Acute neurologic disease occurred in a 25-yr-old male Barbary macaque (Macaca sylvanus) at the Toronto Zoo, on August 17th, 2002. The animal was housed with 10 other Barbary macaques, in an outdoor exhibit with access to indoor overnight housing. Clinical signs included severe ataxia, unresponsiveness to surroundings and bilateral nystagmus. Due to unrelated chronic intercurrent disease and the severe neurologic signs, the animal was euthanatized. Gross lesions consisted of moderate gingivitis, generalized severe muscle atrophy, and severe chronic bilateral femorotibial osteoarthritis. Microscopically, there was severe nonsuppurative meningoencephalitis, characterized by generalized gliosis, scattered glial nodules, and perivascular lymphoplasmacytic cuffs. Immunohistochemistry for West Nile virus (WNV) was positive, and the diagnosis was confirmed by reverse transcriptase-PCR amplification of viral genome and by isolation of WNV from the brain.
The Barbary macaque was the first clinical case of WNV infection recognized at the Toronto Zoo. To our knowledge, this is also the first case of naturally occurring WNV infection in a primate in North America. The animal was infected in mid-August, at which time the prevalence of WNV was high in southern Ontario. All other zoo species affected were birds, and included a black-billed magpie (Pica pica), a red-tailed hawk (Buteo jamaicensis), two green-naped lorikeets (Trichoglossus haematodus haematodus), two American kestrels (Falco sparverius), five loggerhead shrikes (Lanius ludovicianus) and an American flamingo (Phoenicopterus ruber ruber). They subsequently presented with WNV-associated neurologic signs or sudden death.