The role of lectins and trypanosome genotype in the maturation of midgut infections in Glossina morsitans.

Feeding D + Glucosamine to Glossina morsitans throughout their life significantly reduced the proportions of midgut infections which developed into mature infections with three different stocks of Trypanosoma congolense. In one stock of T. congolense, maturation was completely blocked by this carbohydrate, which is known to specifically inhibit tsetse midgut lectin activity. Similar experiments with T. brucei showed that D + Glucosamine also inhibited maturation and, when combined with results from previous experiments with the same carbohydrate, indicated that lectin inhibition also had significant effects on T. brucei infections. It is concluded that midgut lectin secreted by the fly is responsible for triggering maturation of procyclic T. congolense and T. brucei. The maturation response of midgut trypanosomes to lectin stimulation varies between species and between stocks of the same trypanosome species, probably reflecting differences in numbers of lectin binding sites which are determined by trypanosome genotypes.