Orang-utan conservation: epidemiological aspects of health management and population genetics

Kristin Shannon Warren

This research addressed two important issues concerning conservation of orang-utans in Indonesia, the prevalence of diseases in orang-utans at reintroduction centres and the extent of intra-subspecific genetic variation between isolated populations of Bornean orang-utans. The research was conducted at the Wanariset Orang-utan Reintroduction Centre in East Kalirnantan fiom 1994 to 1997, during which time extensive field excursions were made throughout Borneo, and at the Biomedical Primate Research Centre in the Netherlands in 1998. Analysis of clinical records fiom 1991 to 1997 showed that during this period 339 orang-utans were admitted to Wanariset, of which 96 (28.3%) died and 108 (31.8%) were released. Studies were designed to identify and determine the prevalence of diseases, specifically gastro-intestinal parasites, tuberculosis and certain viral diseases. Further studies defined the factors associated with mortalities of orang-utans at the reintroduction centre. Gastro-intestinal parasites, in particular Strongyloides spp. and Balantidium coli, posed health problems for rehabilitant orang-utans. Strongyloides spp. and Strongyle sp. eggs and B. coli were detected in faecal samples from new arrivals, rehabilitant, released and wild individuals. Trichuris trichura was present in new arrivals, released and rehabilitant orang-utans, whereas Ascaris sp., and Cyclospora sp. were present only in rehabilitants. There was a high prevalence of B. coli in new arrivals (41.6%), rehabilitants (100%) and released individuals (100%) and a low prevalence in wild individuals (12.5%). Faecal egg counts of individuals infected with Strongyloides spp. showed that 47.8% of rehabilitants and 14.3% of new arrivals had egg counts over 1000 eggs/gm, 81.8% of released individuals had egg counts less than 500 eggslgm and all wild individuals had egg counts less than 100 eggs/mg. Strongyloidosis was the primary cause of death (21.9%) of rehabilitant orang-utans, prior to the incorporation of oral ivermectin into the parasite control program. There was a low prevalence of tuberculosis, which was detected in one individual (0.8%) and suspected to have caused the death of two others (2.1% of deaths). Diagnosis of tuberculosis in orang-utans was complicated by inaccuracies and difficulties in interpreting the diagnostic tests commonly used in humans and nonhuman primates. Further research is required to develop more reliable and accurate tests for the diagnosis of tuberculosis in orang-utans. A study of the serological prevalence of a number of viral infections in captive orangutans showed evidence of exposure to hepatitis B virus (42.6%), hepatitis A virus (34.9%), herpes simplex viruses (14.7%), simian D-type retroviruses (11.2%) and human T-lymphotrogic viruses (1.4%). There was no evidence of exposure to simian or human immunodeficiency viruses. Molecular studies to determine the origin of the hepatitis B virus, showed the virus was not of human origin as has been generally assumed, but was an indigenous virus which also occurred naturally in wild populations. The virus was subsequently named Orangutan Hepadnavirus. A molecular study using mitochondrial DNA was undertaken to determine whether there was significant genetic diversity between six isolated populations of wild orangutans within Borneo. It was concluded that there are at least four genetically distinct populations located in East Kalimantan, southwest Kalirnantdcentral Kalirnantan, northwest KalimantdSarawak, and Sabah. The findings of this research are discussed in terms of the implications for management policies for reintroduction centres, as well as for the conservation of wild populations. They will also be of relevance to zoos and primate centres.

Orang-utan conservation: epidemiological aspects of health management and population genetics

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