Simian immunodeficiency virus infections in vervet monkeys (Clorocebus aethiops) at an Australian zoo

A number of monkey species, including African green monkeys and African Ver vet monkeys (Chlorocebus aethiops), are frequently infected in the wild and in captivity with a Simian immunodeficiency virus strain, SIVagm, a primat e lentivirus.(1-3) Up to 50% of African green monkeys are estimated to be i nfected with SIVagm.(4) SIV strains are very closely related to HIV-2 strai ns, which are a cause of AIDS in humans, predominantly in western Africa, a lthough cases in Australia have also been reported.(5) It is generally thou ght that SIV is non-pathogenic in several natural hosts, including African green monkeys.(6) Nevertheless many SIV strains induce a profound immunodef iciency virtually identical to HIV-1 induced AIDS in humans when administer ed to Asian macaque species such as rhesus (Macaca mulatta) or pigtailed ma caques (M nemestrina).(7) SIV infection of Asian macaque species is frequen tly employed as an animal model for AIDS vaccine studies.(8) In November 1996 a group of 10 African Vervet monkeys were imported from th e USA for display at Victoria's Open Range Zoo in Werribee. Two animals in this group of monkeys later developed a fatal gastroenteric illness. These diagnoses led us to initiate SIV testing of the colony.