Transmission of trypanosomiasis by tsetse flies in three active HAT foci of the Republic of Congo

Abstract

Abstract Introduction: Human African Trypanosomiasis (HAT) is a neglected tropical disease still endemic in the Republic of Congo. Despite continuous detection of HAT cases in the country, there is still not enough data on trypanosome infections in tsetse flies, trypanosome species and tsetse flies species distribution in endemic foci. The present study is intended to fill this gap and improve understanding on trypanosome circulation in three active foci in the centre and south of Congo.Methods: Pyramid traps were set in various places in villages to collect tsetse flies both during rainy and dry season. Once collected, tsetse flies were identified using morphological keys. DNA extracted from flies was processed by PCR for species identification and for detection of trypanosome. A second PCR was ran for different trypanosome species identification.Results: A total of 1291 tsetse flies were collected. The average apparent density of fly per day was 0.043 in Mpouya, 0.73 in Ngabé and 2.79 in Loudima. Glossina fuscipes quazensis was the predominant tsetse fly found in Ngabé and Mpouya, while Glossina palpalis palpalis was the only tsetse fly found in Loudima. A total of 224 (17.7%) flies were detected infected by trypanosomes; 100 (7.91%) by Trypanosoma congolense savannah, 22 (1.74%) by Trypanosoma congolense forest, 15 (1.19%) by Trypanosoma vivax, 83 (6.56%) by Trypanosoma brucei (s.l.) and 2 (0.16%) undetermined species. A total of 57 co-infections between T. brucei (s.l.) and T. congolense savannah or T. brucei (s.l.) and T. congolense forest were found only in G. p. palpalis. Loudima recorded the highest number of infected tsetse flies.Conclusion: The study provided updated information on the dynamics of tsetse fly populations as well as on the transmission of trypanosome species in the different active HAT foci in Congo. The data suggest high transmission of animal trypanosomes and possibly human trypanosomes in these foci. The study stress the need for active surveillance in these endemic foci.