Changes

Jump to navigation Jump to search
409 bytes removed ,  14:18, 20 August 2010
Line 25: Line 25:     
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
Middle East, southern Asia, Portugal, Greece, Corsica, Sardinia, Sicily and areas of Italy<sup>1</sup>, 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, Portugal, Greece, Corsica, Sardinia, Sicily and areas of Italy<sup>1</sup>, 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 the insects tend to gather where breeding sites and hosts occur in tandem, with the highest midge concentrations in areas containing cattle, horses and pigs. Removal of livestock decreases populations of ''Culicoides'' by a factor of 10 to 20<sup>1</sup>, but some persist by feeding on wild animals and man. Hill sites have fewer midges as climatic conditions are less favourable, and sheep have a less positive influence on distribution.
   −
Thus, the highest concentrations of C. obsoletus and/or C. pulicaris group midges are
+
In Britain, studies are ongoing to determine midge distribution, seasonal incidence and the competency of the various ''Culicoides'' species to act as BTV vectors.
found where cattle, horses, pigs and, to a lesser extent, sheep populations are highest.
  −
If domestic animals are removed from a site, over several months the midge
  −
population reduces significantly, by a factor of ten to twenty times, but will usually
  −
persist at the lower level if other ecological factors are favourable, by feeding on wild
  −
hosts and/or humans.Vector numbers are likely to be low in hill sites where sheep are
  −
at low densities and where the climatic conditions are likely to be more extreme.
  −
3.8 Studies of Culicoides spp. in Britain are being expanded under a DEFRAfunded
  −
project out of the Institute of Animal Health, Pirbright. Monitoring is being
  −
expanded to twenty-five or more sites, one of the aims being to determine the species
  −
list, species distribution, seasonal incidence and vector competency of the various
  −
species.
      
===Vector Competency===
 
===Vector Competency===
6,502

edits

Navigation menu