Scientists from the Royal veterinary College and Institute for Animal Health have revealed that the Schmallenberg Virus has overwintered in the UK and could spread beyond its current range as midges become active this season.

The virus, which causes relatively mild symptoms in adult cows, sheep and goats, but can cause spontaneous abortion, stillbirth and congenital deformities in foetuses if animals are infected during early pregnancy, is thought to have spread to the UK in autumn last year, after infected midges were blown over the channel from Mainland Europe, where eight other countries have reported infections.

Experts had previously suggested that the disease may overwinter in the UK’s midge population. SBV is spread by biting insects in the same way as other viruses in its group including Akabane and Bluetongue. Although the disease belongs to the same group, researchers have suggested it may be less severe than the other diseases, as SBV affects below a third of newborn animals and those infected appear to develop immunity to the virus.

It is thought that, if the virus does move into previously unaffected areas, it will cause similar effects to those seen last year, although veterinary scientists have been loath to make detailed projections due to the novel nature of the disease; Schmallenberg virus was first discovered in Germany in autumn 2011.

Although work towards developing a vaccine is said to be progressing well, Animal Health experts said it will not be available in time for use this season.

Carl Padgett, President of the British Veterinary Association, commented on today’s revelation, “We are not surprised that the virus may have over-wintered as this was always a possibility. Today’s news underlines the vital importance of surveillance, monitoring and reporting. It is important to emphasise that at this stage we have only seen evidence of the virus circulating in a small number of animals and so we need to keep the situation under review. We must be watchful for new cases in the currently infected areas."

276 farms in England have reported SBV infection. Of these, 53 are cattle premises, 220 are sheep farms and 3 have reported infections in both cattle and sheep. Although goats and buffalo have been affected in mainland Europe, there have been no reported cases to date in the UK.

Infections last year were localised to the South of England and Areas of the Midlands, where infected midges from mainland Europe are thought to have reached, although cases have been reported in some counties previously deemed to be at a ‘low risk’ of infection, including Lincolnshire and Leicestershire.

Scientists from the Institute for Animal Health have said that “The whole of Great Britain must be considered a risk zone this year,” as infected midges are likely to spread the disease to regions previously unaffected. As the disease spreads quickly, having covered an area from France to England and the Netherlands in just one year, experts have said animals in Scotland, Wales and potentially Northern Ireland are at risk.

AHVLA scientists said last month that surveillance work is ongoing and that animal health experts are continuing to investigate the virus and increase knowledge around it. A spokesperson said, “Using the most up-to-date knowledge to diagnose the disease we are reviewing previous cases where clinical signs and testing of brains did not provide consistent conclusions, as the testing of foetal fluids may be of additional value in diagnosing SBV.”

Both AHVLA and BVA have advised farmers and vets to report unusual symptoms and “to share as much information as possible to continue to progress our understanding” in an effort to improve understanding of SBV.

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