Experimental evidence for pigs as a potential long-term reservoir of Trypanosoma brucei gambiense

Pigs are suspected to act as a reservoir for Trypanosoma brucei gambiense and may therefore contribute to the re-emergence of human African trypanosomiasis (HAT), despite ongoing efforts to eliminate transmission. To clarify the role of this species in HAT epidemiology and to better understand the dynamics of T. b. gambiense infection in blood, we experimentally infected pigs with this parasite. In this study, we compared nine infected pigs with eight control pigs over a period of more than ten months using parasitological, molecular, and serological methods. The results showed that each diagnostic method has limitations, in terms of sensitivity to detect the presence of T. b. gambiense, and specificity to differentiate infection caused by T. b. gambiense from infection caused by T. b. brucei, responsible for animal African trypanosomosis. Nevertheless, the overall analysis showed that pigs can remain infected with T. b. gambiense for at least ten months. Hence, pigs should be considered a potential long-term reservoir of T. b. gambiense that could compromise the sustainability of the current elimination process. As a result, there is a need to pursue investigations on this topic, considering possible co-infections with T. b. brucei. In the meantime, adapted measures should be envisaged to limit contact between pigs and tsetse flies and/or to clear potential pig infections with T. b. gambiense by curative treatment.