Absence of serological markers of infection with Trypanosoma brucei gambiense in domestic animals in a sleeping sickness focus in south Congo.

A total of 33 domestic animals living in close contact with man in a human trypanosomiasis focus in South Congo were examined parasitologically and tested for serological markers of Trypanosoma brucei gambiense infection. 84.8% of the animals presented detectable T. congolense parasitaemia. The high rate of seropositivity observed with CATT (81.8%) contrasted with the low seroprevalence found with ELISA (less than 13%). None of the 33 plasma samples showed lytic antibodies when analysed by immune lysis test against 10 distinct T. b. gambiense predominant variable antigen types (LiTat 1.1 to 1.10). The results demonstrate the lack of specificity of CATT, and to a lesser extent ELISA, in detecting T. b. gambiense infection in animals. The seropositivity may be due to cross-reaction with certain T. congolense antigens. The absence of serological markers specific to T. b. gambiense confirms the parasitological data which estimate the prevalence rate of animals infected with Trypanozoon as less than 1% in the region.