Cases of the deadly Schmallenberg virus sweeping across Europe have loomed large in the media in recent weeks. The virus, reported to be “killing thousands of lambs”, has spawned alarming headlines.
These reports are of significant interest to farmers, who are likely to be concerned about their animals’ welfare and potential financial loss, following major incidents of livestock diseases such as foot and mouth, BSE and bluetongue.
Any possible link with human health could be of public concern. However, the fact that Schmallenberg virus is almost certainly confined to livestock has been quite widely reported.
Schmallenberg virus causes transient fever, diarrhoea and reduced milk yield in adult animals. It has also caused stillbirths and foetal abnormalities in lambs, cows and goats. Because the virus has only just been identified, the long-term consequences for infected animals are not yet known.
The virus was first detected in Germany in August 2011 and has since spread through Europe, reaching the UK in late 2011. The full extent of Schmallenberg virus spread is currently unknown. However, according to the Department for Environment, Food and Rural Affairs (Defra), 83 farms (78 sheep farms, five cattle farms) in 14 English counties are now confirmed to have animals that tested positive for the virus (to February 27).
Insects such as midges or mosquitoes are the most likely carriers of the disease, according to the Health Protection Agency. Agriculture and health officials in the UK and other European countries are monitoring the disease to see how it spreads. Defra has said that further spread of the virus to new farms will depend on the seasonal temperature and how many midges migrate as a result.
As yet, no human cases of Schmallenberg virus have been detected in any country, and the most closely related viruses only cause animal disease. Early assessments of the virus suggest that it is unlikely that it can spread to humans.
German researchers have looked at the virus’ DNA and found it lacking genetic sequences that would make it a threat to people. However, human implications cannot be ruled out completely until there is a better understanding of the virus.
Because this risk cannot be ruled out, pregnant women are advised to avoid close contact with animals that are giving birth, as there is a theoretical risk of infection from sheep, goats and cattle that could harm a woman’s own health and that of her unborn child.
Very few pregnant women are likely to come into contact with an infected animal. However, any pregnant woman is advised to seek medical advice if she's concerned that she could have been infected by farm livestock.
The Food Standards Agency has said that on current evidence there is little health risk for consumers from meat. No illness has been reported to date in humans exposed to animals infected with Schmallenberg virus.
The agency advises people to follow normal food hygiene precautions when handling, preparing and cooking all foods, to reduce the risk of food-poisoning.
There is currently no vaccine or treatment for the Schmallenberg virus. However, countries affected by it are monitoring the situation and considering the impact it might have on farms. Researchers are trying to understand how the virus spreads and how it can be treated.
The animal and human health authorities in the UK, other countries and at EU level are collaborating to ensure any changes in the disease are detected quickly. Farmers have been told to report signs of congenital deformities in newborn lambs to their vets. This will help to aggregate information and inform governments and the EU of any ongoing impact.
Some researchers are exploring how the Schmallenberg virus is transmitted and are developing a test to improve detection. If such a test is successfully developed, far larger numbers of infected animals could be found in British farms.