Schmallenberg Virus

Schmallenberg Virus (SBV), part of the Simbu serogroup of orthobunyaviruses, is an emerging threat to ruminant species across the UK—especially in sheep and dairy cattle during key stages of the gestation period. The virus, transmitted via biting midges, causes intrauterine infection, leading to fetal malformation, congenital deformities, and foetal abnormalities.

With no vaccine currently available, increasing case numbers, and limited visible symptoms in live animals, farmers need to be proactive in managing the risk—particularly during early lambing and calving seasons.

What is Schmallenberg Disease?

Schmallenberg disease affects cattle, sheep, and goats, and is caused by the Schmallenberg Virus (SBV), which spreads through midge populations, particularly during warm, late summer and early autumn months. Once an infected midge bites a susceptible pregnant animal, the virus crosses the placenta and targets the developing foetus.

This results in an increase in:

Stillbirths and abortions
Brain and spinal cord abnormalities
Joint contractures and twisted limbs
Rising lamb mortality across sheep populations
Economic losses for both beef and dairy cattle farms

Where is Schmallenberg Virus Spreading?

Confirmed cases have been reported across:

Wales (e.g., Pembrokeshire, Carmarthenshire, Ceredigion)
South and South-West England (e.g., Cornwall, Devon, Dorset, Somerset)
Central and Eastern counties (e.g., Herefordshire, Gloucestershire, Warwickshire, Oxfordshire, Kent)

According to the Animal and Plant Health Agency (APHA), between December 2023 and January 2024 alone, 63 confirmed SBV cases were reported—many linked to congenital deformities in lambs.

Symptoms of Schmallenberg in Livestock

In most adult animals, SBV presents with mild symptoms or none at all. In adult cattle, look for:

Fever
Reduced milk production in dairy cattle
Diarrhoea

However, in sheep and goats, the virus often goes undetected until birth, where affected lambs may present:

Bent limbs, twisted necks
Fluid accumulation (hydrocephalus)
Stiff joints and underdeveloped muscles
Neurological damage to the brain and spinal cord

These visible symptoms are usually a result of intrauterine infection during early to mid gestation period.

Is Schmallenberg Contagious?

SBV does not spread directly between animals—it requires midges to transmit the disease. However, infected animals can trigger localised outbreaks if midge numbers are high and biosecurity practices are poor.

There is no public health risk, and meat and milk from infected animals remain safe for consumption.

Immunity and Risk of Reinfection

Animals that survive infection typically develop herd immunity, which reduces their risk of future illness. However, new youngstock born after the last major outbreak (2016–2017) may not have prior exposure, leaving large segments of the ruminant species population unprotected.

Understanding whether a flock or herd has been exposed previously can be determined through serology testing—essential for managing future breeding strategies.

Prevention and Control of Schmallenberg

While there’s currently no Schmallenberg vaccine available in the UK, the following prevention strategies can greatly reduce the risk:

Adjust Mating Dates

Avoid breeding during peak midge activity, typically late summer into autumn. Later mating reduces the chance of infection during the most vulnerable periods of foetal development.

Control Midge Populations

Use insecticides responsibly to reduce midge contact (ensure compliance with withdrawal periods). Keep housing dry and clean to reduce breeding grounds. Time animal turnout to avoid dawn and dusk when midge numbers spike.

Conduct Serology Testing

Use blood tests to check for SBV exposure and current herd immunity levels. This is especially important before planning breeding or investing in stock.

Take Advantage of Free Testing

The APHA offers free Schmallenberg testing for malformed lambs and calves. Work with your local Veterinary Investigation Centre for submissions.

Implement Biosecurity Practices

Quarantine new or returning animals. Maintain strict hygiene protocols and disinfection procedures. Minimise on-farm movement of animals during high-risk periods

Impact on Livestock and Farm Productivity

The economic and welfare impacts of Schmallenberg can be severe:

Increased lamb mortality and stillbirths
Reduced fertility rates and productivity in dairy cattle
Loss of breeding stock due to congenital deformities
Long-term impact on herd performance and genetic progress

Stay Organised During Calving & Lambing with Herdwatch

Tracking births, veterinary visits, and health incidents has never been easier. With the Herdwatch App, you can:

Record calf and lamb births in seconds
Stay compliant with medicine and treatment logs
Track abnormalities or mortalities by tag
Maintain clear digital records for inspections or audits
Save up to 3 hours a week on paperwork

Used by over 22,000 UK and Irish farmers, Herdwatch is the trusted digital solution to stay ahead of disease risk and keep your farm data in one place.

Stay alert for signs of Schmallenberg disease, use serology testing where appropriate, and ensure thorough record-keeping with tools like Herdwatch. Until a vaccine is reintroduced, these steps remain the frontline defence for UK livestock farms.