Effects of rainfall, host demography, and musth on strongyle fecal egg counts in African elephants (Loxodonta Africana) in Namibia

Department of Biology, Stanford University, Stanford, California 94305, USA.
Journal of wildlife diseases (Impact Factor: 1.36). 01/2011; 47(1):172-81. DOI: 10.7589/0090-3558-47.1.172
Source: PubMed


Wild African elephants (Loxodonta africana) are commonly infected with intestinal strongyle parasites. Our objective was to determine baseline fecal strongyle egg counts for elephants in the northeast region of Etosha National Park, Namibia and determine if these numbers were affected by annual rainfall, elephant demography (age of individuals and composition of groups), and hormonal state of males. We found that matriarchal family group members have significantly higher fecal egg counts than male elephants (bulls). Among family group members, strongyle egg counts increased with age, whereas among bulls, strongyle egg counts decreased with age. Years of higher rainfall were correlated with decreased numbers of strongyle eggs among bulls. Finally, bulls were not affected by their physiologic (hormonal) status (musth vs. nonmusth). These results suggest that infection by strongyle parasites in Namibian African elephants is a dynamic process affected by intrinsic and extrinsic factors including host demography and rainfall.

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    • "Due to the relatively limited amount of work that has been carried out on these parasites in African elephants, very little is known about their identity, occurrence , importance, life cycles and transmission dynamics. Among African elephants, nematodes are frequently found (Kinsella et al., 2004; Fowler and Mikota, 2006; Thurber et al., 2011), with hookworms in particular reported to cause pathological lesions and haemorrhages in the bile ducts and liver, as well as the intestines (Obanda et al., 2011). The elephant-specific intestinal fluke Protofasciola robusta, likely to be an ancestral species within the Fasciolidae (Lotfy et al., 2008), has been associated with intestinal tissue damage, haemorrhage and death in free-ranging African elephants (Vitovec et al., 1984; Obanda et al., 2011). "
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    ABSTRACT: It is known from studies in a wide range of wild and domestic animals, including elephants, that parasites can affect growth, reproduction and health. A total of 458 faecal samples from wild elephants were analysed using a combination of flotation and sedimentation methods. Coccidian oocysts (prevalence 51%), and nematode (77%) and trematode (24%) eggs were found. Species were not identified, though trematode egg morphology was consistent with that of the intestinal fluke Protofasciola robusta. The following factors were found to have a significant effect on parasite infection: month, year, sex, age, and group size and composition. There was some evidence of peak transmission of coccidia and nematodes during the rainy season, confirmed for coccidia in a parallel study of seven sympatric domesticated elephants over a three month period. Nematode eggs were more common in larger groups and nematode egg counts were significantly higher in elephants living in maternal groups (mean 1116 eggs per gram, standard deviation 685) than in all-male groups (529, 468). Fluke egg prevalence increased with increasing elephant age. Preservation of samples in formalin progressively decreased the probability of detecting all types of parasite over a storage time of 1–15 months. Possible reasons for associations between other factors and infection levels are discussed.
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    • "The increase of strongyle egg counts with age in meerkats is in accord with other studies. In African elephants Loxodonta africana and plain zebra Equus quagga, strongyle egg count is lower in younger family group members than in older animals (Thurber et al. 2011; Fugazzola and Stancampiano, 2012). The pattern of infection observed in this study suggests chronic exposure, and accumulation of infective parasite stages over time. "
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