Schmallenberg: Farmers urged to be on guard as cases rise

Vets are urging farmers to be vigilant for Schmallenberg virus (SBV) – which can mimic other diseases including bluetongue – as a rising number of early lambing flocks are hit with deadly SBV this season.

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Independent sheep consultant Fiona Lovatt said the UK has seen an increase in SBV.

“I’ve seen SBV in flocks that have been lambing since the beginning of January – a flock down in Dorset as well as a couple in the Cheshire area (22% of lambs born were affected in one of these flocks).

“This is devastating for the farmers and really disheartening for everyone involved at lambing time,” she commented.

APHA has been offering free testing and since December 2023 has confirmed more than 25 cases in England through its scanning surveillance system. However more suspect cases and samples are received daily.

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The majority of the confirmed cases are congenital deformed lambs as a result of intra-uterine infection during pregnancy.

Clinical signs of SBV

Acute clinical disease in adult cattle presents as:

  • Fever
  • Reduced milk yield
  • Inappetence
  • Loss of body condition
  • Diarrhoea.   

Adult sheep and goats generally do not show signs of clinical disease. However, in newborn animals and foetal sheep, goats and cattle, SBV is associated with abortions, animals born dead at term, or with deformities following infection of the dam.

The most susceptible stages of pregnancy for foetal deformities are days 62–180 in cattle and 25–50 in sheep, according to Nadis.  

Important to exclude other viruses

A recent technical webinar saw Rudolph Reichel, small ruminant expert group lead at APHA, stress the importance of ruling out other conditions which could mimic SBV – including bluetongue virus.

This is particularly important due to the new BTV-3 strain circulating in the UK, as less is known about how this serotype presents.

Mr Reichel said recent cases of SBV have been confirmed in November, December and January, showing signs of milk drop in dairy cattle, and fertility issues in sheep. Now, congenital deformed lambs are being submitted, which are likely to have been born end of December/early January, with dams infected four months prior.

Cases have been confirmed via PCR, first in Devon and Dorset, and more recently in Oxfordshire and Gloucestershire.

SBV is spread through culicoides midges, not animal to animal, so usually cases peak in late summer/early autumn. However it’s thought that warmer weather this winter could be responsible for the unusual cases.

Concerned farmers urged to contact vet

NSA chief executive Phil Stocker said: “It is extremely concerning to hear of proven (and assumed) cases of this virus in many areas of the UK. These cases are from animals that were bitten by infected midges back in the autumn during their early stages of pregnancy. 

“NSA would urge all working with sheep and cattle at these times to be vigilant to the signs of SBV and to contact their vets should they suspect the presence of any cases on their farms.”

Dr Ami Sawran of Westpoint Farm Vets commented: “The SBV cases currently being detected are likely due to infection in late summer/early autumn. Most cases confirmed by APHA are in stillborn lambs, but it is worth noting that this may be seen in cattle, goats and camelids.

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“There are currently no plans to offer a vaccine for SBV, however many different diseases can cause abortion or deformation in neonates, some of which are manageable at herd or flock level, so it is important to pursue diagnostics to determine the cause on your farm.

“If you have unfortunately been affected by poor scanning percentages, abortions or issues at lambing and calving, it is important to speak with your vet to determine any management changes that may serve to protect your herd or flock.”

Farmers affected by SBV are encouraged to take part in a survey by the University of Nottingham to help build a picture of the extent of the problem, which can be found here

For more information on free APHA SBV testing visit here

Read more livestock articles here

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