Prevalence of zoonotic nematode Calodium hepaticum varies with small mammal community diversity across a heterogenous landscape in Eastern Uganda

Calodium hepaticum (syn. Capillaria hepatica) is a generalist nematode that infects liver parenchyma of mammals worldwide and can cause human infections. Prevalence ranges from 0% to 100% in wildlife across small geographic areas, making it an ideal parasite for understanding ecological drivers of variation given intensive land use or cover change. Here, we quantify prevalence of Calodium hepaticum and present initial surveys of synanthropic small mammals. Cross-sectional rodent trapping was conducted within and around households over 2 consecutive dry seasons in 4 villages with differing land cover. DNA was extracted from liver tissue and the 18s rRNA gene of C. hepaticum was amplified to confirm presence of C. hepaticum. Landscape structural diversity was classified by tree crown density and mean canopy height derived from 30 m LiDAR data within a 0.5 km buffer. Multivariable binomial generalized linear models were fit to C. hepaticum prevalence. Calodium hepaticum infection was common (overall 34.5%, CI 95%: 27.9–41.0) and found in rodent and shrew species inside and outside residences. We observe village-level differences in prevalence (18.2–75.0%), with higher C. hepaticum prevalence associated with lower relative proportion of native rodent species to Rattus rattus (adjusted OR = 0.55, CI 95%: 0.33–0.92). Host diversity appears to be protective against parasite prevalence. Differences in molecular and gross parasitological identification highlight challenges in diagnosis and a need for more specialized molecular tools. Further investigation is required to understand individual host and community variation in pathogen infection intensity and implications for zoonotic risk.