Molecular vaccines against animal parasites.

Vaccines against parasites have been significantly more difficult to develop than vaccines for other infectious agents. However much has been published within the very recent past which indicates that it is not only possible to induce protective immune responses to a broad range of parasites of veterinary importance with subunit materials but it appears that cross-isolate and cross-species immunogens may be obtainable. Advances in molecular immunology now provide technical approaches to vaccine design which directly address the question of improving the immunogenicity of parasite vaccines and the very wide potential range of prospective live vectors for recombinant vaccine antigens help to ensure the availability of practical commercial vaccine vectors for the future. From the technical-scientific aspect therefore the feasibility for developing molecular parasite vaccines for animal health is sound. On the commercial side, the need to keep discovering novel and effective parasiticidal drugs because of resistance development presents a major financial and research burden. Growing concerns on drug residues and environmental issues mitigates in favour of controlling parasitic diseases by biological methods among which vaccines would appear to be pre-eminently suitable. It is conceivable that we are now coming to the end of the era in which animal parasites are controlled very well by prophylactic chemotherapy and slowly moving into an era where vaccination will prevail. The deployment of molecular parasite vaccines in animal health can be envisaged within five years.