Primate-to-human retroviral transmission in Asia

Disease risk analysis: a tool for primate conservation planning and decision making

Concern about emerging and re-emerging diseases plays an increasing role in conservation and management of both captive and free-ranging nonhuman primates (NHPs). Managers and policy makers must formulate conservation plans in an arena plagued by uncertainty, complexity, emotion, and politics. The risk analysis paradigm provides a framework that brings together scientists and policy experts to make better decisions for both people and animals. Risk analysis is a multidisciplinary, science-based process that provides an organized and logical approach for incorporating scientific information into policy development in the real world. By blending four specific goal-oriented stages-hazard identification, risk assessment, risk management, and risk communication-one can logically assess the probability that an adverse event, such as the introduction of an emerging disease into a naïve population, will occur. The following is a review of this process as it pertains to NHP conservation and risks associated with infectious diseases.

Foamy virus infection in primates

Foamy viruses (FV), the oldest known genus of Retroviridae, are unique among the retroviruses in having no disease association. It is not known why FV are non-pathogenic while infection by their closest relatives can be deadly. This may be related to the estimated 60 million years of coevolution of FV and their primate hosts. We review the current state of knowledge of FV infection, including information about the sites of viral replication and host immune responses, and discuss the role these may play in establishing persistent yet non-pathogenic infections. Whether FV has pathologic consequences in immunosuppressed hosts has not been thoroughly investigated. As most primates in HIV/SIV research are coinfected with FV, investigation into possible interactions between these viruses is of interest. The use of FV as a vector for gene therapy is also discussed.

Temple monkeys and health implications of commensalism, Kathmandu, Nepal

Humans in contact with macaques risk exposure to enzootic primateborne viruses.

The threat of zoonotic transmission of infectious agents at monkey temples highlights the necessity of investigating the prevalence of enzootic infectious agents in these primate populations. Biological samples were collected from 39 rhesus macaques at the Swoyambhu Temple and tested by enzyme-linked immunosorbent assay, Western blot, polymerase chain reaction, or combination of these tests for evidence of infection with rhesus cytomegalovirus (RhCMV), Cercopithecine herpesvirus 1 (CHV-1), simian virus 40 (SV40), simian retrovirus (SRV), simian T-cell lymphotropic virus (STLV), simian immunodeficiency virus (SIV), and simian foamy virus (SFV). Antibody seroprevalence was 94.9% to RhCMV (37/39), 89.7% to SV40 (35/39), 64.1% to CHV-1 (25/39), and 97.4% to SFV (38/39). Humans who come into contact with macaques at Swoyambhu risk exposure to enzootic primateborne viruses. We discuss implications for public health and primate management strategies that would reduce contact between humans and primates.

Modes of transmission and genetic diversity of foamy viruses in a Macaca tonkeana colony

BACKGROUND

Foamy viruses are exogenous complex retroviruses that are highly endemic in several animal species, including monkeys and apes, where they cause persistent infection. Simian foamy viral (SFV) infection has been reported in few persons occupationally exposed to non-human primates (NHP) in zoos, primate centers and laboratories, and recently in few hunters from central Africa. Most of the epidemiological works performed among NHP populations concern cross-sectional studies without long-term follow-up. Therefore, the exact timing and the modes of transmission of SFVs remain not well known, although sexual and oral transmissions have been suspected. We have conducted a longitudinal study in a free-breeding colony of Macaca tonkeana in order (1) to determine the prevalence of the infection by foamy viruses, (2) to characterize molecularly the viruses infecting such animals, (3) to study their genetic variability overtime by long-term follow-up of several DNA samples in a series of specific animals, and (4) to get new insights concerning the timing and the modes of SFVs primary infection in these monkeys by combining serology and molecular means, as well as studies of familial structures and long-term behavioral observations.

RESULTS/CONCLUSION

We first demonstrated that this colony was highly endemic for SFVs, with a clear increase of seroprevalence with age. Only 4.7% of immatures, and 43,7% of sub-adults were found seropositive, while 89.5% of adults exhibited antibodies directed against SFV. We further showed that 6 different strains of foamy viruses (exhibiting a very low intra-strain and overtime genetic variability in the integrase gene) are circulating within this group. This suggests a possible infection by different strains within an animal. Lastly, we provide strong evidence that foamy viruses are mostly acquired through severe bites, mainly in sub-adults or young adults. Most cases of seroconversion occur after 7 years of age; from this age individuals competed for access to sexual partners, thus increasing the likelihood of being wounded. Furthermore, all the serological and molecular data, obtained in this free-breeding colony, argue against a significant transmission of SFVs from mother or father to infants as well as between siblings.

