Bob Kahrs: Infectious bovine rhinotracheitis

Infectious bovine rhinotracheitis (IBR) is caused by Bovine Herpes Virus-1. It is a globally distributed respiratory infection of cattle that induces fever, loss of appetite, coughing, rapid breathing, and nasal discharge. It can cause pregnant cattle to abort within 100 days of infection.

It sometimes produces diagnostically significant pus-filled cold-sore-like lesions in the nasal passages. These are found with flashlight-assisted searches and are often overlooked.

Initial IBR infections are usually non-fatal but can become deadly when complicated by stress, secondary bacterial infections including pneumonia, bovine virus diarrhea (BVD) virus, parainfluenza-3 virus, or other infections.

A closely related strain of Bovine herpesvirus-1 is called infectious pustular vulvovaginitis (IPV) virus. IPV virus causes cold-sore-like lesions in the birth canal and on male genitals. IBR and IPV differ largely by their method of transmission and the fact that IPV is usually a localized infection.

Both of these bovine herpesviruses produce persistent latent infections that are carried for years and can be reactivated in healthy cows by stress or steroid injections. Such carrier cattle can initiate outbreaks in susceptible herds that are unvaccinated and free of infection.

IBR is diagnosed by its clinical signs and lesions, by isolation of the virus, or by paired blood samples that lack IBR antibodies early in the infection but are positive three weeks later. Treatment with antibacterials helps control secondary infections.