Relatively simple protocols employing non-radioactive DNA probes have been used for the detection of African trypanosomes in the blood of mammalian hosts and the saliva of live tsetse flies. In combination with the polymerase chain reaction (PCR), the protocols revealed trypanosomes in buffy-coat samples from antigenaemic but aparasitaemic cattle and in the saliva of live, infected tsetse flies. Furthermore, the protocols were used to demonstrate concurrent natural infections of single tsetse flies with different species of African trypanosomes.

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The characterization of four Trypanosoma vivax isolates from Colombia in South America showed that although minor phenotypic differences existed between them, these parasites are antigenically related and belong to a single serodeme. Characterization by isoenzyme assay, karyotyping and DNA probe analysis, showed the Colombian isolates to be more similar to the West African than to Kenyan T. vivax. There was, however, little serological cross-reactivity between South American and African groups of T. vivax. Although the T. vivax isolates from Colombia were pathogenic for dairy calves which showed the typical sign of progressive emaciation, these parasites failed to infect mice or tsetse and could not be cultivated as bloodstream forms in vitro. This study represents initial attempts to establish the phenotypic and serological diversity amongst T. vivax isolates from South America.

Antigenic variation in the ILDar 1 serodeme of the naturally rodent-infective stock of West African Trypanosoma vivax has been investigated following cyclical transmission. The immunofluorescent and immune lysis tests were employed with a panel of 39 variant-specific mouse antisera. When antigenically homogeneous, or mixed, populations were transmitted by tsetse flies to goats, the first peak parasitaemias arising in the goats were antigenic mixtures (up to 9 major, and several minor variants being recognized in some cases) from which the ingested variant was absent. Although first peak parasitaemias in similarly infected goats showed some variants in common, there was no obvious relationship between the VAT profiles in different goats. When these populations were expanded in irradiated mice, VAT heterogeneity was maintained with a tendency towards the development of predominant variants in some, but not all, instances. Six additional variants, derived following the growth of bloodstream form ILDat 1.9 in 37 degrees C culture, were also represented in goat and mouse populations. Two further variants, isolated after cyclical development of ILDat 1.9-derived trypanosomes in vitro, were not present in the early parasitaemias in goats and mice.