The potential threat of Strongyloides spp. to mountain gorillas and public health in Bwindi Impenetrable National Park, Uganda

Soil-transmitted nematodes Strongyloides spp. parasitize a range of vertebrates, including endangered great apes and humans. Since 2018, the Mountain Gorilla Veterinary Project has observed an increase in gastrointestinal parasitic infections, including suspected strongyloidiasis in mountain gorillas in Bwindi Impenetrable National Park (BINP), Uganda. To investigate the prevalence of Strongyloides and potential cross-host transmission, we conducted noninvasive fecal sampling of mountain gorillas, olive baboons, domestic dogs and pigs. Samples were examined by coproscopy and real-time PCR followed by sequencing of the HVR-IV 18S rRNA and cox1 genes. Strongyloides prevalence was higher in mountain gorillas ranging near the park edge compared to forest interiors inside the park and among infant and juvenile mountain gorillas compared to other age groups. Strongyloides fuelleborni, a known zoonotic species, was identified in both baboons and mountain gorillas, suggesting sharing this particular parasite between the two primate species with potential implications for humans surrounding the park. In domestic animals, S. ransomi was detected in pigs, a zoonotic lineage S. stercoralis haplotype was detected in one dog, and another haplotype closely related to S. ransomi and S. venezuelensis was identified in another dog. The presence of zoonotic S. fuelleborni and S. stercoralis in Bwindi ecosystem poses a threat to mountain gorilla as well as human public health. Our study underscores the need for continued monitoring and community sensitization about the risk of cross-species transmission of these parasites.