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Outbreak of Orthoreovirus-induced meningoencephalomyelitis in baboons
M M Leland1, G B Hubbard, H T Sentmore
1Department of Physiology and Medicine, Southwest Foundation for Biomedical Research, San Antonio, TX, USA.
Background And Purpose:
Spontaneous viral encephalitis is rare in the baboon; yet, during a 13-month period (1993-1994), eight juvenile baboons (Papio cynocephalus spp.) developed acute, progressive nonsuppurative meningoencephalomyelitis caused by an unknown agent. Clinical signs of disease included disorientation and truncal ataxia that rapidly progressed to hemiparesis or paraparesis. Clinicopathologic findings were not remarkable and appreciable gross lesions were not seen at necropsy. Microscopic examination revealed CNS lesions that were characterized by lymphoplasmacytic perivascular cuffing, microglial nodules, demyelination, axonal degeneration, vacuolization, and hemorrhage. Subsequently, a novel syncytium-inducing mammalian orthoreovirus was isolated from the brain tissue of five baboons with clinical signs of infection.
Methods:
To confirm the etiologic role of the orthoreovirus, two juvenile baboons were inoculated with the virus, then were monitored for 6 weeks.
Results:
Lesions similar to those seen in spontaneous cases were found in the CNS, and orthoreovirus was isolated from the brain of both animals.
Conclusion:
Analysis of the outbreak indicated juvenile baboons were most susceptible to disease and the virus had a possible incubation time of 46 to 66 days, but did not indicate a source of the virus or mode of transmission.