Expanded tissue targets for foamy virus replication with simian immunodeficiency virus-induced immunosuppression

Foamy viruses (FV) are the oldest known genus of retroviruses and have persisted in nonhuman primates for over 60 million years. FV are efficiently transmitted, leading to a lifelong nonpathogenic infection. Transmission is thought to occur through saliva, but the detailed mechanism is unknown. Interestingly, this persistent infection contrasts with the rapid cytopathicity caused by FV in vitro, suggesting a host defense against FV. To better understand the tissue specificity of FV replication and host immunologic defense against FV cytopathicity, we quantified FV in tissues of healthy rhesus macaques (RM) and those severely immunosuppressed by simian immunodeficiency virus (SIV). Contrary to earlier findings, we find that all immunocompetent animals consistently have high levels of viral RNA in oral tissues but not in other tissues examined, including the small intestine. Strikingly, abundant viral transcripts were detected in the small intestine of all of the SIV-infected RM, which has been shown to be a major site of SIV (and human immunodeficiency virus)-induced CD4+ T-cell depletion. In contrast, there was a trend to lower viral RNA levels in oropharyngeal tissues of SIV-infected animals. The expansion of FV replication to the small intestine but not to other CD4+ T-cell-depleted tissues suggests that factors other than T-cell depletion, such as dysregulation of the jejunal microenvironment after SIV infection, likely account for the expanded tissue tropism of FV replication.

Risk assessment: a model for predicting cross-species transmission of simian foamy virus from macaques (M. fascicularis) to humans at a monkey temple in Bali, Indonesia

Contact between humans and nonhuman primates (NHPs) frequently occurs at monkey temples (religious sites that have become associated with free-ranging populations of NHPs) in Asia, creating the potential for NHP-human disease transmission. In March 2003 a multidisciplinary panel of experts participated in a workshop designed to model the risk of NHP-human pathogen transmission. The panel developed a risk assessment model to describe the likelihood of cross-species transmission of simian foamy virus (SFV) from temple macaques (Macaca fascicularis) to visitors at monkey temples. SFV is an enzootic simian retrovirus that has been shown to be transmitted from NHPs to humans. In operationalizing the model field data, laboratory data and expert opinions were used to estimate the likelihood of SFV transmission within this context. This model sets the stage for a discussion about modeling as a risk assessment tool and the kinds of data that are required to accurately predict transmission.

Human culture and monkey behavior: assessing the contexts of potential pathogen transmission between macaques and humans

An in-depth understanding of the contexts and patterns of human-macaque interactions can play an important role in assessing and managing the potential for pathogen transmission. The Padangtegal Monkey Forest in Bali, Indonesia, and the Upper Rock Nature Reserve in Gibraltar are two sites that have been relatively well studied in regard to human-macaque interactions. This article presents an overview of interaction patterns between humans and macaques at these sites along with a description of the cultural, demographic, and contextual differences between local and nonlocal humans at the sites. Differences in these two sites' interaction patterns included bite rates, the role of food in aggressive interactions, and the context in which the interactions took place. Similarities included overrepresentation by adult male macaques in interactions and a substantial impact by local cultural and demographic factors. These similarities and differences are interpreted as resulting from differences in macaque species and behaviors, and human demography, culture, and behavioral patterns.

Considering human–primate transmission of measles virus through the prism of risk analysis

Measles is a respiratory virus that is endemic to humans. Human-nonhuman primate (NHP) transmission of the measles virus has been shown to cause significant morbidity and mortality in NHP populations. We investigated serological evidence of exposure to measles virus in two free-ranging populations of macaques at the Bukit Timah (BTNR) and Central Catchment Nature (CCNR) reserves in Singapore and the Swoyambhu Temple in Katmandu, Nepal. At BTNR/CCNR none of the 38 macaques (Macaca fascicularis) sampled were seropositive for antibodies to measles virus. In contrast, at Swoyambhu 100% (n = 39) of the macaques (M. mulatta) sampled were seropositive for antibodies to the measles virus. Here the contrasting seroprevalences of the two sites are analyzed using risk analysis. These case studies show how risk analysis can be used to approach the phenomenon of cross-species pathogen transmission.

Prevalence of enzootic simian viruses among urban performance monkeys in Indonesia

Animal reservoirs are the most important sources of emerging infectious diseases that threaten human populations. Global travel and tourism bring ever-increasing numbers of humans into contact with animals, increasing the likelihood of cross species transmission of infectious agents. Non-human primates come into contact with humans in a variety of contexts and may harbor infectious agents with zoonotic potential. We investigated the prevalence of infection with enzootic simian viruses among 20 urban performance monkeys (Macaca fascicularis) in Jakarta, Indonesia. This report documents for the first time evidence of infection with four simian viruses in urban performance monkeys. Simian foamy virus was detected by PCR in 52.9% of the macaques. Antibodies to simian retrovirus were detected in 10.5% of the macaques. Antibodies to Cercopithecine Herpesvirus 1, were detected in 5.3% of the macaques. Similarly, antibodies to simian T-cell lymphotropic virus were detected in 5.3% of the macaques. No evidence of infection with simian immunodeficiency virus was detected in these macaques. These results suggest that urban performance monkeys are a reservoir for enzootic simian viruses known to be capable of infecting humans.