Prospects for the Development of Dead Vaccines against Helminths

Parasitic helminths rarely cause acute disease with high mortality in either man or livestock. A disease caused by the presence of helminths is likely to produce a chronic debilitating condition in which symptoms develop gradually. An important feature of most helminth diseases is the long persistence of some adult parasites in hosts, which have acquired high levels of resistance to new infections. Evasion of the immune effector mechanisms by some of the parasites derived from a primary infection tends to obscure the development of resistance to reinfection. The first attempts to vaccinate against parasitic helminths with dead whole organisms or extracts were made in the 1930s and although a few results seem to have been promising enough to warrant further investigation, most were rather disappointing and interest waned until the 1950s. The chapter describes the empirical approach to the development of dead vaccines, which has had a chequered history but shows some current promise of success. It also addresses some problems yet to be solved before experimental vaccination can be translated from the laboratory to actual production.