Outcome of equids with clinical signs of West Nile virus infection and factors associated with death

Abstract

Among equids with WNV infection, age, vaccination status, an inability to rise, and sex were associated with the risk of death.

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

“…Although WND has been described in horses that were previously vaccinated with inactivated WNV vaccine [7,15,25,26] there was no evidence of disease in vaccinated horses including those that were seronegative to the virus at the beginning of the 2005 WNV season. Furthermore, several of these horses had evidence of infection during 2005 because they seroconverted to WNV between April and November.…”

“…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].…”

“…Furthermore, although several studies have noted that some horses vaccinated against WNV respond poorly and that WND can occur in vaccinated animals [2,10,15,25,26], there are no reliable estimates as to the frequency of this phenomenon. The objective of the study reported here was to compare the incidence and effects of natural WNV infection in unvaccinated and vaccinated horses in California.…”

West Nile virus: A re-emerging pathogen revisited

“…Illness usually last for 3 wk [194] . Even though outbreaks resulted in 25% to 45% of mortality rates among affected horses [194,195] , implementation of vaccination campaigns has strongly reduced these mortality rates [167] , and treatment guidelines for horses with WND have been published. Lesions by WNV infection in horses are mainly limited to the CNS such as polioencephalomielitis and, in the most severe cases, neuronal degeneration [159] .…”

Comparative Efficacies of Three Commercially Available Vaccines against West Nile Virus (WNV) in a Short-Duration Challenge Trial Involving an Equine WNV Encephalitis Model

“…This preparation also contains an adjuvant. Several epidemiological studies investigating the outbreaks throughout the United States have justified the use of these commercially available vaccines as a preventative strategy (6,8,21,23,30).…”