The bluetongue Virus

The bluetongue virus is a non-contagious viral arthropod-borne infectious disease due to an Orbivirus (famille Reoviridae, virus ARN), mainly transmitted by hematophageous midges from Culicoides genus. The disease is found in countries where these midges are prevalent and clinical cases have been reported in Africa, the Middle East, the USA, Asia, and southern Europe. It induces serious syndromes by ovine (fever, oedema, slimming, mortality 1 to 10%), but it mainly is asymptomatic by caprine or domestic or wild ruminants, which are the virus reserve.

The clinical expression is widely dependent on the environmental parameters (nutritional state, parasitism and bacterial infections concomitant) and on the individual sensitivity. 24 distinct serotypes exist inducing partial or no cross protections between them.

Under the natural conditions, the dissemination is exclusively the fact of infected biting midge or the seed of infected males. The diffusion of the disease thus is largely influenced by the activity of the midge. Transmission by pregnant ewes has also been described. Transmission by contaminated blood injection is possible when needles and syringes are re-used. Samples for virus detection are bloods of animals with anticoagulants. Virus is detected by isolation on embryonated eggs, in vitro cell culture, immunofluorescence on cell culture or by PCR.