NEWS IN DETAIL...
A summary of current understanding of this emerging disease produced with information from Defra and the NFU.
By Faye Shepherd & Morwenna Tregellas
What is it?
Schmallenberg virus (SBV) is a newly emerging livestock disease that has been detected in Belgium, France, Germany, The Netherlands, Italy & Luxembourg as well as in England.
The virus has been associated with brief mild to moderate disease (milk drop, fever, diarrhoea) in adult cattle and late abortion or birth defects in new born cattle, sheep and goats. These signs may spread through the herd affecting between 20-70% of animals over a 3-4 week period, and may lead to a drop in herd milk production of about 10%. There have been no reported clinical signs in adult sheep (or goats) from any of the affected countries although there have been anecdotal reports of milk drop in milking sheep flocks.
Congenital defects have been seen in close to term and new born lambs, calves and goat kids. They include joint and limb contractures and twisting (arthrogryposis), twisted neck (torticollis), and animals are usually stillborn, or die soon after birth. Other signs that may not be obvious externally such as hydranencephaly (parts of the brain may be replaced by fluid- filled sacs), could lead to signs of incoordination, paralysis and other nervous signs, including recumbency and dullness.
How is it spread?
It is thought to be spread by infected biting insects such as midges, mosquitoes and ticks. The possibility of direct transmission between animals cannot be ruled out at this stage. Infected females appear to pass the virus on to their offspring if they are pregnant at the time of infection.
Where has it spread?
So far, SBV infection has been identified on 223 farms in the UK. 20 of the positive cases have been diagnosed in cattle, 203 in sheep, and none to date in other species such as goats, camelids or deer (correct as of 26th March 2012).
What should I do if I suspect Schmallenberg virus on my farm?
Whilst this is not a notifiable disease, the NFU is encouraging farmers to contact their veterinary surgeon if they encounter cases of ruminant neonates or foetuses which are stillborn, show malformations or are showing nervous disease, or if Schmallenberg virus is suspected. Veterinary surgeons should then contact their AHVLA/SAC laboratory if they suspect infection with the virus. Details of premises with suspected or confirmed disease are treated as confidential and will not be made publicly known.
How will it be controlled?
Due to the transmission similarities between Bluetongue virus and Schmallenberg, the potential control methods are also thought to be similar-through the creation of a vaccine that offers protection. There are no plans to cull infected animals, as the virus is spread by insects and thus, would be ineffective at stopping disease spread. Pour ons are thought to be ineffective, as the infected fly or midge only dies once it has bitten the animal, and by that time it’s too late.
It is thought that post infection animals develop immunity and are unlikely to be infectious.
Is there a risk to human health?
Fortunately, it appears that the risk to human health is low. A Europe-wide risk assessment has concluded that Schmallenberg virus is unlikely to cause illness in people. This is because the virus belongs to a group of viruses that have not previously caused disease in humans.
However, as this is a new virus, work is ongoing to identify whether it could cause and health problems. For further information please see: www.defra.gov.uk www.nfuonline.com