Schmallenberg Virus 

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Background
 
Between August and October 2011, outbreaks of disease in adult cattle that included mild to moderate fever, reduced milk yield, loss of appetite, loss of body condition and diarrhoea were reported in both the Netherlands and Germany. Testing for common causes proved negative.

From November 2011, abortion and stillbirths associated with foetal abnormalities, affecting mainly sheep but also cattle and goats, were identified in the Netherlands, Germany and Belgium.

A new virus was identified in December 2011 as the cause of both conditions. This was named ‘Schmallenberg virus’ after the German town where the virus was first identified.

In early 2012, the first cases were suspected in the south and east of England. In these initial cases, the disease was diagnosed following the testing of deformed lambs.

Schmallenberg virus is in the Simbu serogroup of the Orthobunyavirus group. This group of viruses includes many different viruses which occur in Asia, Africa and Australia, but have not previously been identified in Europe.

As this is a newly identified virus there are still aspects of the disease that remain unknown at this point until more research has been done.

Geographical distribution

The disease became widely distributed throughout the  UK in late 2012

Species affected

Currently we know the virus will infect and cause disease in sheep, cattle and goats.

Transmission

Orthobunyaviruses are typically primarily spread by biting insect vectors, such as midges and mosquitoes, although the routes of Schmallenberg virus transmission have not yet been confirmed. The potential for direct transmission (i.e. direct from one animal to another) is therefore, as yet, unknown.

If biting insect vectors are the major route of transmission, significant spread is believed unlikely during the winter period when biting insects are usually inactive.

It is believed Schmallenberg virus was circulating widely in sheep and cattle in the Netherlands and in a part of western Germany between August and October 2011. The initial introduction of the virus to the UK therefore may have resulted from either wind-blown insect vectors or via imported infected livestock during this period.

Research work suggests that live infected animals have virus in their bloodstream for two to six days, when biting insects can pick up the virus and transmit to other animals blood-feeding.

The potential for spread directly between animals is not yet known.

Clinical signs

In adult cows, cases of acute infection have resulted in diarrhoea, fever, a reduction in milk yield, with a full and rapid recovery over several days. Affected herds had outbreaks of disease lasting two to three weeks. In other species this stage of the disease has not been noted.

Clinical signs have not been reported in adult or growing sheep.

In newborn animals and foetuses, the disease has been presented as malformations
including bent limbs and fixed joints, brain deformities and marked damage to the spinal cord. Some animals are born with a normal outer appearance but have nervous signs such as a ‘dummy’ presentation or blindness, ataxia, recumbency, an inability to suck and sometimes fits. The foetal deformities vary depending on when infection occurred during pregnancy.

Cases were confirmed in our area commencing in December 2012

Risk to humans

At the moment, a Europe-wide risk assessment has concluded that Schmallenberg virus is unlikely to cause illness in people. As yet, no human cases have been detected in any new country, and the most closely related viruses only cause animal disease.

However, as this is a new virus, work is ongoing to identify whether it could cause any health problems in humans.

Farmers and veterinary surgeons are advised to take sensible hygiene precautions when working with livestock and abortion material. Although several members of the group of related viruses can affect humans, the ability to do is thought to be due to a gene sequence which is not present in Schmallenberg virus.

Pregnant women should not have contact with sheep and goats at lambing/kidding time due to risks of exposure to other disease causing organisms.

Treatment and control

A new  vaccine Bovilis SBV made by MSD has just been launched on  to  the  market.Sheep  require 1 injection and cattle 2 injections separated by an interval of 4 weeks, immunity is effective from 3 weeks after the completion of the  vaccination course.The duraton of  protection provided by the  vaccine is unknown and it  is  not  licensed for  use in pregnant animals

Diagnosis - What  happens  if  you  see  a  suspicious case??

This is not a notifiable disease, but please contact us if they encounter cases of ruminant neonates or foetuses which are stillborn, show malformations or are showing nervous disease.Confirmation of infection is by detection of virus sequences using real time PCR on tissues. There is also  a  blood test available which tells us whether an animal has been exposed to  the  virus

Please  contact  the  surgery  and  ask  to  speak  to one  of  the  Farm vets if  you  have any queries.

 

 
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