Epidemiology of bovine trypanosomosis in the Abay (Blue Nile) Basin areas of Northwest Ethiopia

The study was conducted between September 2003 and April 2004 in Denbecha and Jabitehenan weredas (districts) located in the lowland (< 1600 m) and midland (1600-2000 m) areas. It generated a baseline data on the epidemiology of trypanosomosis and community awareness regarding the disease in the Abay (Blue Nile) Basin areas of Northwest Ethiopia. A questionnaire survey revealed trypanosomosis to be the most important problem affecting animals and impeding agricultural activities in the areas. Glossina morsitans submorsitans was the only tsetse fly species prevalent along with other biting tabanid and muscid flies. The apparent fly densities (flies/trap/day) were significantly higher (p < 0.05) in the late rainy season (1.08, 8.78 and 91 for G. m. submorsitans, tabanids and muscids, respectively) than in the dry season (0.68, 0.35 and 7.33, respectively). The apparent density of G. m. submorsitans was significantly higher (p < 0.05) in the lowland areas than in the midland areas in both the late rainy season and the dry season. A total of 1648 cattle were examined for trypanosomosis with the buffy coat technique and the seasonal prevalence (17.07 and 12.35%, respectively) was significantly (p < 0.05) different. Infection rates were higher (p < 0.05) in the lowland areas, with 19.87 and 17.62%, than in the midland areas, with 13.39 and 6.54%, in the late rainy season and the dry season, respectively. The mean packed cell volume (PCV) values of parasitemic and aparasitemic animals during the late rainy season were 20.7 [plus or minus] 3.5 and 26.6 [plus or minus] 4.3 (p < 0.001), while they were 21.4 [plus or minus] 3.6 and 26.6 [plus or minus] 4.3 (p < 0.001) during the dry season, respectively. The regression analysis indicated that the herd average PCV decreased with the increasing prevalence of trypanosome infections in both seasons.