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Bluetongue at a glance
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Bluetongue (BT) is a non-contagious, viral disease affecting domestic and wild ruminants (primarily sheep and including cattle, goats, buffalo, antelope, deer or elk) that is transmitted by midges of the Culicoides species.
The virus which causes BT is identified as a member of Orbivirus genus of the family Reoviridae. The BT virus species, or serogroup, contains 24 notifiable serotypes, and some other atypical serotypes recently described.Infection with bluetongue virus (BTV) can occur asymptomathically in many animals, but can cause fatal disease in a proportion of infected ruminants. The severity of disease varies among different animal species and viral strains with symptoms being most severe in sheep resulting in deaths, weight loss and disruption in wool growth. In highly susceptible sheep, morbidity can be as high as 100%. Mortality averages from 2-30% but can be as high as 70%. It is not known to affect humans.
The BT virus has been shown to be present in regions where the Culicoides is present (e.g. Africa, the Americas, Australia, the Middle East and some countries of southern Asia). BT situation in the EU has considerably changed in recent times. Since 1998 BTV has been present in Southern European and Mediterranean countries from which it has gradually spread to areas previously free of the virus. In Northern Europe BT virus serotype 8 epidemics broke out suddenly and unexpectedly in August 2006.
Vaccination can prevent clinical BT and mitigate its course by interrupting the BT virus cycle in the environment; it thus reduces the economic losses due to animal infection and makes transfer and trading of animals from BTV enzootic regions possible. Bluetongue vaccines are serotype-specific and therefore, before use in a given area, the serotypes present in the environment should be taken into account. Two types of vaccines, inactivated and live attenuated, are currently available.
