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Bluetongue Virus (view source)

Revision as of 17:43, 20 August 2010

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When a BTV-infected midge takes a blood meal from a ruminant host, innoculated virus spreads from the skin to the regional lymph nodes. After initial replication in the lymph nodes, a cell-associated viraemia carries the virus to many tissues where further replication occurs in macrophages and endothelial cells. In the process of reproducing, bluetongue virus causes endothelial cell injury and necrosis9 which can increase vascular permeability to cause oedema. Endothelial damage can also give thrombosis, leading to tissue infarction. In sheep and deer a consumptive coagulopathy may occur2.

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As ''Culicoides'' midges are biological vectors of BTV, the virus replicates in insect tissue after feeding on an infected host10. Vector insects can only transmit BTV to another susceptible ruminant after an extrinsic incubation period of some 10 - 14 days, during which time the virus is disseminated from the insect's gut to its salivary glands. The external incubation period is shorter when insects are held at high ambient temperatures. Vertical transmission with transovarial transfer of BTV has not been demonstrated in Culicoides insects, however, infection of adult insects is lifelong. Furthermore, individual insects can survive for relatively long periods of time, particularly in cooler ambient temperatures [23].

==Diagnosis==

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