Prevalence and Phylogenetic Analysis of Hepatitis B in Captive and Wild-Living Pileated Gibbons (Hylobates pileatus) in Cambodia

Abstract : The risk of transmitting novel pathogens from released animals to wild conspecifics is an important consideration for reintroduction initiatives. Apart from infecting humans, hepatitis B virus (HBV) has been detected in nonhuman primates, including captive gibbons. Gibbons that test positive for HBV are removed from reintroduction programs as the presence of infection in wild populations is uncertain. The aim of this study was to determine the prevalence of HBV in wild-living gibbon populations in the southwest and northeast of Cambodia and compare HBV DNA strains collected from these animals with samples from wild-born captive gibbons at the Phnom Tamao Wildlife Rescue Center, Cambodia. We screened HBV infection in blood and stool samples from captive gibbons and stool samples from wild-living gibbons. We sequenced samples with detectable HBV DNA viral load in the HBV reverse transcriptase coding region overlapping with the S-gene. Eleven of twenty-four (46 %) wild-living pileated gibbons (Hylobates pileatus) from the southwest of Cambodia were positive for HBV. Phylogenetic analysis of HBV DNA sequenced from wild and captive gibbons revealed that viral strains were related and different from human strains. The presence of an HBV variant circulating in the wild similar to that found in captive pileated gibbons suggests 1) the strain identified is associated with the species, 2) wild-born captive gibbons positive for this strain became infected prior to captivity, and 3) it might be appropriate to release captive gibbons that test positive for specific serological markers of HBV, provided they are otherwise suitable candidates for reintroduction.