Noninvasive western lowland gorilla's health monitoring: A decade of simian immunodeficiency virus surveillance in southern Cameroon

Simian immunodeficiency virus ( SIV gor) causes persistent infection in critically endangered western lowland gorillas ( Gorilla gorilla gorilla ) from west central Africa. SIV gor is closely related to chimpanzee and human immunodeficiency viruses ( SIV cpz and HIV ‐1, respectively). We established a noninvasive method that does not interfere with gorillas' natural behaviour to provide wildlife pathogen surveillance and health monitoring for conservation. A total of 1,665 geo‐referenced fecal samples were collected at regular intervals from February 2006 to December 2014 (123 sampling days) in the Campo‐Ma'an National Park (southwest Cameroon). Host genotyping was performed using microsatellite markers, SIV gor infection was identified by serology and genetic amplification was attempted on seropositive individuals. We identified at least 125 distinct gorillas, 50 were resampled (observed 3.5 times in average) and 38 were SIV gor+ (seven individuals were seroconverters). Six groups of gorillas were identified based on the overlapping occurrence of individuals with apparent high rates of gene flow. We obtained SIV gor genetic sequences from 25 of 38 seropositive genotyped gorillas and showed that the virus follows exponential growth dynamics under a strict molecular clock. Different groups shared SIV gor lineages demonstrating intergroup viral spread and recapture of positive individuals illustrated intra‐host viral evolution. Relatedness and relationship genetic analysis of gorillas together with Bayesian phylogenetic inference of SIV gor provided evidence suggestive of vertical transmission. In conclusion, we provided insights into gorilla social dynamics and SIV gor evolution and emphasized the utility of noninvasive sampling to study wildlife health populations. These findings contribute to prospective planning for better monitoring and conservation.