Retroviruses in Wild-Born Semi-Captive East African Sanctuary Chimpanzees (Pan troglodytes schweinfurthii)

Information on retroviruses infections in great apes is scarce, especially for apes kept in sanctuaries throughout Africa. To investigate the prevalence of retroviruses and possible transmission of different retroviruses originating from chimpanzees of different origin (Uganda, Congo and Rwanda), 38 wild-born captive orphan chimpanzees residing in a sanctuary on Ngamba Island were analyzed for retroviral infections. Samples from sanctuary chimpanzees were analyzed using enzyme-linked immunoassays and polymerase chain reactions (PCR). Viruses were characterized by phylogenetic analysis. All chimpanzees were negative for antibodies against Simian Immunodeficiency Virus (SIV) and Simian T-cell Leukemia Virus (STLV). However, 28/38 (73%) chimpanzees were positive to Simian Foamy Virus (SFV) by analysis of a 425-bp DNA segment obtained by PCR using generic integrase primers homologous to highly conserved portions of the polymerase gene. Phylogenetic analysis of SFV sequences obtained in this study formed four sub clusters within the specific SFV P. t. schweinfurthii clade with significant variability among the new SFVs strains. We provide evidence of on-going cross-transmission of SFV among chimpanzees within the sanctuary mostly likely through horizontal routes. We propose to test all chimpanzees introduced into sanctuaries for retroviral and other infections. This will help avoid the spread also of pathogenic viruses in captive populations.