West Nile virus encephalomyelitis in horses: 46 cases (2001).
OBJECTIVE
To determine signalment, clinical findings, results of diagnostic testing, outcome, and postmortem findings in horses with West Nile virus (WNV) encephalomyelitis.


METHODS
Retrospective study.


METHODS
46 horses with WNV encephalomyelitis.


METHODS
Clinical data were extracted from medical records of affected horses.


RESULTS
On the basis of clinical signs and results of serologic testing, WNV encephalomyelitis was diagnosed in 46 of 56 horses with CNS signs. Significantly more males than females were affected. Increased rectal temperature, weakness or ataxia, and muscle fasciculations were the most common clinical signs. Paresis was more common than ataxia, although both could be asymmetrical and multifocal. Supportive treatment included anti-inflammatory medications, fluids, antimicrobials, and slinging of recumbent horses. Results of the IgM capture ELISA and the plaque reduction neutralization test provided a diagnosis in 43 horses, and only results of the plaque reduction neutralization test were positive in 3 horses. Mortality rate was 30%, and 71% of recumbent horses were euthanatized. One horse that had received 2 vaccinations for WNV developed the disease and was euthanatized. Follow-up communications with 19 owners revealed that most horses had residual deficits at 1 month after release from the hospital; abnormalities were resolved in all but 2 horses by 12 months after release.


CONCLUSIONS
Our findings were similar to those of previous WNV outbreaks in horses but provided additional clinical details from monitored hospitalized horses. Diagnostic testing is essential to diagnosis, treatment is supportive, and recovery rate of discharged ambulatory horses is < 100%.
Porter
Michael B
MB
Department of Large Animal Clinical Sciences , College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA.
Long
Maureen T
MT
Getman
Liberty M
LM
Giguère
Steeve
S
MacKay
Robert J
RJ
Lester
Guy D
GD
Alleman
A Richard
AR
Wamsley
Heather L
HL
Franklin
Robert P
RP
Jacks
Stephanie
S
Buergelt
Claus D
CD
Detrisac
Carol J
CJ
D000818:Animals; D003937:Diagnosis, Differential; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis* / Q000188:drug therapy / Q000401:mortality; D006736:Horses; D008297:Male; D012189:Retrospective Studies; D012737:Sex Factors; D016896:Treatment Outcome; D014901:West Nile Fever / Q000175:diagnosis / Q000188:drug therapy / Q000401:mortality / Q000662:veterinary*; D014902:West Nile virus / Q000276:immunology / Q000302:isolation & purification