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Schmallenberg virus

In December 2011 a new animal disease was found in sheep and bovine animals in the Netherlands, caused by the Schmallenberg virus. The disease leads to congenital malformations, and livestock farmers are obliged to notify the authorities if lambs or calves are born with malformations. This will enable the government to assess the spread of the disease.

Public health risk

Based on all the available information, experts conclude that the transmission of the virus to humans cannot be excluded but is highly unlikely. The National Institute for Public Health and the Environment (RIVM) recommends that the usual hygiene measures are followed after coming into direct contact with animals.

Characteristics of the virus

The Schmallenberg virus has been detected in lambs, calves and adult bovine animals. The disease is new and its origins are unknown. Initial research indicates similarities with the Akabane virus, a pathogen known to affect ruminants in Asia and Australia. It is likely that the Schmallenberg virus is transmitted by midges.

Malformed lambs
In sheep the virus is characterised by congenital malformations in lambs such as a crooked neck, hydrocephalus, and stiff joints. Most of these lambs are stillborn, and those that are born alive are not viable. The ewes do not display any symptoms of the disease.
Sick cows and reduced milk yield
Infected bovine animals suffer from diarrhoea and fever, and also yield less milk. In August and September 2011 these symptoms were reported by more than 80 cattle farms in the Netherlands, and it is assumed that the Schmallenberg virus was the cause. The animals have since recovered.
Schmallenberg virus in malformed calves
Since 23 January 2012 the Schmallenberg virus has also been detected in calves. It was expected that calves would also be affected by the virus. The animals were infected at the same time as the sheep and the goats, although the symptoms of the virus only became apparent later due to the longer gestation period of bovine animals compared to sheep and goats.

Notification obligation for animals born with malformations

Farmers are required to report cases of animals born with malformations to the Dutch Food and Consumer Product Safety Authority (Nederlandse Voedsel- en Warenautoriteit, NVWA). The notification obligation also applies to veterinarians and persons working in research institutes.

The purpose of the notification obligation is for the Ministry of Economic Affairs, Agriculture and Innovation to gain a better understanding of the geographical spread of the problems caused by the Schmallenberg virus. This data is also important for the follow-up research into the disease.

Spread of the disease: Schmallenberg virus map

A map is available on the website of the Dutch Food and Consumer Product Safety Authority showing the locations of the farms where the Schmallenberg virus has been detected, with a chart indicating the number of farms where the virus has been detected per province, the number of farms where the virus has not been confirmed and the number of farms where tests are still being carried out.

Testing method

After a notification is received tests for the Schmallenberg virus are carried out on the congenitally malformed animal. It is possible that this test will not indicate the presence of the virus, as the actual infection occurs at an earlier stage of the pregnancy. A virus antibody test, which would indicate whether the animals have previously been infected by the virus, is under development. It is likely that the number of farms affected by the virus will rise further when the virus antibody test results become available.

Follow-up research

Due to the potentially major consequences for the industry, the government has earmarked budget for further research into the virus. The objectives of the research are as follows:

availability of tests to identify the virus that can be quickly conducted;
better insight into the spread of the virus;
isolation of the virus;
development of a vaccine.

Researchers from various institutes including the Animal Health Service (GD), the Central Veterinary Institute (CVI) and the National Institute for Public Health and the Environment (RIVM) have started carrying out this research in close consultation with their German colleagues.