Abstract
Although the elimination of human African trypanosomiasis (HAT) as a public health problem can be considered as achieved in some foci, the interruption of its transmission by 2030 remains a challenge due to the presence of hidden trypanosome reservoirs such as the animal reservoir and the cutaneous reservoir. In addition, to fight against HAT, vector control (LAV) has been implemented in the Campo HAT focus with a view to reducing contact between the tsetse fly and its hosts. However, the effect of this control on trypanosome transmission in this focus remains unknown. Our study aims to improve the control of African trypanosomiasis by generating data on hidden reservoirs of trypanosomes in mammalian hosts of HAT foci in Cameroon before and after vector control.During medical surveys carried out from October 2019 to April 2022 in the Campo and Bipindi foci, the population was screened using the card agglutination test for trypanosomiasis (CATT) on whole blood and then on diluted plasma. Parasitological tests were performed in individuals with a CATT dilution on plasma ≥ 1/4. In all individuals with enlarged lymph nodes, an aspiration was examined microscopically. Our population was classified as control, serologically suspect and HAT cases. In these individuals, a clinical and dermatological questionnaire was conducted, and 5mL of blood and two skin biopsies were collected. In parallel, 5mL of blood and two skin biopsies were collected from domestic and wild animals in these localities. In the laboratory, DNA was extracted from blood dried on Whatman paper and from a skin biopsy, followed by molecular identification of the different trypanosome species. The second biopsy was used for immunohistochemical analysis.A total of 291 animals were sampled before vector control, including 275 (94.5%) domestic animals and 16 (5.5%) wild animals. PCR revealed 137 animals (47.1%) harboring at least one species of trypanosome in the blood and/or skin. Of the 137 infected animals, 90 (65.7%) and 32 (23.4%) had trypanosomes in blood and skin respectively. Fifteen (10.9%) animals had trypanosome infections in both blood and skin. Trypanosoma brucei gambiense (T. b. gambiense) infections were detected in the blood of 7.6% (22/291) of animals. Of 131 animal samples analyzed two years after LAV, 39 (29.8%) animals were CATT positive and 37 (28.2%) harbored at least one trypanosome species or subspecies in the blood. Comparing infection rates before and after two years of LAV, a significant reduction was observed (X2=19.32; P<0.0001).In Human, 95 individuals, including 5 HAT cases, 22 serological suspects and 66 controls, were included in the study. T. b. gambiense infections were found in the blood and skin of 8 (8.6%) and 37 (39.8%) individuals respectively. Immunohistochemical analysis confirmed the presence of trypanosomes in the dermis of 28 (30.1%) individuals, including 2 trypanosomal, 5 serological suspects and 21 controls.This study revealed the presence of T. b. gambiense, a human pathogenic parasite in various animal taxa, as well as dermal trypanosomes in both humans and animals. Vector control is very effective in interrupting trypanosome transmission in the Campo HAT focus. The results of this study suggest the need to consider not only animal and dermal reservoirs, but also to continue with vector control in the development of control strategies aimed at interrupting trypanosome transmission.