Abstract
BackgroundBecause of its high sensitivity and its ease of use in the field, the card agglutination test for trypanosomiasis (CATT) is widely used for mass screening of sleeping sickness. However, the CATT exhibits false-positive results (i) raising the question of whether CATT-positive subjects who are negative in parasitology are truly exposed to infection and (ii) making it difficult to evaluate whether Trypanosoma brucei (T.b.) gambiense is still circulating in areas of low endemicity. The objective of this study was to assess the value of the immune trypanolysis test (TL) in characterising the HAT status of CATT-positive subjects and to monitor HAT elimination in West Africa.Methodology/Principal FindingsTL was performed on plasma collected from CATT-positive persons identified within medical surveys in several West African HAT foci in Guinea, Côte d'Ivoire and Burkina Faso with diverse epidemiological statuses (active, latent, or historical). All HAT cases were TL+. All subjects living in a nonendemic area were TL−. CATT prevalence was not correlated with HAT prevalence in the study areas, whereas a significant correlation was found using TL.Conclusion and SignificanceTL appears to be a marker for contact with T.b. gambiense. TL can be a tool (i) at an individual level to identify nonparasitologically confirmed CATT-positive subjects as well as those who had contact with T.b. gambiense and should be followed up, (ii) at a population level to identify priority areas for intervention, and (iii) in the context of HAT elimination to identify areas free of HAT.
Highlights
Human African trypanosomiasis (HAT) or sleeping sickness is caused by two subspecies of the protozoan flagellate Trypanosoma brucei
The objective of the present study was to evaluate the use of TL with T.b. gambiense variable antigen type (VAT) LiTat 1.3, LiTat 1.5 and LiTat 1.6 aiming at improved epidemiological surveillance of sleeping sickness in West Africa, with special interest in card agglutination test for trypanosomiasis (CATT)-seropositive persons
Our results argue that TL could be used (i) as a tool to identify CATT-positive subjects who experienced contact with T.b. gambiense and (ii) as a surveillance tool to monitor HAT elimination
Summary
Human African trypanosomiasis (HAT) or sleeping sickness is caused by two subspecies of the protozoan flagellate Trypanosoma brucei. After the successful control campaigns dating from 1930 to 1960, T.b. gambiense sleeping sickness re-emerged in the 1980s, with tens of thousands of cases treated every year. As a result of control activities, reported cases decreased to a mere 11,382 patients in 2006 [2] and to less than the symbolic number of 10,000 in 2009. In Cote d’Ivoire, control activities since the 1980s [6] have resulted in a low disease prevalence with a few tens of HAT cases annually, mainly from the Central West foci. The CATT exhibits false-positive results (i) raising the question of whether CATT-positive subjects who are negative in parasitology are truly exposed to infection and (ii) making it difficult to evaluate whether Trypanosoma brucei (T.b.) gambiense is still circulating in areas of low endemicity. The objective of this study was to assess the value of the immune trypanolysis test (TL) in characterising the HAT status of CATT-positive subjects and to monitor HAT elimination in West Africa
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