Helminth infection dynamics in rehabilitating Javan slow lorises are driven by time since deworming rather than host traits.

Wildlife rehabilitation plays a central role in the conservation of threatened primates, yet parasite dynamics during captivity are rarely reported, particularly in relation to release readiness. We investigated gastrointestinal helminth infection patterns in rehabilitating Javan slow lorises (Nycticebus javanicus), a Critically Endangered species heavily impacted by the illegal wildlife trade. Using repeated fecal sampling (147 samples from 19 adults) and Bayesian mixed-effects models, we examined parasite richness, Shannon diversity, infection probability, and egg-shedding intensity in relation to release readiness status, sex, housing condition, and time since anthelmintic treatment. Four nematode taxa identifiable through egg morphology were detected: Strongyloides spp., strongylids, oxyurids, and Trichuris spp. Parasite richness and Shannon diversity showed no credible associations with release readiness or other host and management variables. In contrast, infection probability for Strongyloides spp. and strongylids increased with time since deworming, and Strongyloides egg counts exhibited a similar temporal pattern, consistent with post-treatment reinfection dynamics. Release readiness did not predict detection probability or parasite intensity for any parasite group, despite marked differences in captivity duration and health history between individuals deemed ready for release or not. These findings indicate that gastrointestinal helminth dynamics in rehabilitating slow lorises are driven primarily by treatment-related temporal processes and individual-level heterogeneity rather than coarse host classification. They also highlight the need for longitudinal parasite monitoring and for future work evaluating how infection dynamics, management interventions, and host health relate to rehabilitation and translocation outcomes.