Implications of Simian Retroviruses for Captive Primate Population Management and the Occupational Safety of Primate Handlers

Abstract

Nonhuman primates can be naturally infected with a plethora of viruses with zoonotic potential, including retroviruses. These simian viruses present risks to both captive nonhuman primate populations and persons exposed to nonhuman primates. Simian retroviruses, including simian immunodeficiency virus, simian type D retrovirus, simian T-lymphotropic virus, and gibbon ape leukemia virus, have been shown to cause clinical disease in nonhuman primates. In contrast, simian foamy virus, a retrovirus that is highly prevalent in most nonhuman primates, has not been associated with clinical disease in naturally infected primates. Although it has been shown that human retrovirus infections with human T-lymphotropic virus and human immunodeficiency virus originated through multiple independent introductions of simian retroviruses into human populations that then spread globally, little is known about the frequency of such zoonotic events. In this article, exogenous simian retroviruses are reviewed as a concern for zoo and wildlife veterinarians, primate handlers, other persons in direct contact with nonhuman primates, and other nonhuman primates in a collection. The health implications for individual animals as well as managed populations in zoos and research institutions are discussed, the cross-species transmission and zoonotic disease potential of simian retroviruses are described, and suggestions for working safely with nonhuman primates are provided.

Non-Simian Foamy Viruses: Molecular Virology, Tropism and Prevalence and Zoonotic/Interspecies Transmission

“…A more comprehensive profile of all known New and Old World SFVs including PFV as shown in Figure 2 and Figure 3 illustrates the two entirely separated clades, closely correlating with Michael Heads evolution theory of the distribution of monkeys, mentioned below [45]. So far zoonotic transmission events of New World SFVs to humans have not been reported, thus leaving it open whether the New World SFVs have a comparable zoonotic potential like the Old World SFVs as it is proposed for SFV gor , SFV cpz and SFV agm in many publications [9,46,47,48,49]. Thus it would be interesting to study whether the lack of known New World SFV zoonoses is simply due to the lack of studies or whether it is related to the higher genetic divergence between humans and New World monkeys.…”

Molecular Ecology and Natural History of Simian Foamy Virus Infection in Wild-Living Chimpanzees

“…SFV infection of primates and humans is generally diagnosed by documenting virus specific anti-Gag antibodies in serum or plasma using ELISA and/or Western blot approaches [8],[10],[18],[19]. The infecting SFV strain is then molecularly characterized by amplifying viral DNA from peripheral blood mononuclear cell (PBMC) or other tissue DNA [8], [10], [11], [13], [16]–[18],[24],[26],[28].…”

“…This ancient relationship may be responsible for the non-pathogenic phenotype of SFV: Although highly cytopathic in tissue culture, the various SFVs do not seem to cause any recognizable disease in their natural hosts [2],[3],[14]. SFVs are highly prevalent in captive primate populations, with infection rates ranging from 70% to 100% in adult animals [2], [3], [5], [15]–[19]. Transmission is believed to occur through saliva because large quantities of viral RNA, indicative of SFV gene expression and replication, are present in cells of the oral mucosa [3], [20]–[22].…”

“…Indeed, the first “human foamy virus” [23] isolated from a Kenyan patient with nasopharyngeal carcinoma more than three decades ago was subsequently identified to be of chimpanzee origin [7],[8]. Since then, SFV strains from African green monkeys, baboons, macaques and chimpanzees have been identified in zookeepers and animal caretakers who acquired these infections through occupational exposure to primates in captivity [19], [24]–[27]. More recently, about 1% of Cameroonian villagers who were exposed to primates through hunting, butchering and the keeping of pet monkeys were found to be SFV antibody positive, and genetic analysis of three such cases documented infection with SFV strains from DeBrazza's monkeys, mandrills and gorillas [10].…”

Simian herpesviruses and their risk to humans

“…What is less well documented is the importance of specific guidelines, policies and procedures required for individuals working with RM to prevent zoonotic infections in humans. Some information can be found in the 5 th Edition of the Biosafety in Microbiological and Biomedical Laboratories, published by the CDC and NIH, but most NPRCs have rigorous education, training programs and protocols in place to ensure the safety of animal care staff, veterinarians and biomedical researchers who work working closely with RM to prevent zoonotic infection by simian herpesviruses, simian foamy virus or other yet unknown and identified viral pathogens [95, 96]. …”