Acta Tropica 97 (2006) 108–116 Isometamidium sensitivity of Trypanosoma congolense stocks from cattle in West Africa tested in mice and the drug incubation infectivity test Tanja Nikola Knoppe a,1 , Burkhard Bauer b,2 , John J. McDermott c , Andrew S. Peregrine c,3 , Dieter Mehlitz a , Peter-Henning Clausen a,∗ a Institute for Parasitoloy and International Animal Health, Freie Universit¨ at Berlin, K ¨ onigsweg 67, D-14163 Berlin, Germany b Centre International de Recherche-D´ eveloppement sur l ′ Elevage en Zone Subhumide, 01 B.P. 454, Bobo Dioulasso 01, Burkina Faso c International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya Received 3 May 2005; received in revised form 8 September 2005; accepted 21 September 2005 Available online 27 October 2005 Abstract Four Trypanosoma (T.) congolense reference clones with known isometamidium sensitivity and 16 T. congolense stocks from cattle in K´ en´ edougou in south-western Burkina Faso, an area with known history of drug resistance, were characterised with the standard mouse test (SMT) and the drug incubation infectivity test (DIIT). All field stocks from K´ en´ edougou were resistant to 1.0mg/kg bw isometamidium in the SMT. Fourteen stocks (87.5%) also proved to be refractory to 10mg/kg bw. Testing with the DIIT confirmed the results of the SMT. By comparison to reference clones, all the K´ en´ edougou populations expressed high levels of resistance to isometamidium. © 2005 Elsevier B.V. All rights reserved. Keywords: Trypanosoma congolense; Isometamidium chloride; Drug sensitivity; Mice; Drug incubation infectivity test; Burkina Faso 1. Introduction Animal trypanosomosis is a major constraint to cat- tle production in the province of K´ en´ edougou, south- western Burkina Faso (Fig. 1)(Ou´ edraogo, 2002). However, animal traction is essential for the local ∗ Corresponding author. Tel.: +49 30 8386 2505; fax: +49 30 8386 2323. E-mail address: tropvetm@zedat.fu-berlin.de (P.-H. Clausen). 1 Present address: Intervet Innovation GmbH, Zur Propstei, D-55270 Schwabenheim, Germany. 2 Present address: Darlaten 23, D-31600 Uchte, Germany. 3 Present address: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ont., Canada N1G 2W1. agricultural economy in this region, which is mainly based on cotton production, as more than 70% of land ploughing is achieved through this means. Thus, trypanocidal drug use (isometamidium chloride and diminazene aceturate) is wide-spread due to the high risk of contracting trypanosomosis. For example, more than 45% of the total animal health expenditure is attributed to trypanocidal drug use (Ou´ edraogo, 2002). Resistance to the drugs used to control bovine try- panosomosis in K´ en´ edougou has been reported ear- lier. Pinder and Authie (1984) used mice to assess the drug sensitivity of Trypanosoma congolense cattle iso- lates from Samorogouan (Fig. 2). Stocks isolated during 1982–1983 were found to be four to eight times less 0001-706X/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.actatropica.2005.09.008