1. Desert Ecological Research Unit of Namibia, P.O. Box 1592, Swakopmund, Namibia 9000
2. Department of Physiology, University of the Witwatersrand, Medical School, 7 York Road, Parktown, 2193 Republic of South Africa
3. Central Veterinary Laboratory, Parasitology Section, Directorate Veterinary Services, Windhoek, Namibia 9000