Evaluation of an antigen detection-ELISA test for the diagnosis of trypanosomiasis in naturally infected cattle.

The sensitivity and the specificity of the antigen detection ELISA proposed by Nantulya and Lindqvist (1989) for the diagnosis of African Animal Trypanosomiasis have been assessed in naturally-occurring infections. 1633 cattle were sampled in trypanosomiasis endemic area and examined for trypanosomes by darkground/phase contrast buffy-coat method described by Murray et al. (1977) and for circulating antigen by ELISA. Fifty sera from Markoye, a tsetse free area in north of Burkina Faso, and 49 sera from Germany were also tested. In trypanosomiasis infested area, BCT detected 144 (8.8%) positive animals while Ag-ELISA revealed 65.8% of positive. Out of the 144 BCT-parasite-positive, Ag-ELISA enable to detect 75% of positive. The predominant trypanosomes identified by BCT was Trypanosoma vivax followed by T. congolense while Ag-ELISA indicated T. congolense followed by T. brucei. Ag-ELISA detected 76.5% out of the 51 T. congolense-BCT-positive and only 17% of all T. vivax BCT-positive. Cattle carring mixed infection involving two or three trypanosomes, particularly those with T. brucei and T. congolense are the most frequent. In tsetse free area, Ag-ELISA detected one positive cattle carring T. brucei and T. congolense and showed an apparent specificity of 98%. No serum from Germany was detected positive. This study suggests the joint use of Ag-ELISA and BCT for the diagnosis of trypanosomiasis particularly in epidemiological study in endemic area.

[Comparison of experimental trypanosomiasis in various breeds of small ruminants in Burkina Faso]. / Comparaison de la trypanosomose expérimentale chez certaines races de petits ruminants au Burkina Faso.

Twenty-four dwarf Djallonké sheep and goats, and 16 Sahelian Fulani sheep and goats, were inoculated with strains of Trypanosoma vivax and Trypanosoma congolense to compare their degree of susceptibility to trypanosomosis. One animal from each breed was used as a control. Anaemia was observed in all inoculated animals. In the group of animals inoculated with T. vivax, 1 Djallonké goat out of 6, 3 Sahelian goats out of 4 and 2 Fulani sheep out of 4 died within the experimental period of 16 weeks. One single Sahelian Fulani sheep out of 4 died among animals inoculated with T. congolense. During a period of 8 weeks, no significant difference was observed between Djallonké and Fulani Sahelian in the decrease of body weight and leucocyte count. Results in this study show a better resistance of Djallonké sheep and goats to infection by T. vivax, whereas there was no significant difference between all sheep and goats inoculated with T. congolense.

[Evaluation of the test for detecting trypanosoma circulating antigens using monoclonal antibodies. Experimental and natural infections]. / Evaluation du test de détection des antigènes circulants de trypanosomes à l'aide d'anticorps monoclonaux. Infections expérimentales et naturelles.

An antigen detection ELISA for the diagnosis of trypanosomes was recently proposed by Nantulya and Lindqvist (1989). Based on species-specific monoclonal antibodies, this test could be used to diagnose a current infection and to identify the causing trypanosomes. The test was evaluated at CRTA during experimental infections in small ruminants and with sera from naturally infected cattle, thanks to reagents supplied by the International Laboratory for Research on Animal Diseases (ILRAD). Sera from cattle sampled in France were also tested. Cattle sera from France gave optical densities (OD) from 0.007 to 0.009 with three monoclonal antibodies against T. congolense, T. vivax and T. brucei. These OD values were well below 0.050, which is considered as a positive threshold OD reading. In the small ruminant experimental infections, the sensitivity of the test was 63.2% for T. congolense-infected animals and 9.9% for T. vivax-infected animals. The sensitivity of parasitological tests was 55.1 and 48.6%, respectively. The combination of the antigen- and parasite-detection tests increased the sensitivity to 82.4 and 52.8%, respectively. Means of OD values, with the naturally infected cattle sera, were 0.116 +/- 0.030 for T. congolense, and 0.011 +/- 0.028 for T. vivax-infected animals. Sixteen out of 20 T. congolense-infected sera (sensitivity of 80%) and one out of 20 T. vivax-infected sera (sensitivity of 5%) gave an OD value exceeding 0.050. The determination of a threshold OD reading lower than 0.050 would greatly improve the sensitivity of the test. This determination could either be done by studying the preinfection sera or a local population of animals living in an area free from trypanosomosis.(ABSTRACT TRUNCATED AT 250 WORDS)