Bluetongue virus
 
Version 02-01-2012.

The disease called "blue tongue" is a non
- contagious infectious viral disease that almost exclusively affects sheep in particular breeds of fine wool and lamb, also the white - tailed deer (Odocoileus virginianus), the pronghorn (pronghorn) and desert bighorn sheep (Ovis canadensis). The latter may develop severe clinical disease in North America. The infection is common worldwide but is usually asymptomatic or mild in most infected ruminants.

The bluetongue virus belongs to the species of the genus Orbivirus of the Reoviridae family. There are 24 serotypes worldwide. It is transmitted by arthropod vectors being nocturnal Diptera ( "Beatillas") Culicoides, Family Ceratopogonidae. In Spain, as throughout Southern Europe, Africa and
the Middle East, Culicoides obsoletus and Culicoides imicola, a thermophilic species of Afro - Asian origin, common throughout the peninsular southwest, are the most implicadops. In Australia, they are Gyps C., C. and C. wadai actoni; and America, C. and C. insignis variipennis. C. imicola breeding manure so the middens and not moved are excellent breeding grounds, while droppings in the countryside tend to dry out too quickly to sustain it . These arthropods are seasonal, operating in summer and autumn, very dependent on moisture, so the disease spread along watercourses, and nocturnal habits. Your flight is limited but can easily be transported long distances by the wind (130-200 km). In the subtropical biotopes, or in some temperate areas, adults can survive throughout the winter.

These arthropods do not transmit the virus to their offspring and become infected by biting a viremic animal. Once
it has infected, the virus multiplies extensively in cells intestine and salivary glands, permanciendo infected the rest of his life. High transmission through percutaneous inoculation. Outbreaks of the disease are related solely to the presence of infective active adults. These Culicoides are present throughout the year in enzootic areas, overlapping different generations and ensuring the permanence of the infection, while in areas where epizootic outbreaks recorded this presence is limited to the warmer months. Ticks can also act as mechanical or biological vector of the disease, but their epidemiological significance is very low.

Clinical manifestations of the disease are variable and depend ultimately on the virulence of the strain involved and affected species. In some animal farms any symptoms does not occur or is very slight, while in others the process can affect most animals. The incubation period is usually between 6 and 10 days, being usually the course of acute or subacute disease. In sheep the process begins with oscillating fever up
to 41 ° C for 2 to 12 days, accompanied by leukopenia, ruminal atony and depression, muscle aches (torticollis), and skin edema, especially cephalic. They can also be produced abortions and fetal malformations in pregnant animals. As sequelae may be torticollis and permanent lameness and hoof pigmented bands. In cows usually subclinical table presenting only slight alterations in leukocyte and lymphocyte blood formula. In the event that there existed prior sensitization with Orbivirus similar to sheep but more mild symptoms may occur.

In many parts of the world, bluetongue in sheep and other ruminants especially, is subclinical and therefore laboratory confirmation based on the identification of viral RNA by PCR is required. In IVAMI we perform laboratory diagnosis
by detecting the RNA genome of the virus followed by a transcription amplification (RT-PCR).

Recommended sample: EDTA whole blood (2 to 5 mL).