Changes

===Vectors===

===Vectors===

The arthropd 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. ''Culicoides'' generally avoid entering buildings and other closed spaces.

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. ''Culicoides'' generally avoid entering buildings and other closed spaces.

3.4 Culicoides imicola is the major vector of BTV in the Old World. It is one of the

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

most widely distributed of Culicoides species. It occurs throughout most of Africa, the

Middle East, southern Asia, Portugal, Greece, Corsica, Sardinia, Sicily and areas of Italy¹, and its distribution appears to be extending northwards. However, ''C. imicola'' has not yet been demonstrated in the United Kingdom. The ''Culicoides'' species found in the British Isles are ''C. pulicais'' and ''C. obsoletus'', which are also common across central and northern Europe. Knowledge of the distribution of these species in the UK is incomplete, but in general the insects gather where breeding sites and hosts occur in tandem.  

Middle East, southern Asia, much of Portugal, south-west Spain and the Balearics,

many Greek Islands, substantial parts of the Greek mainland, Corsica, Sardinia, Sicily

and wide areas of southern and central mainland Italy.

C. imicola appears to be expanding its range both northwards and westwards but is

still restricted in Europe to southern parts. C. imicola has not been recorded in Great

Britain.

3.5 Culicoides obsoletus is probably one of the commonest Culicoides species

across the whole of central and northern Europe. Similarly, C. pulicaris is also

common throughout central and northern Europe. Both of these species are widespread

throughout most of the British Isles.

 

3.7 The distributions of C. obsoletus and C. pulicaris group midges in UK are not

efforts have not been made to collect rather than the species is absent there. Generally,

the insects congregate where there are breeding sites and hosts upon which to feed.

Thus, the highest concentrations of C. obsoletus and/or C. pulicaris group midges are

Thus, the highest concentrations of C. obsoletus and/or C. pulicaris group midges are