Mitochondrial DNA control region sequences of orangutans (Pongo pygmaeus) from six different populations on the island of Borneo were determined and analyzed for evidence of regional diversity and were compared separately with orangutans from the island of Sumatra. Within the Bornean population, four distinct subpopulations were identified. Furthermore, the results of this study revealed marked divergence, supportive evidence of speciation between Sumatran and Bornean orangutans. This study demonstrates that, as an entire population, Bornean orangutans have not experienced a serious genetic bottleneck, which has been suggested as the cause of low diversity in humans and east African chimpanzees. Based on these new data, it is estimated that Bornean and Sumatran orangutans diverged approximately 1.1 MYA and that the four distinct Bornean populations diverged 860,000 years ago. These findings have important implications for management, breeding, and reintroduction practices in orangutan conservation efforts.

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A high prevalence (42.6%) of hepatitis B virus (HBV) infection was suspected in 195 formerly captive orangutans due to a large number of serum samples which cross-reacted with human HBV antigens. It was assumed that such viral infections were contracted from humans during captivity. However, two wild orangutans were identified which were HBV surface antigen positive, indicating that HBV or related viruses may be occurring naturally in the orangutan populations. Sequence analyses of seven isolates revealed that orangutans were infected with hepadnaviruses but that these were clearly divergent from the six known human HBV genotypes and those of other nonhuman hepadnaviruses reported. Phylogenetic analyses revealed geographic clustering with Southeast Asian genotype C viruses and gibbon ape HBV. This implies a common origin of infection within this geographic region, with cross-species transmission of hepadnaviruses among hominoids.

A serological survey of confiscated orangutans was conducted to determine the prevalence of specific viral infections cross reacting with human viruses. Antibodies specific for human hepatitis A (HAV) and B (HBV) viruses, herpes simplex viruses (HSV), and human T-lymphotropic virus (HTLV types I and II), as well as for the simian type D retroviruses (SRV types 1 to 3) and simian immunodeficiency virus (SIV) were tested in samples from 143 orangutans. Results revealed a high prevalence of potential pathogens. The most prevalent viral infection found was HBV (59.4% prevalence) of which 89.4% of infected individuals seroconverted to the non-infectious state and 10.6% remained as chronic carriers. Antibodies to HAV, HSV, HTLV-1, and SRV were also detected but at a lower prevalence. There was no evidence of lentiviral infections in this group of animals. The results confirm the importance of quarantine and the need for diagnostic differentiation of virus infections to determine if they are of human origin or unique orangutan viruses.

We recently described orang-utan hepadnavirus (OuHV) (Warren et al., Journal of Virology, 73, 7860-7865, 1999). Phylogenetic analyses indicated that the various isolates of OuHV can be divided into two genomic variants. Two representatives from each genomic cluster were analysed both molecularly and phylogenetically. Their genome organization was highly similar to other hepadnaviruses of apes and humans. The complete genome sequences of the two OuHV types had an overall 5 % sequence difference. Research on 25 seropositive Bornean orang-utans showed that, of the 19 animals infected with one variant, 12 originated from East Kalimantan. Phylogenetic analysis was performed using the full-length genomes of various primate hepadnaviruses. The tree topology revealed one cluster of Old World hepadnaviruses that is divided into two subclusters, one consisting of the ape viruses, and the other comprising the human genotypes A-E. These data suggest that the great apes and gibbons have been infected with a common ancestor hepadnavirus. Hepatitis B virus (HBV) is a member of the familyHepadnaviridae, which consists of the avian hepatitis B-type viruses (avihepadnaviruses) and the orthohepadnaviruses, which infect mammals. In addition to the HBVs that infect humans, the orthohepadnaviruses include viruses which infect rodents such as ground squirrels (GSHV) (Marion et al., 1980) and woodchucks (WHV) (Summers et al., 1978), as well as hepatitis B-like viruses that infect nonhuman primates, like chimpanzees (ChHBV), gibbons (GiHBV), woolly monkeys (WMHBV), gorillas (GoHBV) and orang-utans (OuHV)