Infectious bovine rhinotracheitis (IBR) is caused by bovine herpesvirus-1 and is known to be part of the bovine respiratory disease (BRD) complex. (1) Bovine herpesvirus-1 has many different presentations, the most common presentation in feedlots is respiratory symptoms (IBR) but infectious pustular vulvovaginitis (IPV), abortion, pink-eye like symptoms (inflammation and scarring of the eye), and various other lesions can occur in cow-calf operations. (2) IBR is more likely to occur under intensively managed systems like feedlots than cattle on pasture but it is still an important an important disease for cow-calf producers to be aware of. (1).
The symptoms of IBR are varied and can easily be confused with other diseases. The disease caused by IBR is generally not life threatening but becomes serious when a secondary bacterial infection is established (3). The incubation period is normally between 2-7 days (1). With mild cases you might see clear nasal discharge and a slight increase in body temperature. With more severe cases you may see a high fever (40-42ºC, normal for cattle is 38-39ºC) along with depression, decreased appetite, an increased respiratory rate and increased salivation. A nasal discharge is typically present and is generally yellow or white; the nostrils may become red and inflamed. (1). Conjunctivitis (inflammation of the inner eyelids) with a clear watery discharge from the eyes and corneal opacity (similiar to pink eye scarring) may also be seen (1,3). Quite often these infections will develop into pneumonia due to a secondary bacterial infection. If a secondary bacterial infection does not occur recovery generally occurs within 4-5 days of the appearance of symptoms. Cattle are much more susceptible to IBR during their first couple of weeks in the feedlot or as young calves on the cow calf operation (1).
Infection with bovine herpesvirus-1 occurs by the respiratory and genital routes. The virus replicates in the upper respiratory tract and genital epithelial surfaces and is then spread by respiratory and genital secretions. The virus infects local nerve endings and a lifelong infection is established (1). Like other herpes virus infections, once an infection has been established the animal has a latent infection (asymptomatic the majority of the time). The virus can be reactivated at any time, with or without symptoms, and can be spread to other animals when reactivated (1). Stress is one of the main factors that causes the virus to reactivate.When cattle are moved to a feedlot they are under a lot of stress and the virus would reactivate and be infectious to the surrounding animals, it could potentially cause clinical signs in the carriers and the newly infected animals.The virus can spread by direct contact with an infected animal or by sharing a water source, feed bunk etc. Aerosol droplets can also be infective. These would be the most common ways the virus is spread in a feedlot situation.(1) The virus is typically spread by breeding in cow calf operations with the infected calves bringing the virus to the feedlot.