Simian foamy virus transmission from apes to humans, rural Cameroon

Abstract

Simian virus infections of humans are an increasing public health concern. Simian foamy virus (SFV) infections have been reported in persons occupationally exposed to nonhuman primates and in a few hunters in Cameroon. To better understand this retroviral zoonosis in natural settings, we studied persons who lived in southern Cameroon, near nonhuman primate habitats. First we studied a general population of 1,164 adults; 4 were SFV positive according to serologic and molecular assays. Then we studied 85 persons who reported having been bitten or scratched by nonhuman primates; 7/29 (24.1%) of those who had contact with apes (gorillas or chimpanzees) were SFV positive, compared with only 2/56 (3.6%) of those who had had contact with monkeys. These data demonstrate efficient transmission of SFVs to humans in natural settings in central Africa, specifically following ape bites, and viral persistence in the human host.

Figure 1

Geographic distribution in Cameroon of the studied populations and the 13 persons infected by simian foamy virus (SFV), according to serologic and molecular results. Red, SFV-positive persons from the hunter study; green, SFV-positive persons from the retrospective study; blue circle, Pygmy area; violet circles, Bantu areas.

Figure 2

A) Western blot (WB) results based on chimpanzee (cpz) simian foamy virus (SFV) antigens. B) WB results based on monkey simian foamy virus antigens originating from participant AG16. C) Example of sero-indeterminate samples (lanes 1–7) and negative samples (lanes 8–13), detected by cpzSFV WB. Last lane (POS cpz), serum from an SFV-positive chimpanzee.

Figure 3

Wounds resulting from bites or scratches from a nonhuman primate. A) Participant no. 801001. B) Participant no. AG16. C) Participant no. 210301.

Figure 4

Immunofluorescence and electron microscopy results. A) Typical multinucleated giant cells with a clear seroreactivity of AG16 antigens, determined by using an immunofluorescence assay with positive anti–foamy virus serum, on BHK-21–infected cells cocultivated with stimulated peripheral blood mononuclear cells. B) Electron microscopy of ultrathin sections from cells infected by AG16 foamy virus.

Figure 5

Semiquantitative PCR for integrase and β-globin genes using AG15 peripheral blood buffy-coat DNA. Lanes 1–7 and 10–16, serial dilutions of the DNA from 500 ng to 0.5 pg; lanes 8 and 17, negative controls; lanes 9 and 18, positive controls; M, 100-bp ladder.