A total of 12 cattle herds and 10 sheep flocks tested positive for Schmallenberg in 2024, data from the Department of Agriculture shows.

Of the 12 cattle herds, 15 animals tested positive for the virus, which is associated with fever, milk drop and diarrhoea, as well as abortion and deformed foetuses.

Last year, 384 cattle from 221 herds were tested for the disease. Some 84 sheep from 61 herds were tested. Of this number, 10 sheep in 10 flocks tested positive.

In the year to 13 January, eight cattle have been tested for the disease with none testing positive. Four sheep have been tested, of which two were positive for Schmallenberg.

Spread

Schmallenberg virus is transmitted by midges (Culicoides species), of which there are 25 species in Ireland.

The Department of Agriculture has said that adult males and females feed on nectar, but females need a blood meal for the eggs to mature.

“Most biting activity occurs from April to December. The larvae can overwinter, but there is no evidence to show that the virus overwinters in the larvae. Larvae can survive for up to a year. It is thought that overwintering occurs through low-level midge activity over the winter.

“The virus has also been found in the spleen of animals for longer periods than in other tissues,” it added.

Schmallenberg virus was first identified in Germany and the Netherlands in the summer of 2011.

Windborne dispersal of midges facilitates the spread of infection over a wide geographical area. It is suspected that the virus was carried by midges by wind borne spread from Europe to the UK. It is not clear whether it was spread to Ireland by the wind or through imported animals.

Irish cases

The first case of Schmallenberg was diagnosed in Ireland in October 2012 and over the following five months, the virus was detected directly in 49 cattle holdings and 30 sheep holdings. However, the Department said that as the condition is not notifiable, it is likely many more cases were never taken to a laboratory for confirmation and therefore have gone undetected.

There was no further evidence of Schmallenberg transmission in Ireland until October 2016, when the virus was detected in a malformed bovine foetus.