Two cases of HIV and simian foamy virus coinfection reported

Two cases of coinfection with HIV and simian foamy virus (SFV) are reported in the May 1^st edition of the Journal of Infectious Diseases. Although the exact clinical significance of infection with SFV is unknown for HIV-positive individuals, there is some laboratory evidence that SFV may alter the natural history of SIV, which is similar to HIV, and that SFV-infected cells are more vulnerable to infection with HIV.

The investigators recommend that measures should be introduced to protect the blood supply from SFV, and that strategies to reduce human contact with mandrills and other primates should be developed to prevent transmission of SFV and other simian infections to humans.

People in contact with nonhuman primates have a risk of infection with the parasites, viruses and bacteria with which these creatures can be infected. HIV originated as a simian virus and was subsequently spread by person-to-person contact showing the potential public health consequences of infections harboured by nonhuman primates.

SFV is a retrovirus that is common in nonhuman primates that are caught from the wild or held in captivity. It can be spread easily between nonhuman primates by contact with infected bodily fluids, usually through grooming, biting, and possibly sexual contact. Although laboratory studies have shown that SFV can damage the cells of nonhuman primates, it does not appear to cause disease in these species.

There is a growing body of evidence suggesting transmission of SFV from nonhuman primates to humans is possible. Transmission of SFV from a wide range of ape and monkey species, including chimpanzee, gorilla, macaque, African green monkey, baboon and mandrill to humans have been suggested.

The ability of SFV to cause illness in humans, or be transmitted between humans is not yet fully understood, but no cases of disease in humans or sexual transmission between humans has been recorded so far.

Little is known about the geographical distribution of SFV among humans, including those infected with HIV in west central Africa.

Investigators therefore conducted an analysis of blood samples obtained from 139 sex workers, 41 patients with sexually transmitted infection, and 179 blood donors . The commercial sex workers and individuals with sexually transmitted infections were located in the Democratic Republic of the Congo, and the blood donors in the Cameroon. Samples were obtained between 1985 and 2000.

Of the 139 samples obtained from commercial sex workers, one (0.72%) was found to be infected with SFV. This sample was also infected with HIV and was obtained in 1985. In addition, one sample (0.56%) from the 179 blood donors in the Cameroon was also SFV-infected, and once again this sample came from an HIV-positive individual.

Genetic analysis was performed on the sample from the blood donor and this showed that infection with SFV originated in a mandrill.

“Our identification of what are, to our knowledge, the first reported cases of coinfection with SFV and HIV heightens the importance of defining the clinical and public health consequences of zoonotic SFV infection, especially in the context of AIDS”, write the investigators.

Although it is unclear if infection with SFV will cause illness in HIV-positive individuals, they point to laboratory evidence that suggests that this may be possible. For example, SFV may alter the course of SIV-associated disease in the gut of macaques that have SIV-associated immunosuppression. Laboratory studies also suggest that SFV-infected human cells are more “permissive” of infection with HIV.

As SFV infection was found in both a sex worker and a blood donor, this suggests to the investigators that both sexual and bloodborne transmission of SFV may be possible. They note that blood donations are not screened for SFV and propose that their findings may indicate that such precautions need to be introduced. Canada, for example, recently banned blood donations from individuals who had had contact with nonhuman primates “to prevent the introduction of SFV and other primate microbes into the blood supply.”

Other studies in the Cameroon show that transmission of SFV, SIV and HTLV-1 from mandrills to humans has occurred, probably because of hunting and butchering. The investigators conclude, “these results suggest that frequent contact with mandrills in this region may explain the widespread zoonotic transmission of mandrill retroviruses. Effective strategies to reduce hunting of mandrills and other nonhuman primates are needed to help preserve these endangered species and to prevent their viruses from being transmitted to humans.”