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Variation in faecal water content may confound estimates of gastro-intestinal parasite intensity in wild African herbivores

Published online by Cambridge University Press:  23 July 2009

W.C. Turner ,
C.A. Cizauskas  and
W.M. Getz
W.C. Turner*
Affiliation:
Department of Environmental Science, Policy and Management, University of California, Berkeley, 137 Mulford Hall, Berkeley, CA94720-3112, USA
C.A. Cizauskas
Affiliation:
Department of Environmental Science, Policy and Management, University of California, Berkeley, 137 Mulford Hall, Berkeley, CA94720-3112, USA
W.M. Getz
Affiliation:
Department of Environmental Science, Policy and Management, University of California, Berkeley, 137 Mulford Hall, Berkeley, CA94720-3112, USA Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria0002, South Africa
*
*Fax: (+1) 510-666-2352 E-mail: wturner@nature.berkeley.edu
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Abstract

Estimates of parasite intensity within host populations are essential for many studies of host–parasite relationships. Here we evaluated the seasonal, age- and sex-related variability in faecal water content for two wild ungulate species, springbok (Antidorcas marsupialis) and plains zebra (Equus quagga). We then assessed whether or not faecal water content biased conclusions regarding differences in strongyle infection rates by season, age or sex. There was evidence of significant variation in faecal water content by season and age for both species, and by sex in springbok. Analyses of faecal egg counts demonstrated that sex was a near-significant factor in explaining variation in strongyle parasite infection rates in zebra (P = 0.055) and springbok (P = 0.052) using wet-weight faecal samples. However, once these intensity estimates were re-scaled by the percent of dry matter in the faeces, sex was no longer a significant factor (zebra, P = 0.268; springbok, P = 0.234). These results demonstrate that variation in faecal water content may confound analyses and could produce spurious conclusions, as was the case with host sex as a factor in the analysis. We thus recommend that researchers assess whether water variation could be a confounding factor when designing and performing research using faecal indices of parasite intensity.

Type
Research Papers
Information
Journal of Helminthology , Volume 84 , Issue 1 , March 2010 , pp. 99 - 105
Copyright
Copyright © Cambridge University Press 2009

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