Is there a vaccine against trypanosomiasis?
Despite much research, no vaccine to prevent trypanosomiasis in animals or humans has been developed, and the prospects of developing one are very poor. The reason for this is that trypanosomes have evolved a system to evade the host’s immune system by varying the structure of their surface coating (Vickerman, 1978). This change is controlled genetically and each parasite has a huge so-called ‘repertoire’ of variable antigenic type (VATs). As the host’s immune system responds to one VAT, the parasite switches to another and thereby evades destruction. Within any particular geographical area, there will be several species, subspecies, types and strains of trypanosome, each with its own repertoire of VATs. Consequently, livestock cannot develop an effective immunity to the disease.
Vickerman, K. (1978). Antigenic variation in trypanosomes. Nature 273, 613-617.