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===Vectors===

===Vectors===

The arthropod vector for bluetongue virus is the ''Culicoides'' biting midge. These insects take blood meals from vertebrate hosts and breed in damp, dung-enriched soil enriched, and so are abdunant in the vicinity of domestic livestock. Once eggs are laid in soil, ''Culicoides'' progresses through four larval stages and pupates before becoming an adult midge. The lifecycle is greatly influenced by temperature: in temperate regions such as Britain, the adult midge population declines in October and is absent by December. The fourth larval stage overwinters, and adults re-appear the following April. The environment affects the activity of adult midges in a variety of ways. ''Culicoides'' survive around 10 days in warm weather but up to one month when conditions are cooler and are most active at night, from an hour before sunset to an hour after sunrise. Activity is decreased by windy conditions, and increased during the day when the weather is dull. Bluetongue virus replicates more rapidly in vector species when temperatures are warmer.  

The arthropod vector for bluetongue virus is the ''Culicoides'' biting midge. These are biological vectors of BTV, so the virus replicates in insect tissue after feeding on an infected host¹⁰.  It takes 10-14 days for the virus to dissminated from the insect's gut to its salivary glands, after which bluetongue virus may be transmitted to a new, susceptible ruminant host. This incubation period may be reduced when ambient temperatures are higher², and midges maintaine a life-long infection.

 

These insects take blood meals from vertebrate hosts and breed in damp, dung-enriched soil enriched, and so are abdunant in the vicinity of domestic livestock. Once eggs are laid in soil, ''Culicoides'' progresses through four larval stages and pupates before becoming an adult midge. The lifecycle is greatly influenced by temperature: in temperate regions such as Britain, the adult midge population declines in October and is absent by December. The fourth larval stage overwinters, and adults re-appear the following April. The environment affects the activity of adult midges in a variety of ways. ''Culicoides'' survive around 10 days in warm weather but up to one month when conditions are cooler and are most active at night, from an hour before sunset to an hour after sunrise. Activity is decreased by windy conditions, and increased during the day when the weather is dull. Bluetongue virus replicates more rapidly in vector species when temperatures are warmer.  

 

Classically, the major vector for BTV is ''Culicoides imicola''. This midge is found throughout Africa, the

Classically, the major vector for BTV is ''Culicoides imicola''. This midge is found throughout Africa, the