Natural occurrence of Strongyloides spp. in vervet monkeys (Chlorocebus pygerythrus) in Kuti Wildlife reserve, Malawi : assessment of correlation between anthropogenic disturbance and Strongyloides spp. infection

Abstract: The geographic overlap between non-human primates and people is increasing, especially in tropical and subtropical countries. This inevitably creates a potential for anthropogenic and zoonotic transmission of parasites, which could harm both wildlife and human communities. Strongyloides spp. are obligate gastrointestinal nematodes that are relatively host specific, but transmission between species can occur. It is estimated that between 30-100 million people are infected by Strongyloides spp. worldwide. In this study the ubiquitous non-human primate Chlorocebus pygrerythrus was used as a model to investigate the relationship between anthropogenic disturbance and Strongyloides spp. infection. Chlorocebus pygrerythrus, more commonly known as vervet monkeys, are medium sized monkeys found in the east and south of Africa. They are highly adaptive to different habitats and are found in semi-deserts, snowy mountains, savannah to more anthropogenic environments such as villages and cities. Vervet monkeys spend a large amount of time foraging on the ground, making them susceptible to soiltransmitted helminths. The present study investigated the natural occurrence of Strongyloides spp. in two vervet monkey troops in Kuti Wildlife Reserve, Malawi. Faecal samples from each troop were analysed (n=60) and the results showed a significantly higher prevalence (p<0.0001) in the troop in close proximity to humans (83%) than in the troop with sparse human contact (6.7%). The findings were in line with a previous study performed by Thatcher (2018), were four different localities were included. Vervet monkeys on the sites with higher anthropogenic disturbance had a higher parasite load. This suggests that anthropogenic disturbance indeed does affect the prevalence of Strongyloides spp., although since the number of samples was low the results should be cautiously interpreted. Another interesting finding in the present study was that the troop with higher prevalence had a smaller sized home range, a factor which is linked to increased parasite load in previous studies. For future studies, correction for host density, larger sample size, more troops and molecular analysis to demonstrate host-shifts are suggested.