Are faecal egg counts reliable indicators of nematode infection in wildlife parasitology? The relationship between faecal egg counts and adult nematode counts in 3 species of African ungulates

Abstract Faecal egg counts (FECs) are often used as an indicator of nematode infections, but there is limited information on the relationships between FECs and adult nematode infections in African ungulates. We examined the relationships between FECs and the intensity of infection of adult gastrointestinal (GI) nematodes in 3 ungulate species: impalas, Aepyceros melampus ; blue wildebeest, Connochaetes taurinus ; and warthogs, Phacochoerus africanus , in the Kruger National Park, South Africa. Helminths were grouped into Strongyloides papillosus, Gaigeria pachyscelis and ‘other GI nematodes’ in impalas, and into S. papillosus and ‘other GI nematodes’ in blue wildebeest and warthogs. The prevalence of all groups of helminths was underrepresented in the faecal analysis when compared to adult nematode counts. A significant, albeit weak, positive correlation was found between FECs and adult nematode counts in impalas and blue wildebeest, while no correlation was detected in warthogs, possibly reflecting variation in the composition of the helminth communities of these hosts and/or differences in their dietary and digestive strategies. Metric comparisons between results obtained for seasonal variation or age- or sex-related differences in nematode prevalence and abundance in these hosts varied distinctly based on the methodology used. The results of this study show complex relationships between the FEC and adult nematode burdens among and within the 3 ungulate hosts and confirm that extrapolations made from FECs should be made judiciously.