Contents lists available at ScienceDirect Veterinary Parasitology journal homepage: www.elsevier.com/locate/vetpar Research paper Gastro-intestinal parasite infections of Ankole cattle in an unhealthy landscape: An assessment of ecological predictors Ping Sun a,b, ⁎ , Torsten Wronski c , Jean D. Bariyanga a , Ann Apio d a Faculty of Forest and Environment, University for Sustainable Development Eberswalde, Schicklerstraße 5, 16225 Eberswalde, Germany b Department of Biology, College of Science and Technology, School of Science, University of Rwanda, P.O. Box 117, Huye, Rwanda c Faculty of Science, School of Natural Sciences and Psychology, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK d Jomo Kenyatta University of Agriculture and Technology, Kigali Campus, P.O. Box 3373, Kigali, Rwanda ARTICLE INFO Keywords: Coccidian infections Strongyle-type nematodes Dilution effect Rangeland degradation Soil compaction Overgrazing ABSTRACT The distribution of gastro-intestinal (GI) parasites across landscapes is closely related to the spatial distribution of hosts. In GI parasites with environmental life stages, the vitality of parasites is also affected by ecological and landscape-related components of the environment. This is particularly relevant for domestic livestock species that are often kept across habitats with varying degrees of degradation, exposing them to a wide range of environmentally robust parasite species. In our study, we examined the effect of environmental and anthro- pogenic factors 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., Moniezia spp., and Eimeria spp.) were used as dependent variables. Two fixed factors related to season and conservation-political history, together with three principal components (con- densed from nine ecological variables) were used as independent covariates in a univariate General Linear Model (GLM). Major effects on the prevalence and intensity of strongyle-type nematodes and on the intensity of Eimeria spp. were found in that vegetation-related effects such as above-ground grass biomass in conjunction with a high degree of soil compaction had a negative relationship with these parasite types. These unexpected findings suggest that strongyle-type and coccidian infections increase with increasing rangeland degradation. Strongyle- type nematode prevalence and intensity were also negatively related to goat/sheep density, indicating a ‘dilution effect’ of GI infections between domestic livestock species. 1. Introduction Worldwide about 25% of the terrestrial surface is covered by ran- gelands with extensive pastoral systems. Approximately 16% of the human population in sub-Saharan Africa depends on this form of in- come (WISP, 2008; CBD, 2010; Holechek et al., 2017). Pastoralism is characterized by ensuring the stability of ecosystems through the fer- tilization of rangelands (Qu et al., 2016), by maintaining natural ve- getation and soils (Mwalyosi, 1992; Ren et al., 2012), capturing carbon (Davies and Nori, 2008), reducing soil erosion, facilitating the soil water holding capacity (Homewood and Rodgers, 1984) and by pro- viding habitat for wildlife (Averbeck et al., 2012). On the other hand, pastoralists are considered to be responsible for land degradation through ‘overgrazing’ (as a consequence of ‘overstocking’ by exceeding the carrying capacity), leading to increased soil erosion and compaction and the loss of plant cover (Thornes, 2007, Perevolotsky and Seligman, 1998). However, causes of rangeland degradation are manifold, including human factors such as the overuse of natural resources and agricultural mismanagement (FAO, 2003); Rota et al., 2009), but also climatic factors such as droughts or floods. Depending on the climatic characteristics of rangeland ecosystems, grazing can have both, a po- sitive and a negative impact on vegetation and soils (Milchunas and Lauenroth, 1989; Calvosa et al., 2009; Fox et al., 2012). Environmental degradation of rangelands is also suspected to in- crease the prevalence of zoonotic diseases and the emergence of pre- viously well controlled parasitic infections (FAO, 1999); Smolinski et al., 2003). Overstocking with domestic livestock, for example, is held accountable for increasing rates of infectious diseases and helminth infections in cattle (Pandey et al., 1993; Swai et al., 2006; Gupta et al., 2012; Taj et al., 2014). Helminthosis, especially gastro-intestinal (GI) nematodes, are regarded a major emerging health threat to livestock and humans (WHO, 1979; Stear et al., 1997; Mas-Coma et al., 2008). Like all organisms, parasites are embedded in complex interactions with their abiotic and biotic environments (Poteet, 2006). Due to https://doi.org/10.1016/j.vetpar.2018.01.023 Received 24 June 2017; Received in revised form 20 January 2018; Accepted 27 January 2018 ⁎ Corresponding author at: Faculty of Forest and Environment, University for Sustainable Development Eberswalde, Schicklerstraße 5, 16225 Eberswalde, Germany. E-mail addresses: sunping9@icloud.com (P. Sun), t_wronski@gmx.de (T. Wronski), baridamass@gmail.com (J.D. Bariyanga), a-apio@gmx.de (A. Apio). Veterinary Parasitology 252 (2018) 107–116 0304-4017/ © 2018 Elsevier B.V. All rights reserved. T