Bluetongue virus outbreak in Tamil Nadu, southern India: Need to study the Indian biting midge vectors, Culicoides Latreille (Diptera: Ceratopogonidae)

Bluetongue (BT) is a viral disease causing morbidity and mortality in sheep, cattle and wild ruminants, including deer, sambar and bluebull. BT is endemic in many parts of India and its outbreak in Tamil Nadu during the monsoon season of 1997–98 caused the death of 300,000 sheep and goats. However, the extent of damage to the wild ruminants remains unknown. Current research for controlling BT is confined to the development of vaccines in disease vulnerable states, with which complete success is questionable because of the presence of more than 20 serotypes of the virus. Vector control through integrated, intensive management is feasible, but there is little knowledge of the biting midges, Culicoides Latreille (Diptera: Ceratopogonidae) in southern India. Culicoides brevitasis Keiffer and C. imicola Keiffer are proven vectors of BT virus, occurring widely in India and other parts of the Oriental region. There is an urgent need to study Culicoides sp. intraspecies variation and genetic variation because of the recent BT disease outbreak. This information will provide an understanding about BT transmission and control and vector competence of Culicoides in India. This article presents the first report of BT in Tamil Nadu over the past 12 years (1988–99), reviews the current knowledge of Indian Culicoides fauna, and how the lack of understanding of taxonomy, biology and behaviour of this fauna affects effective vector control measures.