A comparison of skin-test responses using antigen from Leishmania donovani and a lizard trypanosome

261 individuals were skin tested with leishmanin from Leishmania donovani and with an antigen from a lizard trypanosome isolated in an area endemic for kala-azar in Ethiopia. 83 of the 261 responded positively, with indurations of 5 mm or greater, to one antigen but negatively to the other, and 42 reacted positively to both. Among the Afar people of the Awash valley in north-eastern Ethiopia and the Nyangatom people of south-western Ethiopia, positive response to both antigens was high, though many individuals responded to one antigen but not the other. Both these groups live as cattle pasturalists, a predominantly male occupation, in areas where known vectors of kala-azar as well as lizard-feeding sandflies exist. Among the Anuak and Suri people, who live in areas of south-western Ethiopia infested with tsetse flies, the lizard trypanosome antigen gave a markedly higher skin test positivity than did the leishmanin antigen. This suggests that the lizard trypanosome may give artificially high results in other immunological tests of exposure to trypanosomiasis in areas where lizard trypanosomes and man-biting sandflies co-exist with mammalian trypanosomes transmitted by Glossina.