Changes

The pathogenesis of BTV infection has been shown to be similar in sheep and cattle, and is assumed to be similar in other species of ruminants^{8, 9, 10}. However, the severity of disease varies greatly with species and cattle in particular express very few signs.  

The pathogenesis of BTV infection has been shown to be similar in sheep and cattle, and is assumed to be similar in other species of ruminants^{8, 9, 10}. However, the severity of disease varies greatly with species and cattle in particular express very few signs.  

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 necrosis¹⁰ 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.

When a BTV-infected midge takes a blood meal from a ruminant host, innoculated virus spreads from the skin to replicate in the regional lymph nodes, tonsils and spleen¹¹. A secondary cell-associated viraemia then 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 necrosis¹⁰ 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.

==Diagnosis==

==Diagnosis==