The rate of spread of the current outbreak of bluetongue virus serotype 3 (BTV3) in northern Europe is concerning, especially given the recent case in Britain.

Ireland is currently officially BTV-free.

An outbreak of BTV in Ireland would likely have a very negative impact on animal health and welfare and the livestock sector, with live trade being severely impacted.

Considering this heightened risk, the Department of Agriculture is urging all stakeholders to be vigilant for signs of disease and to think carefully when importing ruminant animals, especially while this current BTV outbreak in northern Europe continues to spread.

Restriction zone

If an outbreak of BTV were confirmed in Ireland, a restriction zone with a minimum radius of 150km from the infected premises would be established with movement restrictions on live animals and germinal products, such as semen and embryos.

Depending on the epidemiological situation of the confirmed outbreak and any subsequent spread the restriction zone may need to be extended to the entire country.

Transmission of BTV occurs primarily when biting midges (culicoides species) feed off the blood of an infected animal and then spread the virus to subsequent animals they bite.

Controlling diseases that are transmitted between ruminant hosts by disease vectors such as midges is extremely challenging in the absence of an effective vaccine.

While vaccines may be available for other BTV serotypes, unfortunately, there is no EU authorised vaccine for the control of BTV3.

Biting midges

In October 2012, Schmallenberg virus (SBV) was identified in Ireland – this too is a virus which is spread by infected biting midges.

The route of introduction of this virus to Ireland was most likely by long-distance displacement of infected culicoides, biting midges, aided by suitable wind flows from continental Europe via Britain.

While importation of an infected imported animal or the offspring of a previously infected animal remains the highest risk pathway, the potential introduction of BTV into Ireland through windborne spread of infected midges is also possible.

Department measures

Measures the Department is taking to mitigate the risk of incursion of BTV:

1 Risk-based surveillance post-import to ensure early detection of disease and help prevent its spread into the Irish midge population. It is vital that our Irish midge population is not spreading the infection.

The most likely route of entry posing the greatest risk of infection of midges is an infected imported animal or the offspring of a previously infected animal.

Experience has shown that even animals certified as being protected from BTV (vaccinated) can harbour BTV. The Department tests all imported animals twice and also ensures that any offspring from animals which were pregnant at the time of import are subsequently tested for BTV.

2 Policy of stamping out if the disease is detected: if BTV is confirmed the infected animal(s) and any at risk cohorts will be destroyed to mitigate the risk of onward transmission via the midge population.

3 Monitoring the spread of the vector (biting midges). The Department uses atmospheric dispersion modelling to identify environmental conditions suitable for atmospheric dispersal of midges from potential infected source locations across southern England and continental Europe.

Wind speed and direction can also affect how far midges can travel and could potentially facilitate the spread of the disease.

This information is used in our disease surveillance programmes for BTV, targeting animals from farms on the east coast of Ireland in order to ensure proof of disease freedom and it can be used to detect disease early as happened in England with the recent BTV outbreak.

4 The Department is working with other EU member states to find an effective vaccine to assist with the eradication of the current BTV3 outbreak in northern Europe. Vaccination can be effective in curtailing infection of midges (vector contamination), especially where an outbreak is spreading.