Helminth immunity and vaccines in sheep

Vaccination of domestic animal species against various parasitic helminths using attenuated parasites or nonliving parasitic material is possible. Improved prospects for vaccines composed of somatic and metabolic parasite components hinge on the isolation and characterization of helminth protective antigens and their synthesis by modern bioengineering techniques. Vaccination strategies beg an understanding of the host's immune effector mechanisms for their most efficient prolonged stimulation. Parameters of importance are antigen dose, frequency of and interval between doses, use of liposomes or other antigen delivery vehicles, and the use and choice of adjuvants.