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Field and experimental investigations on bovine trypanosomosis and efficacy of selected trypanocidal drugs were undertaken in Konso district, southern Ethiopia, from September 2007 to April 2008, with major views to determine the prevalence and socioeconomic impacts of bovine trypanosomosis; assess the efficacies of selected trypanocidal drugs; and evaluate the propensity of Konso community to devote public resources to integrated tsetse/trypanosomosis control approaches. Questionnaire interviews, cross-sectional and experimental study designs were applied to collect relevant information. A structured questionnaire was designed and posed to randomly selected households and key informants to identify areas with high suspicion of drug resistance. Questions addressed main issues like herd structure and major livestock health problems; socioeconomic impacts of trypanosomosis; the sources, usage pattern and suspected failure of trypanocidal drugs, etc. Open-ended and close-ended questionnaire interviews were administered to randomly selected households to evaluate the propensity of the community to a holistic, integrated disease control. In order to identify areas with high trypanosome infection pressure and risk of drug resistance, initial cross-sectional study was undertaken on randomly selected cattle heads the monthly blood samples of which were examined through micro- haematocrit centrifugation and Buffy coat methods. Linear regression model was employed to assess the relationship between parasitological prevalence of trypanosomal infections and herd average PCV. In order to assess the therapeutic and prophylactic efficacies of the common trypanocidal drugs, ten zebu calves (Bos indicus) were experimentally infected with randomly selected field isolates of T. congolense, and treated with Diminazene aceturate (3.5 mg/kg BW) when the first peak of trypanosomal parasitaemia appeared. Based on deterioration in clinical and haematological parameters, relapsed calves were re-treated with Isometamidium chloride (0.5 mg/kg BW). Experimental animals were monitored for clinical as well as parasitological parameters on regular basis for over three months. The study results revealed trypanosomosis to be a major threat to livestock production with contrasting arrays of socioeconomic impacts; significant reductions in cattle production losses after tsetse control and a corresponding rise in mean holdings of draft oxen and use of animal traction over the same period; an indiscriminate use and increasing tendencies in mean annual expenditure on trypanocidal drugs at the household level. Contingent valuation study disclosed animus propensity of Konso community to devote VII both labour and monetary resources to support integrated tsetse/trypanosomosis control; household size, wealth status and educational background of household heads to be the major determinants influencing willingness to support integrated disease control. Cross-sectional study on bovine trypanosomosis indicated an overall parasitological prevalence of 17.0 % and 13.4 % during rainy and dry season, respectively, reflecting its significant temporal and spatial variation (p< 0.001); and T. congolense to be a dominant trypanosome species hampering livestock sub-sector in Konso district. Regression analyses on haematological findings disclosed a significant reduction (p<0.05) in the herd mean PCV with an increase in the prevalence of trypanosomosis; and that the reduction in herd PCV was significantly higher during dry season than in rainy season (p<0.001), suggesting that trypanosomosis is less-well tolerated during dry months. Results of drug sensitivity testing revealed the presence of T. congolense populations exhibiting resistance to Diminazene aceturate. In conclusion, the absence of improved veterinary service and indiscriminate use of poor-quality trypanocidal drugs have proven to boost the risk of drug resistance in Konso district. In light of the high likelihood of trypanocidal drug resistance in Ethiopia, the present findings could be a useful tool to improve trypanocidal drug usage strategies in the field, and could form baseline information to undertake holistic assessments of drug resistance across tsetse-infested areas of Ethiopia. It is recommended that integrated disease control approaches be adopted with chemotherapy restricted to clinically sick animals, and legislations be devised and harmonized to ensure the quality of trypanocidal drugs.



Community participation, Drug resistance, Integrated approach, Sensitivity test, Southern Ethiopia, Livestock, T. congolense