equine infection have been reported during epidemics, or outbreaks, of WNV in many countries, including Italy [1], France [16], Canada [26] and the United States [17], and thus WNV infection has become a major concern of the horse industry.…”

West Nile Virus: Characteristics of an African Virus Adapting to the Third Millennium World

“…In addition, together with an automated RNA extraction, real-time RT-PCR can be used in large-scale surveillance, and allows quantitative measurement of viral nucleic acids [42]. In several studies, molecular detection assays based on broadly reactive (degenerate) primers may be used for the simultaneous detection and quantification of distinct flaviviruses using species-specific and group-specific primers in a single reaction [40] or targeting the flavivirus consensus amplimers located at the RNA-dependent RNA polymerase domain of the NS5 protein [43].…”