The effect of rangeland degradation on gastro-intestinal parasite infections of Ankole cattle in the Mutara Rangelands, Rwanda

Abstract

The distribution of gastrointestinal (GI) parasites across landscapes is known to be closely related to the spatial distribution of hosts. In gastrointestinal parasites with environmental life stages, the dynamics of the parasite can also be affected by geophysical and ecological components of the environment. This is particularly relevant for domestic livestock species, which are kept across a range of different habitat types with varying quality, and are thus exposed to a wide range of environmentally robust parasite species. In my study, I examined the effect of environmental and anthropogenic parameters on the prevalence and intensity of GI parasites across a free-ranging stock of Ankole cattle in the Mutara rangelands of northeastern Rwanda. Prevalence and intensity of each parasite type (i.e., ‘strongyle-type’ nematodes, Strongyloides spp., Monezia spp., and coccidian Eimeria spp.) were used as dependent variables. I assessed 16 ecological and anthropogenic factors related to land-use form, climate and conservation-political history. I found the prevalence and intensity of Eimeria spp. had a positive relationship with vegetation-related effects (grass biomass, herb and grass frequency, tree canopy cover). The risk of Eimeria spp. infections was significantly higher in wet season than in dry season. By contrast the intensity of ‘strongyle-type’ nematodes was higher in dry than in wet season, and was negatively related to grass biomass and positively to soil compaction, suggesting that ‘strongyle-type’ nematode infections increase with increasing degradation (increased soil compaction and low grass biomass). Moreover, ‘strongyle-type’ nematode prevalence and intensity were negatively correlated with goat/sheep density, indicating a ‘dilution effect’ of GI infections between domestic livestock species.