Outcome of equids with clinical signs of West Nile virus infection and factors associated with death.
OBJECTIVE
To determine outcome of equids in the western United States with clinical signs of West Nile virus (WNV) infection and identify factors associated with risk of death in infected equids.


METHODS
Cross-sectional study.


METHODS
484 equids in Nebraska and Colorado.


METHODS
Owners of 484 equids with laboratory-confirmed West Nile virus infection in Nebraska and Colorado were contacted by telephone, and a questionnaire was used to obtain information on signalment, management, clinical signs, date of disease onset, duration of disease, WNV vaccination status, and health status at the time of the interview.


RESULTS
137 of 482 (28.4%) animals died or were euthanatized. Ataxia, lethargy, muscle fasciculations, and weakness were the most common clinical signs of disease. Animals > or = 3 years old were more likely to die than were animals < or = 2 years old. Unvaccinated equids were twice as likely to die as were animals that had been vaccinated at least once prior to the onset of disease. Animals that were recumbent and unable to rise were 78 times as likely to die as were animals that never lost the ability to rise. Females were 2.9 times as likely to die as males. Two hundred seventy-one of 339 (79.9%) animals that survived recovered fully; mean duration of disease for these animals was 22.3 days.


CONCLUSIONS
Among equids with WNV infection, age, vaccination status, an inability to rise, and sex were associated with the risk of death.
Animal Population Health Institute, Colorado State University, Fort Collins, CO 80523, USA.
Patricia
P
Salazar
Josie L
JL
Traub-Dargatz
Paul S
PS
Morley
Delwin D
DD
Wilmot
David J
DJ
Steffen
Wayne E
WE
Cunningham
M D
MD
Salman
D000367:Age Factors; D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D000998:Antiviral Agents / Q000627:therapeutic use; D003120:Colorado / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy / Q000401:mortality*; D006736:Horses; D016015:Logistic Models; D008297:Male; D009329:Nebraska / Q000453:epidemiology; D012307:Risk Factors; D012737:Sex Factors; D016019:Survival Analysis; D016896:Treatment Outcome; D014611:Vaccination / Q000706:statistics & numerical data / Q000662:veterinary*; D014901:West Nile Fever / Q000188:drug therapy / Q000401:mortality / Q000662:veterinary*; D014902:West Nile virus / Q000472:pathogenicity*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D000998:Antiviral Agents