The Blue Tongue virus is spreading like wildfire among animals in the Netherlands for the first time in 14 years, killing sheep and infecting cattle, reports DairyGlobal.

Hopes for a vaccine

Hopes for a vaccine are high, but producers need to act quickly as new cases continue to emerge. A hidden question in the unveiling of the vaccine is whether the government will implement a mandatory or voluntary vaccination strategy.

The Blue Tongue virus, which is endemic in tropical and subtropical regions, is transmitted by biting insects called midges. It does not infect humans, but the new outbreak is concerning as Dutch animals have been hit by a powerful strain for which there is currently no vaccine available in Europe.

The Dutch Food and Consumer Product Safety Authority (NVWA) has received reports of the virus at over 1,100 combined sheep and cattle farms in the country, with 965 cases confirmed, as reported by NOS. This rate of spread appears to be faster than that reported during the 2006-2008 outbreak.

NVWA received the first reports of the virus in early September from 4 sheep farms in the provinces of North Holland and Utrecht. In 2 weeks from the first detection in the country, the virus was confirmed in 18 sheep flocks and 55 cattle herds.

Veterinarians sent blood samples to Wageningen Bioveterinary Research, where Melle Holwerda (the head of vector-borne and zoonotic viral diseases) and colleagues confirmed the presence of the Bluetongue virus.

They identified the virus type as BTV-3. BTV-3 symptoms appear more severe than BTV-8, which caused the previous epidemic in Northern Europe. The NVWA map shows that Bluetongue has now spread to 8 provinces. Agriculture, Nature, and Food Quality Minister Piet Adema already expects the country's sheep population to be significantly smaller by next year.

Economic impact

Reports show that the disease affects all ruminants and camelids (cattle, sheep, goats, deer, llamas, and alpacas) and has the most significant impact on dairy cattle due to decreased milk production. Direct costs include production losses, animal deaths, and veterinary treatment.

Indirect costs include surveillance, additional measures for animal exports, disease control (preventative vaccination and insecticide treatment), vector monitoring, and management. There is no treatment, and severely affected animals must be euthanized.

The previous outbreak in 2007 involved a milder strain of the virus, which spread to tens of thousands of European farms and cost about 175 million euros in the Netherlands alone, largely due to reduced trade.

Control measures

The Dutch Ministry of Agriculture has advised farmers to keep their animals indoors with sufficient ventilation to keep midges out. Farmers are advised to bring animals indoors before sunset as midges become active during that period.

Of course, there are no medications for sick animals; however, some reports highlight that veterinarians can prescribe anti-inflammatory drugs, but, while this treatment is supportive, it often is not very effective. It's also important to ensure that fresh water and feed are readily available to less mobile animals.

Live vaccine in South Africa

In South Africa, where BTV-3 is endemic, veterinarians use a vaccine containing a live, weakened form of the virus. Although the safety of a South African vaccine is currently being investigated, its adoption is unlikely because this vaccine is not allowed in the European Union due to concerns that the vaccine virus will recombine with circulating strains, increasing their virulence.

NOS reports that the vaccine against Bluetongue, which was provisionally authorized in South Africa, is not authorized in the Netherlands, according to the acting Minister Adema to the House of Representatives. The Veterinary Medicines Agency advised the minister not to allow it due to safety risks and doubts about the vaccine's efficacy, in which initial hopes were placed.

Vaccine development

On the other hand, Melle Holwerda has advised that research should quickly start on a vaccine based on inactivated virus. Adema told the Dutch parliament that pharmaceutical companies are working on a vaccine, but it's not yet clear when it will be available.

During the last epidemic, a vaccine for BTV-8 was developed in about a year and helped the Netherlands and other countries get rid of the virus. "We hope that in May we will be able to vaccinate the first animals," said Holwerda.

Elsewhere, reports show that EU member states and the UK have imposed animal trade restrictions to limit the disease's spread. UK officials, which have been Bluetongue-free since 2010, are concerned that infected midges will blow across the North Sea from the Netherlands. They are monitoring winds and modeling potential midge "plumes." Meanwhile, Bluetongue has also appeared in Belgium.

Farmers are also advised to be on the lookout for clinical symptoms. Clinical signs in cattle include ocular discharges, conjunctivitis, oral mucosal congestion, the development of ulcers, and necrotic lesions on the lips and tongue, as well as edema.

Voluntary or mandatory vaccination?

Analysis of beliefs shows that for a communication intervention, the communication channels used must be credible and trusted by farmers. In their study published in the journal Food Policy, researchers from Wageningen University and Research analyzed the policy tools used by the Dutch government in their Bluetongue vaccination strategy in 2008.

They found that most European member states opted for a mandatory vaccination scheme, while the Netherlands, among others, opted for a voluntary approach. To encourage voluntary participation by farmers, two types of policy tools were implemented.

A communicative intervention was implemented in which the Ministry, as well as farmers' organizations, provided written or oral recommendations to intrinsically motivate farmers to vaccinate their cattle. Subsidizing vaccination costs as an extrinsic motivator was another policy tool implemented.

Along with standard prevention and control measures, the voluntary approach in the Netherlands was sufficiently effective in controlling the spread of Bluetongue from an epidemiological perspective.

With the virulence of the current virus type, it remains to be seen whether the Dutch government will implement a mandatory or voluntary vaccination strategy.