Taxon, Arboreality, Sex, and Season—Factors Influencing Gastrointestinal Parasite Occurrence in Zoo‐Housed Non‐Human Primates

The emergence of anthelminthic resistance is a well-documented phenomenon in livestock and companion animals. Given the scarcity of new antiparasitic drugs, the implementation of effective, holistic anthelminthic control strategies is critical to preserving the efficacy of existing treatments. Understanding parasite-host-environment interactions is necessary to establish such strategies aiming to reduce the use of anthelminthic drugs, mitigate resistance, and ultimately improve animal health and welfare. This study analyzed 3767 fecal parasitological reports from non-human primates housed at a Swiss zoological institution over a 48-year period. Frequency of positive results was analyzed in relation to taxonomy, arboreality, sex, season, and mean monthly temperatures. At least one parasite was detected in 53.2% of the samples, with higher occurrence of protozoa (47.4%) than nematodes (7.8%) and cestodes (0.1%). Due to the large sample number and the extensive study period, it was possible to define taxon-specific parasite susceptibilities. The effect of arboreality on parasite occurrence was found to be negligible. Seasonal trends were evident, with the highest nematode occurrence in summer, whereas protozoa occurrence peaked in spring and winter. Comprehensive monitoring is a fundamental prerequisite for the development and implementation of targeted and effective deworming strategies. Such strategies extend beyond the regular administration of anthelminthics and include integrated management practices, consideration of environmental factors, and, ideally, ongoing monitoring of resistance patterns. A well-designed, holistic deworming strategy not only improves animal health and welfare and reduces the risk of zoonotic transmission but also reinforces a zoo's reputation as a center of conservation and education and contributes to the success of reintroduction programs.