Heterogeneity in patterns of helminth infections across populations of mountain gorillas (Gorilla beringei beringei)

Abstract

Conservation efforts have led to the recovery of the endangered mountain gorilla populations. Due to their limited potential for spatial expansion, population densities increased, which may alter the epidemiology of infectious diseases. Recently, clinical gastrointestinal illnesses linked to helminth infections have been recorded in both gorilla populations. To understand drivers and patterns of helminth infections we quantified strongylid and tapeworm infections across both Virunga Massif and Bwindi populations using fecal egg counts. We assessed the impact of age, sex, group size, season and spatial differences used as a proxy, which reflects observed variation in the occurrence of gastrointestinal problems, vegetation types, gorilla subpopulation growth and associated social structure on helminth infections. We revealed striking geographic differences in strongylid infections with higher egg counts mostly in areas with high occurrences of gastrointestinal disease. Increased helminth egg counts were also associated with decreasing group size in some areas. Observed spatial differences may reflect mutual effects of variations in subpopulation growth rates, gorilla social structure, and vegetation associated with altitude across mountain gorilla habitat. Helminth infection intensities in Virunga gorillas were lowest in the youngest and the oldest animals. Elucidating parasite infection patterns of endangered species with low genetic diversity is crucial for their conservation management.

Gastrointestinal symbiont diversity in wild gorilla: A comparison of bacterial and strongylid communities across multiple localities

“…Alternatively, this variation may be detrimental to host health or an indication of host illness, with both strongylid infections and bacterial microbiome variation previously linked to poor host health in NHPs (Amato et al, 2013;Clayton, Al-Ghalith, et al, 2018;Krief et al, 2008;Petrželková et al, 2021;Terio et al, 2018).…”

“…The variation of gastrointestinal symbiont communities may reflect shifts beneficial to the host individuals, with different bacterial taxa believed to aid digestion of particular food types. Alternatively, this variation may be detrimental to host health or an indication of host illness, with both strongylid infections and bacterial microbiome variation previously linked to poor host health in NHPs (Amato et al, 2013; Clayton, Al‐Ghalith, et al, 2018; Krief et al, 2008; Petrželková et al, 2021; Terio et al, 2018). Applying the HTS methodologies presented in this research to strongylid communities of other NHPs, principally great apes, provides an exciting opportunity to better understand how ecological factors may erode primate–strongylid evolutionary relationships.…”

“…Similarly, strongylid infections are often asymptomatic in great apes but infections have been linked to clinical manifestation of disease (Cantacessi et al, 2012;Krief et al, 2008;Masi et al, 2012;Pit et al, 2001). Climatic changes, host density and host traits, such as sociality or body mass, are suspected to alter infections (Friant et al, 2016;Huffman et al, 1997;Petrželková et al, 2021).…”

“…Similarly, strongylid infections are often asymptomatic in great apes but infections have been linked to clinical manifestation of disease (Cantacessi et al, 2012; Krief et al, 2008; Masi et al, 2012; Pit et al, 2001). Climatic changes, host density and host traits, such as sociality or body mass, are suspected to alter infections (Friant et al, 2016; Huffman et al, 1997; Petrželková et al, 2021). Consequently, ongoing habitat encroachment may increase the likelihood of clinical manifestations of parasite infections within gorillas, while gorillas also have potential to serve as zoonotic pathogen reservoirs for humans (Bittar et al, 2014; Raoult, 2012; Wolfe et al, 1998).…”

Association of human disturbance and gastrointestinal parasite infection of yellow baboons in western Tanzania

“…It is debated if intensity of parasite infection is linearly correlated with eggs/cysts shed in faeces, due to temporal variation of egg/cyst output [ 61 – 63 ]. However, with various studies identifying a linear relationship between egg output and adult worm burden within the host [ 64 – 66 ], and a lack of data for wild baboons, we assume egg/cyst output still provides a reliable insight into parasitic infections, as done previously in parasitic research of both Papio [ 39 ] and other NHP hosts [ 67 – 70 ].…”