A STUDY ON BOVINE TRYPANOSOMOSIS, TSETSE CHALLENGE AND EFFICACY OF ISOMETAMIDIUM CHLORIDE IN AMARO SPECIAL DISTRICT, SOUTHERN ETHIOPIA
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2008-06
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Abstract
Among livestock diseases tsetse-transmitted trypanosomosis, have been incriminated as the predominant elements in the extreme deterioration of animal resources in sub-Saharan region; Ethiopia that holds the greatest potential for expanding livestock production. The part of Amaro special district particularly mid and low land is infested with tsetse fly where animal trypanosomosis is a serious threat to livestock production. Thus the objectives of the present study were: to determine the prevalence and impact of bovine trypanosomosis and seasonal density of tsetse flies; the efficacy of Isometamidium chloride on bovine trypanosomosis. The study was conducted from October 2007 to May 2008 in Amaro special district of SNNPR. The study design involved questionnaire survey, seasonal cross sectional studies of tsetse and trypanosomosis and assessment of Isometamidium chloride therapeutic efficacy. The questionnaire survey indicated that trypanosomosis is an important problem following erratic rain fall affecting the animals and impeding agricultural activity of the area. The entomological survey revealed that Glossina pallidipes species was the only prevalent species along with other biting flies (Tabanids and Stomoxys). The apparent density of flies was significantly higher in the late rainy season 1.62 fly/trap/day,2.37 and 1.6 for G. pallidipes, Tabanids and Stomoxys, respectively than the dry season where the density was 0.66, 1.12 and 1.03, respectively. The tsetse fly account 27 %, of the total fly catch Tabanids 42.6 %, and Stomoxys 29 % during late rainy season and 24.7 %, 35 %, 39.9 % during dry season. In the low lands (<1500 m.a.s.l) the apparent density for G. pallidipes was statistically significant higher (p<0.05) than the mid land areas (>1500 m.a.s.l) in both seasons. The G. pallidipes caught was higher in the bush lands vegetation type followed by grass wood land and altitudinal distribution limit was up to 1550.m.a.s.l. The apparent density of G. pallidipes fly was positively correlated (r=0.147) with prevalence of trypanosomes infection. The parasitological survey of 1136 animals (585 in the late rainy and 551 in the dry seasons) indicated trypanosomosis prevalence rate to be 27.35 % and 13.79 % in rainy and dry seasons, respectively which showed statistically significant difference (p<0.05) between seasons .The higher infection rate found in the low land areas 31.77 % and 15.45 % than the mid land areas 17.32 % and 12.68 % in the late rainy and dry season respectively indicated a statistically significant difference (p<0.05). T. congolense was the dominant species among the trypanosomes and account 61.02 % infection as compared to T. vivax 24.15 %, in the over all infections. The mean PCV value of parasitaemic and aparasitaemic animal was 21.92 % (CI=21.38-22.46) and 27.31 % (CI = 27.00-27.62) where as the over all mean values of PCV
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was 26.23 % (CI=25.89 -26.45). The regression analysis of herd average indicated that PCV decreased with increasing prevalence of trypanosomes infections with a negative regression coefficient of values (r= -0.31) in both seasons. A statistically significant difference (p<0.05) in trypanosomes infections between different age groups of cattle was also observed. A total of 69 parasitaemic cattle were selected from 3 PAs for therapeutic efficacy of Isometamidium chloride at the dose rate of 1mg/kg bw. Parasitaemia was demonstrated in 8 out of 69 cattle (11.60 %) with in 15 days; 11out of 61 animals (18.03 %) with in 30 days; 9 out of 50 (18 %) with in 60 days and 6 out of 41 (14.63 %) cattle with in 90 days. With in 90 days of post Isometamidium chloride treatment out of 69 animals 34 (49.28 %) relapsed. In the post treatment, T. congolense contributed for 75 %, 81.82 %, 77.78 % and 66.67 % of infections with in 15, 30, 60 and 90 days, respectively. It is evidenced that trypanosomosis is one of the most important problems for agricultural and animal husbandry operations; the situation is getting worse as control and prevention of trypanosomosis is facing challenges due to limitation of vector control activities and the development of drug resistance in Amaro special district, SNNPR.
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Amaro district, Isometamidium chloride, Prevalence, Relapse duration, Trypanosomosis, Tsetse fly