But the veterinary authorities also detected, on August 30, another serotype of the disease, BTV-3, in a farm in the canton of Jura and another in the canton of Solothurn. This serotype, which had never before been recorded in Switzerland, but which was already present in Germany and France, has a higher mortality rate than the first, especially in sheep.
“The epidemic is of particular concern to breeders, particularly BTV-3, since it is a new variant which has appeared, which is progressing very quickly, and for which none of the three commercial vaccines available is authorized in Switzerland,” notes Tiziana Boebner, spokesperson for the OSAV.
The prevalence of BTV-3 has increased significantly in the country since the detection of the first case six weeks ago: as of October 11, Switzerland had 1,025 farms affected by this new variant. According to the OSAV, BTV-3 currently affects around twenty cantons north of the Alps; the Jura dominates, with 199 farms affected. As for BTV-8, it affects 152 farms in eight cantons, including Vaud, which records the most cases, and Ticino.
A mortality rate reaching 40%
Blue tongue disease is a non-contagious viral pathology affecting ruminants and camelids (camels, dromedaries, llamas, etc.). It is a small mosquito, a ceratopogonid, which is the cause of the contamination. Of subtropical origin, it is moving further and further north, due to trade and climate change, so that all continents are now affected. It is present in Central Europe from April to the end of November.
There are at least 26 different serotypes of the virus, each with its own virulence and spread. Symptoms consist of high fever, which may be accompanied by inflammation of the mucous membranes. Vascular disorders cause bleeding and the formation of edema, particularly in the head and extremities of the animal. A bluish tint (cyanosis) may appear on the muzzle and tongue, hence the name of this pathology. Foamy salivation, runny nose and respiratory problems are also common.
Although animals can recover from the disease, BTV-3 causes deaths in both sheep and cattle. The mortality rate among sheep can be very high, reaching up to 40% on some affected farms in Europe. “In certain cases, if the analgesic treatment does not work and the animals suffer too much, veterinarians can euthanize them,” says Tiziana Boebner. The disease is not dangerous for humans and does not cause contamination of dairy or meat products.
Vaccination campaign in France
Currently, the preventive measures recommended to breeders are the confinement of animals at dawn and dusk, as well as the use of very fine mesh mosquito nets and insecticides, which limit the probability that animals will be bitten. Repellents can also reduce the number of mosquitoes in the barn. It is also recommended to eliminate stagnant water, as it provides an ideal breeding ground for insects, says Tiziana Boebner. “But it is hardly possible to completely protect animals against mosquitoes,” she admits.
In France, a vaccination campaign is underway, although in the European Union, no vaccine against BTV serotype 3 is currently authorized. Unlike Switzerland, the EU has a legal basis which allows member states, in certain circumstances, to authorize the use of an unauthorized vaccine. “The FSVO works intensively with the vaccine approval service Swissmedic and relevant partners so that a vaccine can be imported into Switzerland. Vaccine manufacturers can also request authorization from Swissmedic,” notes Tiziana Boebner.
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