Bovine trypanosomosis, vector distribution and infection rate in three districts of Gamo Zone, southwestern Ethiopia

African animal trypanosomosis is one of the main obstacles to the development of livestock and agricultural output in Ethiopia. It usually results in a severe, frequently fatal sickness, and the infected animals were more weakened as the disease progress and become unfit for work. A cross sectional study design was conducted from December 2021 to April 2022 with the aim of estimating the prevalence of trypanosome infection both in <i>Glossina</i> spp. and cattle, and to assess apparent density of <i>Glossina</i> spp. A total of 298 cattle were selected and examined for trypanosome by using buffy coat technique. The overall prevalence of bovine trypanosomosis was 19.1%; and two species of trypanosomes, <i>T. congolense</i> and <i>T. vivax</i>, were identified in the study area. The prevalence of <i>T</i>. <i>congolense</i> and <i>T. vivax</i> were 15.8% and 2.3%, respectively. The prevalence of trypanosomosis was significantly higher in adult animals (OR = 2.7; <i>p</i> < 0.05) than in younger cattle and poor body condition (OR = 3.18; p <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo><</mml:mo></mml:math> 0.05) than medium body condition animals. The mean PCV value of infected animals was 14.3% (13.3-15.4) significantly lower than the non-infected animals 18.5% (17.8-19.2). <i>Glossina pallidipes</i> is the only tsetse species encountered in all the study areas. In total, 2992 flies were caught of which 90.8% belong to <i>G. pallidipes</i> and 9.2% were other biting flies. The overall apparent density of <i>G. pallidipes</i> was 20.1 F/T/D and other biting flies were 2.0 F/T/D. A total of 307 live <i>Glossina pallidipes</i> were dissected. The overall prevalence of <i>Glossina pallidipes</i> infection rate was 9.1% (95% CI = 5.9-12.4). The prevalence of <i>G. pallidipes</i> infection was significantly higher in Kucha district (OR = 3.2, χ² = 2.6, p <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo><</mml:mo></mml:math> 0.05) than the other two districts, Daramalo and Arba Minch Zuria. Also it was significantly higher in flies trapped from riverine forest areas (OR = 5.5, χ² = 2.86, p <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo><</mml:mo></mml:math> 0.05). Therefore, to reduce the impact of trypanosomosis and <i>Glossina,</i> vector control and treating infected cattle with prophylactic or chemotherapeutic drugs and active community participation can play a key role.