Infectious bovine rhinotracheitis (IBR) is a viral disease caused by bovine herpesvirus 1 (BHV-1) that can also cause a mild venereal infection in adult cattle or a brain infection in calves. IBR is a highly contagious disease of the upper respiratory tract and can lead to serious primary or secondary pneumonia. The clinical signs of the disease are nasal discharge, fever and conjunctivitis. Acute disease in dairy cattle is usually accompanied by a severe and prolonged drop in milk production. Adult cows may also suffer from abortion and reduced fertility. Animals suffering from IBR are highly susceptible to secondary bacterial infections.
Herds with IBR suffer mainly from low-grade problems associated with calf pneumonia, decreased fertility and occasional abortions. More serious problems are seen on farms that have not been exposed to IBR before. Outbreaks with milk-drop and fever in most cows and subsequent abortions and increase in calf pneumonia are seen.