Background:  The recognition that AIDS originated as a zoonosis heightens concerns associated with human infection with simian retroviruses endemic in nonhuman primates, including simian immunodeficiency virus (SIV), simian type D retrovirus (SRV), simian T-cell lymphotropic virus (STLV), and simian foamy virus (SFV). Although few simian retrovirus infections in persons occupationally exposed to nonhuman primates have been reported, the characteristics and significance of these zoonoses are not fully defined. We report results from the surveillance of 4 simian retroviruses in persons working with nonhuman primates, and characterize new zoonoses.

Methods:  Consenting participants from North American institutions provided a serum sample for serologic testing for SIV, SRV, STLV, and SFV. Seropositive persons were interviewed regarding their exposure history, asked about their current general health status, and asked to provide archived sera to determine the duration of seropositivity. PCR testing was performed on peripheral blood lymphocyte DNA from seropositive persons. Phylogenetic analysis was done to determine the nonhuman primate species origin of the infections. Samples from spouses of seropositive persons were also tested by PCR and serology.

Results:  Testing of sera from 418 participants from 15 research centers and zoos identified no STLV infection. Sera from 2 persons with known SIV infection were positive for SIV. Sera from 2 persons were positive for SRV (0.48%) but PCR testing and virus isolation were negative in both cases. Seroreversion was seen in one SRV-seropositive person. In contrast, sera from 14 persons (3.35%; 12 males, 2 females) were found to be SFV positive. SFV integrase sequences were PCR-amplified from the peripheral blood lymphocyte DNA available from 13 cases. Phylogenetic analysis showed SFV infection originating from African green monkeys (n = 1), baboons (n = 4), and chimpanzees (n = 8). Archived sera, available from 12 cases, documented minimal SFV seropositivity of 0.5 to 26.0 years (median 15.5 years). All 13 cases report general good health. Wives of 6 SFV cases were tested and remain uninfected; 11 SFV cases reported donating blood more than once; 6 (54.5%) were seropositive at the time of donation.

Conclusions:  Our study documents persistent SFV infection originating from 3 nonhuman primate species in occupationally exposed workers and shows that simian retroviruses cross into humans more frequently than previously thought. These findings highlight the importance of defining the public health significance of these zoonoses.

Keywords: zoonoses; simian; retroviruses