Schmallenberg

Schmallenberg (SBV) is a viral disease affecting cattle, sheep, goats, other ruminants and camelids, with cases mainly recorded in sheep and cattle. 

Schmallenberg is important in ruminants as a cause of fever, diarrhoea and milk drop in cattle, while foetal deformities, stillbirth and abortion are observed in both cattle and sheep.  Foetal deformities and associated dystocia (calving or lambing difficulties) can severely compromise the welfare of affected cattle and sheep and may necessitate a Caesarian section or foetotomy.  The foetal deformities most often observed in cases of SBV include twisted and fused limb joints, curved or twisted spines, domed heads and undershot jaws.

SBV was first diagnosed in N Ireland in October 2012 and there was a significant peak in cases in 2017 and 2018.  Schmallenberg cases in
N. Ireland have been largely absent since 2019.  In October 2024, AFBI diagnosed a case of Schmallenberg virus in a two-month-old calf which had presented as a dummy calf since birth.  Brain abnormalities were present in the calf and genetic material of the Schmallenberg virus was detected in brain tissue on postmortem examination by PCR.  AFBI recorded a second case of Schmallenberg in November 2024 in a full-term bovine calf which presented with rigid joints and a twisted neck, and which required veterinary intervention to be calved (dead) from a heifer.  This diagnosis was based on both the gross pathology and on the detection of antibody to SBV in foetal fluid indicating infection of the foetus during pregnancy.

Cases of Schmallenberg have increased in GB since Autumn 2023 and cases have continued to occur steadily in 2024.  Similarly, the number of cases of Schmallenberg in the Republic of Ireland has risen markedly in 2024.

Generally, the impact of Schmallenberg in N Ireland has been low, but at farm level the impact is highly variable and is likely to depend on the calving or lambing programme used.  AFBI advises vets and farmers to be vigilant for SBV related disease in the forthcoming calving and lambing seasons.  With the midge vector season coming to a close now for the winter, acute disease due to Schmallenberg, predominately fever, milk drop and scour, is unlikely to be seen again before late next Spring.  The possibility of foetal deformities however, leading to calving and lambing difficulties, and potentially significant flock losses, remains an economic and welfare concern, especially in those herds and flocks where mating took place during the active midge season in summer and autumn.  AFBI recommends that farmers submit the carcases of deformed and aborted lambs and calves during the upcoming season to its Omagh or Stormont laboratories for postmortem examination.  For investigation, treatment and prevention of outbreaks of milk drop, fever, or diarrhoea in cattle herds farmers should contact their private veterinary practitioner.

Farmers should also remain vigilant for Bluetongue, another biting midge transmitted viral disease of ruminants and camelids.  Currently bluetongue is having a major impact in mainland Europe, and cases in cattle and sheep have been detected in England (and Wales) since August 2024.  Like Schmallenberg, bluetongue can lead to foetal losses and deformities and should be borne in mind in cases of foetal abnormality.  Bluetongue is a notifiable disease meaning DAERA should be notified on suspicion of the disease.  Schmallenberg on the other hand is not a notifiable disease.

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