PS 14-182 - Initial assessment of helminth parasitism in Yucatan howler monkeys (Alouatta pigra) from Toledo District, Belize.

Abstract: Parasites are known to be sensitive bioindicators because frequency of infection and abundance measures can reflect the relative health of the community a host-parasite interaction is a part of. This is because for parasites with life histories involving multiple hosts to persist in a community, all hosts must co-occur and changes in environmental conditions that affect any of the hosts, or parasites, directly or indirectly could affect measures of infection and parasite diversity in a host population. Interestingly, non-human primates the world over face accelerated human expansion into previously undisturbed habitats, and recent studies on howler monkeys have measured positive, negative, or no relation between parasite diversity and landscape structure, with variabilities related to howler species and their associated biogeographical distribution. Here, we report on an initial assessment of parasite prevalence and species richness from 18 fecal samples collected from a protected population of endangered Yucatan black howler monkeys (Aloutta pigra) in a 466-ha intact tropical forest in the Toledo District of Belize over a two-week period in January 2022. Fecal samples were collected from underneath howler monkey roost trees within 12 hours of deposition and stored at room temperature in vials filled with 10% formalin. We identified two helminth parasites using microscopic techniques, with 12 samples (66.7%) showing infection with at least one. Eggs of Controrchis sp. (Trematoda) were found in 7 samples (38.9%), and an unidentified strongyle larvae (Nematoda) occurred in 4 samples (22.2%). Fifty percent of samples with parasites had single infections, and the other 50% were coinfections. Controrchis sp. is a gastrointestinal flatworm whose life cycle requires gastropods as first intermediate hosts, ants as second intermediate hosts and monkeys as definitive hosts all living in the same environment. Changes to the environment that impact any of these hosts will affect the completion of the Controrchis sp. life cycle. Strongyle nematodes use oral-fecal contact as a route for transmission, and environmental changes are likely to impact the survival of free-living infective stages, ultimately influencing infection levels. Additional samples collected over various seasons will be useful to better measure parasite diversity in this host population and test how parasites can be used as bioindicators of community and ecosystem health.