Veterinary Parasitology 119 (2004) 125–135 Trypanocidal drug resistance in eastern province of Zambia L. Sinyangwe a,1 , V. Delespaux b,∗,1 , J. Brandt b , S. Geerts b , J. Mubanga a , N. Machila a , P.H. Holmes c,d , M.C. Eisler c,d a Central Veterinary Research Institute, Balmoral, P.O. Box 33980 Lusaka, Zambia b Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium c University of Glasgow Veterinary School, Bearsden Road, Glasgow G61 1QH, UK d International Livestock Research Institute, Nairobi, Kenya Received 9 July 2003; received in revised form 28 October 2003; accepted 28 November 2003 Abstract A survey to investigate resistance to drugs used in the treatment of bovine trypanosomosis was conducted in the eastern province of Zambia between 1996 and 1998. A cross-sectional study was conducted in three districts (Petauke, Katete, Lundazi) at 34 village sampling sites selected at random from villages that had shown greater than 6% prevalence of bovine trypanosomosis during an earlier survey. A longitudinal study was conducted in same three districts over a 1-year period. The study sites were chosen from the cross-sectional study and included eight sites showing high trypanosomosis prevalence and where no control activities were recorded. Use was made of parasitological methods, tests of resistance in cattle and mice and isometamidium-ELISA. Overall mean prevalence of trypanosomosis was 14.4, with 96% of infections caused by Try- panosoma congolense. The remainder was caused by Trypanosoma vivax (2%) and Trypanosoma brucei (2%). Tests in mice showed that of the stabilates collected, 24 (34%) were resistant to only isometamidium chloride, 8 (11.3%) were resistant to only diminazene aceturate, 1 (1.4%) was resis- tant to both drugs, and 38 (53.5%) were sensitive to both drugs. At least 2 out of 27 stabilates tested in cattle appeared to be resistant to trypanocidal drugs, 1 to isometamidium and 1 to diminazene. Isometamidium could be detected in only 63 (4.1%) of 1526 serum samples from cattle in the study. Only 6 (2.8%) of 212 serum samples from trypanosome-infected cattle had serum levels of the drug above 0.4 ng isometamidium per ml serum which is indicative for drug resistance in the infecting parasite population. ∗ Corresponding author. Tel.: +32-3-247-6262; fax: +32-3-247-6268. E-mail address: vdelespaux@itg.be (V. Delespaux). 1 L. Sinyangwe and V. Delespaux contributed equally to this article as co-first authors. 0304-4017/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2003.11.007