Revisiting the Immune Trypanolysis Test to Optimise Epidemiological Surveillance and Control of Sleeping Sickness in West Africa

Human African trypanosomiasis (HAT) due to Trypanosoma brucei (T.b.) gambiense is usually diagnosed using two sequential steps: first the card agglutination test for trypanosomiasis (CATT) used for serological screening, followed by parasitological methods to confirm the disease. Currently, CATT will continue to be used as a test for mass screening because of its simplicity and high sensitivity; however, its performance as a tool of surveillance in areas where prevalence is low is poor because of its limited specificity. Hence in the context of HAT elimination, there is a crucial need for a better marker of contact with T.b. gambiense in humans. We evaluated here an existing highly specific serological tool, the trypanolysis test (TL). We evaluated TL in active, latent and historical HAT foci in Guinea, Côte d'Ivoire and Burkina Faso. We found that TL was a marker for exposure to T.b. gambiense. We propose that TL should be used as a surveillance tool to monitor HAT elimination

VAT-specific TL-positive profiles according to study site and HAT status.

<p>Fol/Lor/Bat  =  Folonzo, Loropéni and Batié; nb  =  number; na  =  not available; SUSP, SERO and HAT are defined in the <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000917#s2" target="_blank">Materials and Methods</a> section.</p

Study subjects according to the HAT focus and HAT status.

<p>Fol/Lor/Bat  =  Folonzo, Loropéni and Batié.</p><p>SUSP, SERO and HAT are defined in the <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000917#s2" target="_blank">Materials and Methods</a> section.</p

Control strategies: use of trypanolysis test as a marker of <i>T.b. gambiense</i> transmission.

<p>HAT  =  presence of HAT cases; No HAT  =  absence; SERO  =  presence of subjects with CATT-P end titer ≥1/8 but no parasites detected, No SERO  =  absence; TL+  =  positive in trypanolysis test; TL−  =  negative; * except for a special event, such as population movements, occurs.</p

Results of the medical surveys: sero-prevalence and HAT prevalence.

<p>Fol/Lor/Bat  =  Folonzo, Loropéni and Batié; pos  =  positive.</p><p>CATT-P pos  =  CATT-P end titer ≥1/8.</p

Localisation of sampling areas.

<p>Localisation of sampling areas.</p