The Agri-Food and Biosciences Institute (AFBI) recently confirmed eight Schmallenberg virus (SBV) sheep abortion cases in Counties Fermanagh and Tyrone in Northern Ireland.

Public domain image/Titus Tscharntke
Public domain image/Titus Tscharntke

These are first virus positive cases confirmed by AFBI in the west of the province.

The Department of Agriculture, Food and the Marine in the Republic of Ireland have also recently reported suspected cases in counties Sligo, Cavan and Leitrim. Antibody has also recently been detected in blood samples from ewes in Armagh, Antrim and Fermanagh, indicating exposure to the virus or vaccination.

Schmallenberg virus was first detected in Northern Ireland in a cattle herd in County Down in October 2012. Three further cases were confirmed the following spring in County Down in two cattle herds and one sheep flock. In 2017, the virus reappeared and was detected in one ovine abortion in County Down. Last year AFBI also detected positive tests for antibodies to Schmallenberg in two calves born with skeletal deformities and a cow from a herd experiencing abortions and calf abnormalities, providing evidence that the virus was circulating again in Northern Ireland.

Schmallenberg virus is transmitted to livestock by Culicoides biting midges.  These midges are very effective at transmitting SBV and are very difficult to control, or prevent from spreading the virus.  Although they are less active during the colder winter months, temperatures last winter were not low enough across the British Isles to kill all infected midges.

Problems with malformed calves and lambs arise when pregnant cows and sheep are exposed to the virus during a critical time window in early to mid-pregnancy.  Following infection, exposed animals may give birth to malformed progeny but are likely to develop a strong immunity to subsequent infection.  They are therefore unlikely to suffer any ill-effects if exposed to the same virus in subsequent years.  Commercial vaccines against the Schmallenberg virus are also available for use in cattle and sheep.

Schmallenberg virus (SBV) was first identified in Germany in late 2011 as a cause of malformations in newborn calves and lambs. This virus can cause a temporary dip in production, such as milk output. However, the greatest economic impact comes from abortions, stillbirths and birth defects that can result when pregnant animals are affected.

There is no evidence of any risk to humans from SBV infection.