ENGLISH VERSION receiving the virus is generally immunocompromised, they are at much greater risk of developing the potentially fatal neurological form of West Nile …
SHAMONDA, THE NEWCOMER All mosquito-borne diseases thrive as the climate warms: there are more of these insects, and they are active for longer and longer, since the cold weather that halts their activity arrives later and later – below 15 degrees, they stop biting.“ Climate disruption is also upsetting the habits of migratory birds,” stresses Jean-Marc Betsch. The length of migrations, their routes, their destinations and the time spent at wintering sites are all changing. Storks, for example, used to fly to Africa, but a number of them now spend the winter in Spain. The virus’ s“ points of impact” follow this new map of migration. The proliferation of small biting midges known as culicoides is a boon for European Shamonda Virus( ESV), which appeared in Europe this summer and for now mainly affects cows and other ruminants, causing diarrhoea, fever and lethargy. Cows’ milk production can fall by 75 %, and Shamonda also causes abortions. The virus’ s“ big brother” was first isolated in Africa, in Nigeria, in the 1960s. Sick cattle had already been identified in 46 French départements by September, less than three months after the first European cases were discovered.
Shamonda virus has been detected in Switzerland in the brain tissue of two horses with neurological disorders, and also in an equine in the Hérault. At this stage, a cause-and-effect link between the virus and these neurological problems has not yet been formally established, but Shamonda appears to manifest itself differently in horses and in cattle. In a dramatic twist, the first human case of the disease was announced in Lyon in mid-October. The patient, an immunocompromised man in his sixties being treated for leukaemia, has died. So no species barrier seems insurmountable!“ We know that in the years to come, more and more diseases will strike Europe, boosted by global warming and the constant movement of horses,” says Dr Jean-Marc Betsch.“ When an outbreak of equine rhinopneumonitis broke out in Valencia in 2021, some ten hours later the disease had already reached Belgium, carried by a horse lorry. Hence the importance of the RESPE, which monitors the health of the industry, tracks more than sixty diseases and plays a key role in effectively preventing epidemics.”
THE SYMPTOMS OF WEST NILE
70 to 80 % of horses infected with West Nile fever show no symptoms. For the others, i. e. 20 to 30 % of cases, the first signs of the disease are fever and loss of condition. In 1 to 10 % of cases, the virus manages to reach the brain from the bloodstream. The horse then develops nervous disorders, which are usually mild: depression or, conversely, hyperexcitability, and muscle tremors. In the most serious cases of this neurological form, ataxia appears( impaired coordination of movement). These locomotor difficulties can go as far as paralysis. This leads to coma and death in 30 to 50 % of cases, depending on the viral strain. If the horse survives, it takes nearly a month to recover, and after-effects can persist for up to 6 months after infection. On average, one horse in 100 infected with the virus dies of it.
AFRICAN HORSE SICKNESS, A TICK- ING TIME BOMB
Jean-Marc Betsch is categorical:“ The question isn’ t whether African horse sickness will reach France, but when it will arrive.” The arrival of this epizootic would be a health and economic disaster for the horse industry as a whole. The virus, which belongs to the rotavirus family, is transmitted by culicoides midges, like Shamonda. Equines can develop different forms of the dis-
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