Division of Virology, Indian Veterinary Research Institute, Mukteswar-263138, India.
Bluetongue (BT) is a non-contagious, arthropod-borne viral disease of both domestic and wild ruminants caused by bluetongue virus (BTV). The disease is enzootic in some areas with cattle and other wild ruminants serving as reservoirs for the virus. After the establishment of BT, it is impossible to actively eradicate BTV as the virus circulates subclinically in cattle, other ruminants and in midges. Presently, 24 serotypes (possibly 25) of BTV have been recognized worldwide, with 21 serotypes prevailing in India. The major control measures include restriction of animal movement, vector control using insecticides/larvicides, slaughter of infected animals and vaccination. Prophylactic immunization of sheep against bluetongue is the most practical and effective control measure to combat bluetongue infection, especially when the threat is from an epizootic due to a single or multiple serotypes. Multivalent vaccines have drawbacks of interference between virus strains, differences in immunogenicity and growth rates between strains, as well as differences in the response of individual animals to the individual components of such vaccines. However, South African scientists developed BT vaccine during 1940, to combat then prevalent 15 different BTV serotypes. Currently, Onderstepoort Biological Products (OBP) is the only producer of commercial live attenuated bluetongue vaccine globally for domestic/export purposes. The merits and demerits of the widely used conventional and modern bluetongue vaccines viz., inactivated, live attenuated, recombinant and oral vaccines will be discussed.
