Impact of vector control on the prevalence of pathogenic trypanosomes circulating in domestic animals in the Campo sleeping sickness focus of Southern Cameroon.

Vector control (VC) using Tiny Targets was implemented in the Campo human African trypanosomiasis (HAT) focus in Cameroon from January 2020 to January 2022, where HAT cases continue to be reported annually. Because human and animal African trypanosomiasis (AAT) share the same tsetse fly vector and trypanosome species circulate sympatrically, this study assessed the impact of VC on trypanosome transmission in domestic animals. Blood samples were collected from pigs, goats, sheep, and dogs in 2019 (pre-intervention), 2022, and 2023 (post-intervention). The Card Agglutination Test for Trypanosomiasis (CATT) was used to detect anti-trypanosomal antibodies, while molecular tools were used to identify each trypanosome species and subspecies. A total of 311 animals were sampled (101 in 2019, 131 in 2022, and 79 in 2023). Overall CATT seroprevalence declined significantly from 39.6% in 2019 to22.8% in 2023 (χ²= 4.19, P = 0.041). Similarly, PCR-confirmed trypanosome infections decreased from 47.5% to 29.1%. Before VC, Trypanosoma brucei s.l., T. vivax, and T. congolense forest and savannah types were detected, whereas only T. brucei s.l. and T. congolense forest type were detected after VC. Vector control substantially reduced trypanosome transmission in domestic animals, as reflected by lower seroprevalence and infection rates. Importantly, although T. b. gambiense infections were detected before VC, none were detected following the intervention in animals or tsetse flies. These findings support sustained and expanded VC as a component of an integrated One Health strategy to interrupt trypanosome transmission and accelerate the elimination of HAT and reduce the burden of AAT.