title: Towards a new reference test for surra in camels.
abstract: Current serological diagnosis of Trypanosoma evansi infection in camels is based on the native variable antigen type RoTat 1.2. The goal of this study was to develop a novel serological diagnostic test based on a nonvariable protein and freed from the use of rats or mice for its production. An enzyme-linked immunosorbent assay using a recombinant extracellular domain of invariant surface glycoprotein 75 (ELISA/rISG75) was developed and tested on a collection of 184 camel sera. The results were compared to those obtained from three established antibody detection tests based on variable surface glycoprotein RoTat 1.2: an ELISA for T. evansi (ELISA/T. evansi), a card agglutination test for trypanosomiasis (CATT/T. evansi), and an immune trypanolysis (TL) assay. The ELISA/rISG75 and the ELISA/T. evansi showed a sensitivity of 94.6% (95% confidence interval [CI], 87.8 to 98.2%, at 19% positivity cutoff value) and 98.9% (95% CI, 94.1 to 99.8, at 12% positivity cutoff value), respectively. The ELISA/rISG75 had 100% specificity (CI, 95.9 to 100%), while the ELISA/T. evansi showed 98.9% specificity (CI, 95.9 to 100%). The ELISA/rISG75 demonstrated an almost perfect agreement with the TL assay, the CATT/T. evansi, and the ELISA/T. evansi, with kappa scores of at least 0.94. The ELISA/rISG75, having a performance comparable to that of the gold standard (the TL assay) and being independent of antigenic variation, may become a new reference test for surra in camels. It opens avenues for the diagnosis of T. evansi infections in other hosts as well as for the development of a pan-Trypanozoon test for detection of Trypanosoma brucei brucei, T. b. gambiense, T. b. rhodesiense, T. evansi, and T. equiperdum.
authors.affiliation: Department of Parasitology, Institute of Tropical Medicine, Antwerp, Belgium. thao.tran@vub.ac.be
authors.forename: Thao
authors.initials: T
authors.lastname: Tran
authors.forename: Filip
authors.initials: F
authors.lastname: Claes
authors.forename: Didier
authors.initials: D
authors.lastname: Verloo
authors.forename: Henri
authors.initials: H
authors.lastname: De Greve
authors.forename: Philippe
authors.initials: P
authors.lastname: Büscher
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D000953:Antigens, Protozoan; D002162:Camelus / Q000469:parasitology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D011994:Recombinant Proteins; D012680:Sensitivity and Specificity; D014345:Trypanosoma / Q000276:immunology*; D014352:Trypanosomiasis / Q000175:diagnosis / Q000662:veterinary*
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D011994:Recombinant Proteins