Noninvasive Follow-Up of Simian Immunodeficiency Virus Infection in Wild-Living Nonhabituated Western Lowland Gorillas in Cameroon

Abstract

<jats:p>Simian immunodeficiency viruses infecting western lowland gorillas (SIVgor) are closely related to HIV-1 and are most likely the ancestors of HIV-1 groups O and P. At present, limited data are available on genetic diversity, transmission, viral evolution, and pathogenicity of SIVgor in its natural host. Between 2004 and 2011, 961 putative gorilla fecal samples were collected at the Campo Ma'an National Park, Cameroon. Among them, 16% cross-reacted with HIV-1 antibodies, corresponding to at least 34 infected gorillas. Combining host genotyping and field data, we identified four social groups composed of 7 to 15 individuals each, with SIV rates ranging from 13% to 29%. Eleven SIVgor-infected gorillas were sampled multiple times; two most likely seroconverted during the study period, showing that SIVgor continues to spread. Phylogenetic analysis of partial<jats:italic>env</jats:italic>and<jats:italic>pol</jats:italic>sequences revealed cocirculation of closely related and divergent strains among gorillas from the same social group, indicating SIVgor transmissions within and between groups. Parental links could be inferred for some gorillas infected with closely related strains, suggesting vertical transmission, but horizontal transmission by sexual or aggressive behavior was also suspected. Intrahost molecular evolution in one gorilla over a 5-year period showed viral adaptations characteristic of escape mutants, i.e., V1V2 loop elongation and an increased number of glycosylation sites. Here we show for the first time the feasibility of noninvasive monitoring of nonhabituated gorillas to study SIVgor infection over time at both the individual and population levels. This approach can also be applied more generally to study other pathogens in wildlife.</jats:p>

Origin of the HIV-1 group O epidemic in western lowland gorillas

“…As previously shown for SIVcpz-infected chimpanzees, SIVgor infection rates varied considerably among field sites, with some gorilla communities reaching prevalences of 20% or higher (16,17). Moreover, within two nesting groups, up to 40% of group members were infected, indicating efficient spread between individuals belonging to the same social unit.…”

“…A total of 56 SIVgor-infected gorillas have now been identified in this and previous studies. Partial env or pol sequences have been obtained for about half of them (9,16,17), although only small subgenomic fragments were amplified for most cases. Nonetheless, available sequences indicate greater similarity among SIVgor strains from the same field site than among strains from different field sites.…”

“…All fecal samples were examined for the presence of HIV cross-reactive antibodies using the INNO-LIA HIV I/II score confirmation test (Innogenetics), which contains HIV-1 and HIV-2 recombinant proteins and synthetic peptides coated as discrete lines on a nylon strip. This test was previously shown to detect SIVgor infection with greater than 90% sensitivity (16,17) and has even uncovered more divergent SIV lineages from other nonhuman primate species (2). Of a total of 2,932 gorilla fecal samples tested, 70 reacted with at least one HIV-1 antigen.…”

“…SIVcpz has been shown to have a substantive negative impact on the health, reproduction, and survival of chimpanzees in the wild, and has caused the decline of at least one chimpanzee community (25,27). Thus, studies on additional infected and uninfected gorilla populations are required to determine the impact of SIVgor on gorilla survival (17). Alternatively, it is possible that following its introduction, SIVgor may have not yet spread beyond southern Cameroon.…”

Guano exposed: Impact of aerobic conditions on bat fecal microbiota

“…For many communal species with stable home ranges or roosting behaviors (including some bat species), feces are typically abundant, easy to spot, and, depending on location (not deep inside abandoned mines or caves), require no significant training to collect. Such collection techniques have already been employed for monitoring endangered (e.g., gorillas ( Gorilla gorilla ) (Etienne et al., 2012; Liu et al., 2010)) or elusive wildlife (e.g., chimpanzees ( Pan troglodytes ) (Harvala et al., 2011; Makuwa et al., 2005) and bats (Walker et al., 2016)), largely alleviating technical and logistic challenges in obtaining samples from free‐ranging populations (Stallknecht, 2007). …”