This respiratory disease is caused by a virus infection. The virus mainly affects the upper respiratory tract – particularly the windpipe. Occasionally it can cause abortions or infertility. Affected animals often have very high temperatures and can be very sick. Secondary pneumonia can also occur and the infection can be fatal. However in some cases an animal may become infected without having shown obvious signs of disease.
IBR has been eradicated from a number of European countries due to its economic importance and others have control programmes in place. It can therefore act as a barrier to trade if herds are infected.
The infection is caused by a herpes virus which is the same family of viruses as the cause of cold sores in humans (IBR is not infectious to humans). Following an infection with IBR virus the virus remains in a silent form within the animal but the virus can start being shed again if triggered, for example by stress. Stressors could include calving, transport, change of group, bullying, showing and weaning. However some animals can go through life and never shed virus again. It is impossible to predict which ones may or may not shed again so all infected animals need to be considered a potential risk to uninfected cattle. The virus can be found in the semen of infected bulls so IBR antibody positive bulls cannot be used at AI centres for semen collection.
Vaccines are available which can aid in the control. Some of these are marker vaccines, which means that a specific blood test can be used to differentiate the antibodies generated by the vaccine from the antibodies produced as a result of a natural infection.
Herds can be tested through the IBR programmes to gain Accredited or Vaccinated Monitored Free status.