26 March 1999

IBR MAY POSE QUESTIONS FOR FREE TRADE

IBR could prove to be an increasingly important cattle

disease, particularly politically. Vet Mike Vaughan reports

his findings from a recent IBR conference in Holland

INFECTIOUS bovine rhinotracheitis is a disease with political ramifications in potential restrictions on movement of cattle from herds or countries which are not free of it.

Peter Franken, manager of the Dutch IBR eradication scheme, believes this makes controlling the disease relevant to UK producers. As more of Europe becomes IBR free, access to cattle from non-free herds, or indeed countries, will be denied.

Countries can, and often do, impose health regulations which can constitute a barrier to trade. On January 1, 1999 an EU directive, already delayed for 10 years, came into effect. This states that all AI Stations involved in trade between EU countries must be IBR Free. These stations are forbidden to vaccinate.

Following its introduction from North America in the 1970s, IBR, which is caused by bovine herpes virus-1 has spread over all of Europe.

Once infected, cattle become lifetime carriers of the disease, a feature of herpes viruses. Infected bulls shed virus in their semen and it remains viable in frozen semen for at least a year.

Live vaccines provide effective protection and have been used extensively.

There are also countries which have successfully eradicated the disease. This may be by good fortune, through a low national incidence of infection, or because they have small cattle populations and employ less intensive husbandry. These are the Scandinavian countries and Austria, while France and Germany are also pursuing eradication.

In the UK there are blood and milk tests for IBR and cattle health schemes for those considering future exports and improving their herd health status. In other countries, a marker vaccine provides a practical tool to eradicate the disease, but it is not yet available in the UK.

Eradication of any disease, whether on a national or farm basis, requires testing of all eligible stock and removal of any carriers.

Holland has the highest national herd infection rate, with 85% of dairy herds and half of its beef herds affected. Dutch dairy farmers are keen exporters – exporting 1.3m doses of high genetic merit semen and 50,000 pregnant heifers each year – so a way to eradicate IBR had to be found.

Following research on different strains of viruses at the Dutch Institute for Animal Science and Health, one was discovered which protects against natural infection. It is also safe, and milk or blood tests can differentiate between animals marker vaccinated and those naturally infected or vaccinated using the original vaccines. When used in infected herds, it reduces the amount of virus shed from carrier cattle.

This marker strain has been used by Bayer to develop a vaccine which protects uninfected cattle and also weeds out infected cattle.

Herds with a high incidence of IBR positive cattle will move towards eradication by culling those cattle over time. Herds with small numbers of infected cattle can cull positives earlier to achieve IBR-free status sooner.

A voluntary IBR eradication scheme was introduced in Holland in 1995 and a compulsory scheme started last May. From a level of fewer than 500 certified-free herds in January 1997 there are now more than 12,500 IBR-free herds in a total of 60,000.

The eradication scheme is run by the Dutch Animal Health Service (G-D). Non IBR-free herds must vaccinate all cattle over three months old, using live marker vaccine twice a year. The annual cost is £5 an animal.

Herds which are IBR-free, confirmed by blood testing all animals over 12 months, will be certified free and will no longer have to vaccinate.

Monitoring to see whether herds remain free of IBR will depend on bulk milk tests for dairy herds and blood tests for beef herds. IBR-free herds have strict disease security regulations and can only buy in certified-free animals.

Other dispensations from vaccination are for youngstock under two years blood tested negative and kept separately or veal and beef cattle going straight to slaughter.

Dutch farmers have to pay about 95% of the schemes costs including vaccination, blood and milk tests, culling of infected animals and certification.

The state pays for scheme administration and validation, testing and research. After eradication it will also pay the costs incurred in breakdowns and, where necessary, ring vaccination. Vaccination will cease after eradication is complete. &#42

ERADICATION SCHEME

&#8226 Use marker vaccine.

&#8226 Cull carriers.