An Outbreak of Varicella-like Disease in Great Apes at Melbourne Zoo, Australia
Five gorillas and two orangutans developed signs of varicella-like disease over a 31-day period. The first case was an adult male gorilla presenting with lethargy and inappetence. Five to eight days later, pruritic vesicular lesions progressively appeared on his face, trunk, and hands. He was anesthetized on day 9 and blood collected for serology, returning a strong positive result for varicella-zoster (V-Z) IgM and negative for V-Z IgG. A presumptive diagnosis was made of V-Z infection. V-Z serology was subsequently performed on banked serum from 10 apes in direct and indirect contact with the affected animal. Three had strong IgG titres and three had borderline titres, indicating prior exposure to V-Z virus. All seronegative and two borderline animals subsequently developed similar clinical signs in two “waves” of onset, commencing 17 and 31 days respectively after presentation of the index case.
Varicella-like illness has been previously reported in young great apes all in very close contact with children, and in two reports, with known exposure to human V-Z infection.1-3 Human V-Z virus was isolated from lesions in two of these cases.2,3 Although virus was not isolated in the cases reported here, the clinical signs, incubation period and serologic findings were all strongly suggestive of V-Z infection; however, the animals only had close contact with zoo staff and there was no known exposure to an infected human. As the virus is capable of travelling long distances, we speculate that the index case resulted from aerosol spread from a zoo visitor.
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2. Myers, M.G., L.W.Kramer, and L.R.Stanberry. 1987. Varicella in a gorilla. J. Med. Virol. 23:317–322.
3. White, R.J., L.Simmons, and R.B.Wilson. 1972. Chickenpox in young anthropoid apes: clinical and laboratory findings. J. Am. Vet. Med. Assoc. 161:690–692.