Clinical signs of West Nile virus encephalomyelitis in horses during the outbreak in Israel in 2000

Abstract

Between August and October 2000, 76 horses were reported by veterinary practitioners as having signs of a neurological disorder, varying from an involvement of the spinal cord alone to the entire central nervous system; 15 of the horses died or were euthanased as a result of their grave prognosis or secondary complications. At the same time, an outbreak of West Nile virus infection affected people and birds, principally domestic geese. West Nile virus was isolated from four of the horses with encephalomyelitis and five other horses seroconverted, indicating that the virus was the probable cause of the outbreak in horses. Three of the cases from which the virus was isolated are described briefly and one case is described in detail. This horse behaved abnormally and had general proprioceptive deficits in all four limbs. Its neurological condition deteriorated after two days and severe inspiratory dyspnoea due to a failure to abduct the arytenoids necessitated a tracheostomy. It died on the fourth day and histological lesions were observed in the brain stem and grey matter of the spinal cord.

West Nile Virus Meningoencephalitis in a Suri Alpaca and Suffolk Ewe

“…8,10,12,13 Although the torticollis described in this alpaca was unusual, the clinical signs (ataxia and recumbency) and disease progression were similar to reported cases of fatal WNV encephalomyelitis in horses. 12,13 The clinical course in the ewe was more rapid than is typically described in horses. More abundant WNV antigen was demonstrated with IHC in the brain of the ewe than in the alpaca or is generally observed in positive horses evaluated at this laboratory.…”

West Nile virus infection of horses

“…In the outbreaks in Israel, WNV infections were reported in over 400 people, 325 of whom were hospitalised and 33 died. At least 75 horses were affected with encephalitis and 15 died, but, very unusually, there was also extensive mortality in birds, particularly geese [6,85].…”

Diagnosis of West Nile Virus Infection in Horses

“…From a population of over 500 horses in which WNV infection was suspected based on clinical signs, 5,16,17,[20][21][22][23] RTnPCR was performed on RNA extracted from ethylenediaminetetraacetic acid-anticoagulated blood of 140 horses. None of the 140 horses was previously vaccinated against WNV.…”

“…Diagnosis of WNV in horses is currently based on observation of compatible clinical signs, such as ataxia, paresis, paralysis, hyperesthesia, muscle fasciculations, seizures, or fever 5,16,17,[21][22][23] and on one or more of the following: isolation or reverse transcriptasepolymerase chain reaction (RT-PCR) detection of WNV from tissue, blood, or cerebrospinal fluid (CSF); a 4-fold increase in plaque reduction neutralization test (PRNT) antibody titers between paired serum samples taken 2 weeks apart; detection of IgM antibody to WNV by IgM-capture enzyme-linked immunosorbent assay (ELISA) or a neutralizing titer of Ͼ1:10 by PRNT in a single serum sample. However, widespread use of a WNV vaccine coupled with multiple years of natural exposure may make interpretation of PRNT serological results less definitive.…”