IBR is caused by bovine herpesvirus 1 (BoHV-1). The virus causes an acute upper respiratory tract disease which can lead to fatal pneumonia.
In adult cows, infection is associated with a severe and prolonged drop in milk yield, reduced fertility and abortions. However, on occasions, the disease may be so mild that it may be overlooked. The virus is shed in secretions from the respiratory tract but can also be spread in the semen of infected bulls.
- Nasal discharge (can be clear but is often milky-white)
- Conjunctivitis (red eyes)
- High temperature
- Loss of appetite
- Dramatic drops in milk yield may be first sign
- Difficulty in breathing and coughing may occur but not consistently
- Death can occur in severe cases
- Abortion is seen in some animals with clinical signs
Movement of such animals into a herd is often the source of new infections. Vaccination is an effective means of control, but this does not stop infected animals from shedding the virus at a later date.
IBR is endemic in the UK and in many parts of the world, but some countries are free and there are moves in other EU countries to eradicate the disease.
Despite the effect this disease has on animal health and productivity, its main significance is as a barrier to the export of live cattle to other regions or countries within Europe, where the disease has already been eradicated. In
future, in order to gain access to these markets, herds will have to be able to prove freedom from BoHV-1 infection.
Cattle are the main source of the virus, virtually all farms with an IBR problem have bought it in. The main source of the virus is not animals with disease but animals that have recovered from disease, as these cattle still have the virus in their body (they are ‘latently’ infected) You should not buy antibody positive cattle if you are IBR free.
There are several effective vaccines on the market, discuss with your vet which is the best for you. The main problem with most vaccines is that they produce antibodies which cannot be distinguished from those caused by natural infection. Thus, vaccinated cattle cannot be separated from latently infected cattle. A new vaccine is now available which does not produce the same antibodies as natural infection. This is helpful if you are trying to eliminate rather than control IBR.