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Prevalence of hepatitis B virus infection among Cercopithecidae monkeys in Cameroon

Hepatitis B virus (HBV) infection represents a worldwide health problem, affecting approximately one-third of the world’s human population and accounting for approximately one million deaths from chronic liver disease and hepatocellular carcinoma each year. Human populations in South-East Asia, sub-Saharan Africa, Central and South America show particularly high frequencies of HBV infection. Hepatitis B virus infection has also been documented in non-human primates (NHP) including chimpanzees and gorillas in sub-Saharan Africa [6, 13], gibbons and orangutans in South-East Asia [3, 13]. A highly divergent hepadnavirus distantly related to human HBV groups was recently isolated from a woolly monkey (Lagothrix lagothrica), a New World primate found in Central and South America [4]. Apart from humans and NHP, a range of highly genetically divergent HBV-like viruses have been detected in New World rodents such as woodchucks (Marmota monax) [2], ground squirrels (Spermophilus beecheyi) [11] and artic ground squirrels (S. parryii) [14] and a range of bird species [ducks (Anas platyrhyncha), geese (Branta hutchinsii) and grey heron (Ardea cinerea)] [1, 7, 12]. Even if HBVlike viruses are widely distributed in numerous species ranging from great apes to rodents, an HBV counterpart has not been reported in Cercopithecidae monkeys since all [6, 13] but one [3] previous studies failed to detect HBV infection among them. In spite of the fact that they share the same geographical habitat, HBV variants infecting great apes and humans in Central Africa and South-East Asia are genetically distinct from each other, providing evidence for the existence of separate indigenous virus populations. Although there is currently no evidence that human populations have been or are infected with great apes-associated HBV variants, the existence of this NHP reservoir of HBV could represent a handicap for the eradication of human HBV infection. It is therefore necessary in endemic areas to document the frequency of HBV infections in human and NHP populations. In a previous study, we show a high prevalence of HBV infection in chimpanzees (6.9%) and gorillas (11.6%) populations in Cameroon [9]. No information is available on the prevalence of HBV infection in Cercopithecidae monkey populations in Cameroon. We thus investigated the presence of HBV in plasma samples from wild-born Cercopithecidae monkeys originating from Cameroon. Plasma samples from 181 Cercopithecidae monkeys were available for screening (Table 1). These samples were collected from 1997 to 2006 from wild-born orphaned monkeys living mainly in the Southern rain forest areas of Cameroon. These animals have been transferred to zoos or rescue centres, generally after their mothers had been killed by hunters. On arrival, they were put into quarantine and samples collected for routine veterinary screenings, including HBV detection. This screening was performed to note serological status of animals in the wild before any contact with the other animals in these centres. Healthy animals were then integrated into specific communities. The animals included in this study were cared for and used humanely. Plasmas collected on ethylene diamine tetra-acetate tubes were sent to the Centre Pasteur of Cameroon (CPC) for analyses. The subspecies origin of these animals was determined by mitochondrial DNA (mtDNA) analysis as described previously [8].