Performance of diagnostic tests for Trypanosoma brucei brucei in experimentally infected pigs

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Résumé

Animal African trypanosomosis is an important vector-borne disease of livestock in sub-
Saharan Africa. Pigs seem relatively tolerant to trypanosome infection and could act as a
reservoir of trypanosomes affecting animals and humans. Our ability to reliably detect trypanosome
infection in pigs depends on the performance of diagnostic tools, which is not
well known. In pigs experimentally infected with Trypanosoma brucei brucei, we evaluated
the performance of parasitological Buffy Coat Technique (BCT), two molecular (TBR and
5.8S PCR) and four serological tests (CATT, HAT Sero-K-Set rapid diagnostic test–RDT,
indirect ELISA, immune trypanolysis). Most diagnostic tests showed high specificity, estimated
at 100% (95% CI = 74–100%) with the exception of CATT and RDT whose specificity
varied between 100% (95% CI = 74–100%) to 50% (95% CI = 7–93%) during the experiment.
The sensitivity of each test fluctuated over the course of the infection. The percentage
of positive BCT over the infection (30%) was lower than of positive PCR (56% and 62%,
depending on primers). Among the serological tests, the percentage of positive tests was
97%, 96%, 86% and 84% for RDT, ELISA, immune trypanolysis and CATT, respectively.
Fair agreement was observed between both molecular tests (κ = 0.36). Among the serological
tests, the agreement between the ELISA and the RDT was substantial (κ = 0.65). Our
results on the T.b. brucei infection model suggest that serological techniques are efficient in
detecting the chronic phase of infection, PCR is able to detect positive samples several
months after parasites inoculation while BCT becomes negative. BCT examination and
RDT are useful to get a quick information in the field, and BCT can be used for treatment
decision. ELISA appears most suited for epidemiological studies. The selection of diagnostic
tests for trypanosomosis in pigs depends on the context, the objectives and the
available resources.

Mots-clés

Trypanosoma brucei, Pig, Diagnosis, Experimental infection