Effective
vaccines are available for many protozoal diseases of animals, including
vaccines for zoonotic pathogens and for several species of vector-transmitted apicomplexan haemoparasites. In comparison with human diseases,
vaccine development for animals has practical advantages such as the ability to perform experiments in the natural host, the option to manufacture some
vaccines in vivo, and lower safety requirements. Although it is proper for human
vaccines to be held to higher standards, the enduring lack of
vaccines for human protozoal diseases is difficult to reconcile with the comparatively immense amount of research funding. Common tactical problems of human protozoal
vaccine research include reliance upon adapted rather than natural
animal disease models, and an overwhelming emphasis on novel approaches that are usually attempted in replacement of rather than for improvement upon the types of designs used in effective veterinary
vaccines. Currently, all effective protozoal
vaccines for animals are predicated upon the ability to grow protozoal organisms. Because human protozoal
vaccines need to be as effective as animal
vaccines, researchers should benefit from a comparison of existing veterinary products and leading experimental
vaccine designs. With this in mind, protozoal
vaccines are here reviewed.