Bluetongue vaccines.

Once thought largely restricted to India and Africa, the insect-borne livestock pathogen Bluetongue virus is now present on every continent with the exception of Antarctica. Outbreaks of the disease caused by the virus in Europe over the last decade, and the resulting impact on trade and agriculture, have focussed attention on the production of safe and effective vaccines. The determinants of protection for bluetongue are well defined but the variability of the virus, which exists as 24 immunologically distinct serotypes, means that even regions where large numbers of animals have been vaccinated remain at risk from new outbreaks of the virus.