With no national plan to eradicate IBR, steps need to be taken on an individual farm basis to stop the disease.
Despite there currently being no plans for national eradication of infectious bovine rhinotracheitis (IBR) in the UK, the decision on whether an IBR elimination programme should be a priority for your herd needs to be taken on an individual farm basis.
Tim Geraghty, of SAC Consulting, explains signs of infection in a herd can vary from severe respiratory disease to sub-clinical infection with no obvious signs. However, the virus can also cause abortion.
“Because of the variation in clinical signs the economic and welfare cost can vary greatly between infected herds too. Eliminating IBR will reduce these costs. There are other advantages of being free from the infection, including the ability to sell disease free stock. For international trade, semen for AI must be harvested from IBR free animals.”
In the UK, there are several health schemes which allow a herd to become ‘accredited free’ from IBR. Cattle Health Certification Standards (CHeCS) approved schemes, such as the Premium Cattle Health Scheme run by SAC, all work to an agreed set of standards. Within these schemes, herds can follow defined control strategies to reach a disease free or vaccinated and monitored free (VMF) status.
“If you decide to try to eliminate IBR a good first step is to check your vaccine history with your vet. Some IBR vaccines can be used during elimination programmes as they can be differentiated from natural infection – these are called ‘marker vaccines’. Use of other vaccines, called ‘non-marker’, prevent disease free status being achieved in the short-term. If you have been using non-marker vaccine, the only step to take in the short-term is to move to a ‘marker’ vaccine.”
Mr Geraghty says the next step is to estimate the level of infection in your herd. “This can be done by joining a CHeCS scheme and carrying out a ‘first qualifying’ test. This means testing all animals over 12 months of age and any purchased cattle for IBR antibodies.
“A cheaper alternative would be to test a smaller number of animals. This would not be suitable for CHeCS programmes, but can give you an idea of level of infection. The type of test to use will depend on previous vaccine use and should be discussed with your vet.”
Where there are no test positive animals on a CHeCS qualifying test, the focus for the herd should be on maintaining biosecurity to prevent infection. Accreditation can be achieved following two clear qualifying tests carried out between one and 12 months apart.
To maintain disease free status an annual herd test is required. In addition, clinical outbreaks of respiratory disease, abortions or stillbirths should be investigated.
If there is a low prevalence of test positive animals (typically 5 per cent or less) a strategy to either cull or isolate the infected stock may be feasible with a focus on reaching accredited or vaccinated and monitored free (VMF) status quickly. Qualifying tests can be repeated at a minimum interval of three months until two clear tests have been achieved.
In herds where more than 5 per cent of animals are test positive, a strategy to reduce the spread of infection using regular vaccination with a marker vaccine combined with a testing protocol to monitor prevalence is more appropriate. When testing shows herd prevalence has fallen below 5 per cent, or when all the original test positive animals have left the herd, a strategy to reach accredited or VMF status can be adopted.