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

Johnson, E.; Ajambo, D.; Capstick, M.; Arinaitwe, M.; Ericsson, O.; Besigye, F.; Raghwani, J.; Dennis, T. P. W.; Bogere, R.; Barungi, A. N.; Atuhire, A.; Rowell, C.; Annet, N.; Mohamed, A.; Moses, A.; Lamberton, P. H. L.; Tukahebwa, E.; Allan, K. J.; Faust, C. L.

doi:10.1101/2025.09.09.674808

bioRxiv · 10.1101/2025.09.09.674808

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

Johnson, E.·Ajambo, D.·Capstick, M.·Arinaitwe, M.·Ericsson, O.·Besigye, F.·Raghwani, J.·Dennis, T. P. W.·Bogere, R.·Barungi, A. N.·Atuhire, A.·Rowell, C.·Annet, N.·Mohamed, A.·Moses, A.·Lamberton, P. H. L.·Tukahebwa, E.·Allan, K. J.·Faust, C. L.

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Abstract

Identifying key drivers of pathogen infection prevalence and intensity in wildlife is essential to understand disease dispersal and transmission. Calodium hepatica (syn. Capillaria hepatica) is a generalist nematode that infects liver parenchyma of mammals worldwide and is capable of human infections. Prevalence ranges from 0-100% in wildlife, often varying across small geographic areas, making it an ideal parasite for understanding ecological drivers of variation. Here, we quantify prevalence of Calodium hepatica and present initial surveys of synanthropic small mammals in four villages representing differing land cover. Cross-sectional rodent trapping was conducted within and around households over consecutive dry seasons in Eastern Uganda. 18s rRNA gene of C. hepatica was amplified and a sub-set of PCR products sequenced to confirm presence of C. hepatica. Landscape structural diversity was classified by tree crown density and mean canopy height derived from 30m LiDAR data within a 0.5km buffer. Multivariable binomial generalised linear models were fit to C. hepatica prevalence. C. hepatica infection was common (overall 34.5%, CI95% 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. hepatica prevalence associated with higher relative proportion of Rattus rattus to other species (aOR=2.22 CI95% 1.30-3.85). Host diversity appears to be protective against parasite prevalence. Differences in molecular and macroscopy 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. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/674808v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@e9cfdaorg.highwire.dtl.DTLVardef@4d0f6dorg.highwire.dtl.DTLVardef@12fe43dorg.highwire.dtl.DTLVardef@1318d83_HPS_FORMAT_FIGEXP M_FIG C_FIG Key FindingsO_LIZoonotic reservoirs, including Rattus rattus, Mastomys erythroleucus and Crocidura olivieri, are abundant in human-modified habitats and show elevated levels of household incursion C_LIO_LIHigh prevalence of Calodium hepatica, a nematode endoparasite, was identified in a range of small mammal species C_LIO_LIHigher proportion of native small mammal species relative to Rattus rattus appears protective against zoonotic pathogen load, with higher village-level C. hepatica prevalence in ecologically depleted sites C_LIO_LISmall-holder agriculture may provide a dilution effect through secondary wildlife support and small mammal competition, while dense village settings potentiate C. hepatica prevalence C_LI

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Johnson, E., Ajambo, D., Capstick, M., Arinaitwe, M., Ericsson, O., Besigye, F., Raghwani, J., Dennis, T. P. W., Bogere, R., Barungi, A. N., Atuhire, A., Rowell, C., Annet, N., Mohamed, A., Moses, A., Lamberton, P. H. L., Tukahebwa, E., Allan, K. J., Faust, C. L.. 2025-09-12. Prevalence of zoonotic hepatic nematode varies with small mammal community diversity across a heterogenous landscape in Eastern Uganda. https://doi.org/10.1101/2025.09.09.674808

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