High Trypanosome Infection Rate and Blood-Feeding Patterns of Tsetse Flies in South Ethiopia

Abstract Background Tsetse control has been implemented for decades using various methods. However, the impact of these interventions on tsetse infection rates remains unclear, highlighting the need for more comprehensive data on trypanosome infection rates and tsetse feeding patterns. This study aimed to assess trypanosome infection rates and feeding patterns in tsetse flies collected with different attractants in south Ethiopia. Materials and Methods The study was conducted in the Deme River Valley, Gamo Zone, South Ethiopia. Each month, sampling was conducted over two consecutive days at each site using 10 NGU traps, with trap locations rotated. Traps were baited with acetone, fermented cow urine, both, or left unbaited as controls. Anesthetized and recently deceased tsetse flies were examined for infections using microscopy, while the sources of their blood meals were analyzed using multiplex polymerase chain reaction (PCR). We used the Poisson regression model to analyse count data and the binary logistic regression model to assess binary outcomes (positive or negative) and infection rates. Results Of the 1208 tsetse flies captured, 751 (62.2%) were Glossina pallidipes , while 457 (37.8%) were Glossina fuscipes fuscipes . The overall trypanosome infection rate in the tsetse flies was 17.1% (103/603) (95% CI: 14.2–20.3). Out of the 103 flies that tested positive through microscopy, 66% were found to be infected with Trypanosoma congolense , 24.3% with Trypanosoma vivax , 1.9% with Trypanosoma brucei , and 7.8% with either T. congolense or T. brucei . The infection rate of trypanosomes in G. pallidipes was 19.6%, while it was 12.8% in G. f. fuscipes . Traps using a combination of cow urine and acetone captured more trypanosome-positive tsetse flies (21.2%), followed by acetone alone (18.9%), cow urine alone (12.2%), and traps without odour bait (6.1%). Of 107 freshly fed tsetse flies tested using multiplex polymerase chain reaction, 23.4% had fed on dogs, 8.4% on humans, 7.5% on cattle, and 4.7% on goats, including mixed blood meals. Conclusions The high trypanosome infection rate in tsetse flies suggests an increased risk of parasite transmission. The blood meal sources highlight the potential risk to humans. More research is needed to clarify the role of dogs in the transmission of parasites.