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. 2017 Nov 3;10(1):546.
doi: 10.1186/s13071-017-2487-8.

Serological tests for gambiense human African trypanosomiasis detect antibodies in cattle

Enock Matovu  1 , Annah Kitibwa  2 , Albert Picado  3 , Sylvain Biéler  3 , Paul R Bessell  4 , Joseph Mathu Ndung'u  3
Affiliations

Serological tests for gambiense human African trypanosomiasis detect antibodies in cattle

Enock Matovu et al. Parasit Vectors. .

Abstract

Background: Serological tests for gambiense human African trypanosomiasis (gHAT) detect antibodies to antigens on the cell surface of bloodstream trypanosomes. As trypanosomes that cause animal African trypanosomiasis (AAT) also express related antigens, we have evaluated two rapid diagnostic tests (RDTs) on cattle in trypanosomiasis endemic and non-endemic regions, to determine whether gHAT serological tests could also be used to screen for AAT.

Methods: Two RDTs, 1G RDT, made with native antigens, and p2G RDT, made with recombinant antigens, were tested on 121 cattle in a trypanosomiasis-free region, and on 312 cattle from a rhodesiense HAT and AAT endemic region. A subset of samples from the endemic region were also tested with two immune trypanolysis (TL) tests. The sensitivity of the tests was estimated by evaluating the result of the RDT on samples that were positive by both microscopy and internal transcribed spacer (ITS) PCR, whilst specificity was the result of the RDT on samples that were negative by ITS PCR and microscopy, and others from the non-endemic region.

Results: The specificity of the p2G RDT on cattle from the non-endemic region was 97.5% (95% CI: 93.0-99.2%), compared to only 57.9% (95% CI: 48.9-66.3%) for 1G RDT. The specificities of 1G RDT, p2G RDT and TL on endemic control cattle were 14.6% (95% CI: 9.7-21.5%), 22.6% (95% CI: 16.4-30.3%) and 68.3% (95% CI: 59.6-75.9%), respectively. The sensitivities of the tests on trypanosome positive samples were 85.1% (95% CI: 79.1-89.7%), 89.1% (95% CI: 83.7-93.0%) and 59.3% (95% CI: 51.8-66.4%), respectively. Among the same samples, 51.7% were positive by both TL and the 1G RDT.

Conclusions: These serological tests detect cross-reacting antibodies in cattle. The p2G RDT based on recombinant antigens had a high specificity in a non-endemic region, while the 1G RDT had a lower specificity, suggesting cross-reactivity with other pathogens.

Keywords: Invariant surface glycoproteins; Serological tests; Specificity; Trypanosomes; Variant surface glycoproteins.

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Conflict of interest statement

Ethics approval and consent to participate

Consent to take samples from cattle was given verbally by the owners.

Consent for publication

Not applicable.

Competing interests

AP, JMN and SB are employees of FIND, which co-developed the RDTs used in the present study. PB is a consultant for FIND. The authors declare no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Map of Kenya and Uganda showing the counties of origin of samples analysed (Ugandan samples are shown in red, Kenyan Samples in green). The geographical layers were obtained from CC-BY License compatible sources: GADM (http://www.gadm.org) and the RCMRD geoportal (http://geoportal.rcmrd.org/)
Fig. 2
Fig. 2
A 1G RDT for gHAT (a) and colour chart (b) for estimating the intensity of positive results. The RDT shows positive results on both antigen bands (1 and 2) after testing fresh blood. C, control band
Fig. 3
Fig. 3
Percentage and 95% confidence interval of samples found positive with 1G RDT in cattle in a non-endemic region of Kenya. The results are shown by age group, overall RDT result and individual bands
See this image and copyright information in PMC

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