Studies on Bovine Trypanosomosis and Efficacy of Selected Trypanocidal Drugs in Konso District, Southern Ethiopia

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Addis Ababa University


Studies on bovine trypanosomosis and efficacy of selected trypanocidal drugs involving field and experimental investigations were undertaken inK onso district, southern Ethiopia, from September 2007 to April 2008, with views to determine the prevalence a nd 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 prevalence study was conducted in representative sample of cattle by examination of monthly blood samples through micro- haematocrit centrifugation and Buffy coat methods. The relationship between parasitological prevalence of trypanosomal infections and herd mean pev was im·estigated through haematological examination during the rainy and dry seasons. 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. congolensc and, when parasitaemic, treated with Diminazene aceturate and Isometamidium chloride at dose rates of 3.5 and 0.5 mglkg body weight. respectively. Experimental animals were monitored for clinical and 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 VI integrated tsetse/trypanosomosis control; household SIze, wealth status and educational background of household heads to be the major determinants influencing willingness to support disease control. Cross-sectional study suggested an overall prevalence of 17.8 % and 14.2 % 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 subsector in Konso district. Regression analyses on haematological findings disclosed a significant reduction (p<0.05) in the herd mean rcv with an increase in the prevalence of trypanosomosis; and that the reduction in herd rcv 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 testil1g revealed the presence of T congolense populations exhibiting resistance to Diminazene aceturate and, possibly to Isometamidium chloride. 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 improv~ 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 recommendec that integrated disease control approaches be adopted with chemotherapy restricted to clinicall: sick animals, and legislations be devised and harmonized to ensure the quality of trypanocid2 drugs. Keywords: Community participation; Drug resistance; Integrated approach: Sensitivity te~ Southern Ethiopia; Livestock; T congolense; Trypanocidal drugs.



Community participation; Drug resistance; Integrated approach: Sensitivity te~ Southern Ethiopia; Livestock; T congolense; Trypanocidal drugs