The Department of Agriculture has confirmed that one Irish flock of sheep is under restriction for maedi visna (MV).

MV, also known as ovine progressive pneumonia (OPP), is a persistent infection of sheep and goats.

The first confirmed cases of MV were detected in Ireland in 2020 in two flocks, which had a common source of sheep. It was then identified in a third farm in 2022.

All three farms have since been voluntarily destocked.

Responding to a query from the Irish Farmers Journal, the Department said that MV has been identified on farms in a small number of counties, with one farm currently under restriction due to the disease as of 23 December 2024.

Highly infectious

The highly infectious viral disease is mainly transmitted to lambs by ingesting milk from infected mothers, although it can also be spread by direct contact between sheep.

The main clinical signs are respiratory issues, which cause shortness of breath, and also mastitis, with udders that are hard and lumpy, although generally non-painful. Sheep can also develop neurological problems, where they are eventually unable to stand.

There are concerns in Northern Ireland that the prevalence of the virus might increase after its Department of Agriculture, Environment and Rural Affairs (DAERA) announced its plans to end a surveillance programme for MV.

Currently, Northern Ireland has retained its MV-free status due to extensive testing, tracing and removal of infected animals. However, there are fears this plan could lead to the disease entering the country.

No vaccine

According to the Department, there is no vaccine for MV and the only safeguard is the purchase of sheep from flocks/countries with a solid proof of freedom.

Occasionally, animals which test positive following a blood test are identified through post-import sampling or through blood test-surveillance of cull ewes in Ireland. Such cases are followed up on an individual basis.

Along with caprine arthritis-encephalitis (CAE), MV is often grouped together as the small ruminant lentiviruses (SRLVs).