Tsetse immunity and the transmission of trypanosomiasis.

Cyclical transmission of African trypanosomes - Trypanosoma congolense and subspecies of T. brucei - depends on their uptake by and development within their tsetse fly vectors. Tsetse susceptibility to such trypanosome infection seems to be controlled by maternally inherited rickettsia-like organisms (RLOs) (Fig. 1) and it now seems that the RLOs may exert this effect by controlling midgut lectins in the fly. Ian Maudlin and Susan Welburn explain the latest findings.