Return of the Bluetongue Virus in Sheep: Concerns and Precautions

The agriculture department and experts are concerned about the return of the blue language. The virus reappeared in the Netherlands last year after about fifteen years of absence and resulted in the death of tens of thousands of sheep, cattle and goats.

There have been no new infections in recent months, as the insects that spread the virus are not as active in the winter. “But we expect the virus to break out again at any time,” says Saskia Duives-Cahuzak, chairman of the Sheep Farming department at the agricultural organization LTO. “I have said before: ‘Yes I’m holding my breath,’ and I’ll say it again.”

The virus is transmitted by midges, a type of small mosquito. Reproductive animals such as cows, sheep and goats get sick from it. For example, they suffer from fever, stiff legs, swollen tongue and inflammation of the worms. There is still no treatment for the latest version of the blue language.

Last year, bluetongue of the so-called serotype 3 was found at almost 6,000 places in the Netherlands. In December, research showed that nearly 40,000 sheep had died from the virus.

On infected farms where the research was done, about 8 percent of the sheep became sick. Of these, three quarters did not survive. The virus also affected cattle and goats, but was less fatal in these animals.

The midges are less active in cold weather. That is why no infections have been detected this year, but that is a matter of time. “Experience shows that the virus circulates more heavily in the second year than in the first year,” says Duives-Cahuzak from LTO, referring to the outbreak in 2006 and 2007.

“We are very concerned,” says veterinary epidemiologist Inge Santman-Berends in the radio program News and Co. “In 2006 we hoped that the virus would not survive the winter, but then we had fewer infections before the winter and it was a colder and longer winter than the year.”

Experts from the Animal Diseases Experts Group, which advises the Ministry of Agriculture, expect a sharp increase in the number of infections in July or August. But because of the mild winter, the increase could start earlier, they write in a consulting report (.pdf). “From the beginning of summer, maybe as early as June.”

The veterinary epidemiologist Santman-Berends today started a study at the Royal GD Animal Health Service on how many animals have antibodies against the virus. This is done on behalf of the ministry, which wants to see how many cows and sheep could be protected from a new outbreak.

Animal keepers are also asked what measures they take to keep the disease at bay. “If certain measures were taken in that operation, we want to learn from them so that we can help other farmers,” says Santman-Berends. There is a lot of evidence that it helps to keep the animals inside. and ensuring good ventilation. “We don’t have any evidence for this yet and we want to know what kind of installation is involved and what the ventilation is like.”

The Minister of Agriculture who is leaving Adema hopes that an effective and safe vaccine will be approved at the beginning of June, he wrote to the House of Representatives in February. Duives-Cahuzak from LTO also has that hope, but the question is whether that will be successful. “One stroke and it’s August,” she says.

Furthermore, the problem will not be solved immediately once a vaccine is approved. “We hope to have a million doses immediately, but then there are not enough vets to administer the drug. The same thing is happening there as in other regions: lack of people.”

LTO advocates giving priority to the Netherlands over other European countries when they provide the vaccine, since it is the Netherlands that is most affected by the bluetongue. Duives-Cahuzak: “More and more sheep farmers are stopping and there are two reasons: the wolf and the bluetongue. In particular people affected by the bluetongue for the second time say: no need more.”