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

Klára J Petrželková ,Anna Stryková,Jan Šlapeta,Peter Samaš,Barbora Červená,Méthode Bahizi,Dušan Romportl,Benard Ssebide,Barbora Pafčo,Kirsten Gilardi,David Modrý,Jeff Mapilanga,Arthur Kalonji,Jean Claude Tumushime,Jean Bosco Noheri,Gaspard Nzayisenga,Jean Paul Lukusa ,Robert Aruho,Antoine Mudakikwa,Carine Uwamahoro,Damien Mangura,Prosper Uwingeli,Zuzana Tehlarová ,Eddy Kambale Syaluha,Richard Muvunyi,Ricky Okwirokello,Felix Ndagijimana,Nicola Ferrari,Winnie Eckardt,Fred Nizeyimana,Julius Nziza,Rita Maria Cameira ,Luis Girón ,Linda J Lowenstine ,Michael R Cranfield ,Adrien Emile Ntwari

doi:10.1038/s41598-021-89283-4

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.

Highlights

Conservation efforts have led to the recovery of the endangered mountain gorilla populations
Endangered mountain gorillas (Gorilla beringei beringei) live in two populations and entirely within protected areas: one ranging within the Virunga Massif (VM) spanning the borders of Rwanda, Uganda and the Democratic Republic of the Congo (DRC), and the second ranging in the Bwindi-Sarambwe ecosystem in Uganda and DRC
Dataset 1 included nest samples collected across the whole VM and Bwindi Impenetrable National Park (BINP) during a single period (n = 392) and was used to investigate the effects of area, age/sex class and group size

Summary

Introduction

Conservation efforts have led to the recovery of the endangered mountain gorilla populations. Small groups, which are often one-male groups, may experience higher stress levels than large groups, which are often multi-male groups, because they have higher home range overlaps with neighboring groups, inter-group encounter rates, and are more vulnerable to infanticide by external m ales[14,15,16,17] All those observed changes in population dynamics, social structure, and habitat use may be altering stress levels and cause changes in pathogen epidemiology with subsequent health problems[12,18,19]. Gastrointestinal helminthiases are typically asymptomatic in wild non-human primates, but host factors like immune status, or extrinsic factors, such as habitat loss, fragmentation and other anthropogenic pressures, can alter the transmission dynamics of helminths and increase host susceptibility, which may exacerbate negative effects of infections on h ealth[46,47]. Many gorillas have exhibited weight loss, declining body condition and poor

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Conclusion