WUR: alertness for EHDV needed

Epizootic Haemorrhagic Disease Virus (EHDV) is genetically related to bluetongue virus; both viruses are Orbiviruses. Deer are particularly susceptible to EHDV infection, but cattle are as well. Infected cows show symptoms very similar to those of a bluetongue infection. Like bluetongue, EHDV is transmitted by midges that pick up the virus via a blood meal from an infected host.

Spread

Previously, EHDV occurred mainly in the Americas, Australia and Africa. In 2022, the virus made the leap from North Africa to Europe. That year, EHDV serotype 8 was first observed in Europe with clinical cases in Italy, Portugal and Spain. In 2023 the virus moved further north as far as France. This year the disease progresses further to the north, heading to the Belgian border.

Spread of a viral disease in animals over a wider area and in a more northerly direction, is not new. The outbreaks of bluetongue serotype 8 in 2006-2008 and the current bluetongue outbreak with serotype 3 underline this. “However, the spread of EHDV in Europe does prompt us to be extra vigilant, including by collecting and analysing midges for the presence of viruses together with NVWA Centre for Vector Surveillance,” says Melle Holwerda, project leader of two research projects currently underway aimed at detecting viruses transmitted by midges. Both projects are funded by the Ministry of Agriculture, Fisheries, Food Security and Nature (LVVN).

Symptoms

EHD virus causes oedema, bleeding and ulcers (sores) in cattle due to the deterioration of small blood vessels. As a result, inflammations in the mouth, nose and legs may occur, as well as lameness. “The clinical picture is very similar to that of bluetongue. Especially now that we are in the middle of a bluetongue outbreak, the presence of EHDV can easily be overlooked,” Holwerda says. He urges farmers and veterinarians to look at the clinical picture of sick animals with an open mind. “EHDV has spread very rapidly in France,” notes the WBVR project leader. The scientific committee of the Federal Agency for the Safety of the Food Chain in Belgium calculated in July 2024 that the virus is spreading at an average rate of about 20 kilometres per week, according to a report in the Dutch trade journal Veeteelt (Tropical EHD virus can reach Belgium within 30 weeks). In France, it was decided to impose a transport ban with a zone of 150 km around the identified outbreak, meaning that animals from this zone cannot be transported to another member state.

EHDV is a notifiable disease, category D+E according to the Animal Health Law 2021. A suspicion of it must be reported to the Netherlands Food and Consumer Product Safety Authority (NVWA). European legislation requires the disease to be monitored and, if necessary, measures taken to prevent further spread in the European Union. EHDV is not zoonotic and is not transmissible to humans.