Clinical Case Review: Infectious Bovine Rhinotracheitis and Other Disease Manifestations of Bovine Herpesvirus-1 By: Jose Valles and Lisa Taylor, Production Animal Consultation
Infectious bovine rhinotracheitis (IBR) is a viral infection that affects the upper respiratory tract of infected animals. It was first recognized in the western United Stated during the 1950s. IBR was one of the first viral infections linked with bovine respiratory disease (BRD), and it is one of many factors that can contribute to shipping fever. This acute viral infection affects beef and dairy cattle and other wild ruminants worldwide. While IBR is common in U.S. cattle herds, some European countries have successfully eradicated the disease. Outbreaks of this particular disease can result in significant economic losses for cattle operations. IBR is caused by bovine herpesvirus-1 (BHV-1), a member of the Herpesviridae family. In addition to IBR, this highly contagious virus causes conjunctivitis; infectious pustular vulvovaginitis (IPV) and infectious pustular balanoposthitis (IPB); abortion; and encephalitis. BHV-1 infection in young calves can result in systemic infection, leading to death. The disease associated with BHV-1 infection depends on the virus route of infection, strain, and dose, as well as environmental factors and the animal’s age and immune function. IBR is common in feedlot settings, while IPV, IPB, and abortion are more common in breeding herds. IBR infection can cause immunosuppression, making animals more susceptible to BRD. Transmission of IBR occurs through saliva, nasal secretions, or contaminated aerosols. When affecting other organ systems, BHV-1 can be transmitted in utero, at birth, or venereally. Incubation for the virus is 2-6 days. Without complicating bacterial infections, the animal will usually recover 4-5 days after the onset of clinical signs. The virus becomes latent in the animal’s nervous tissue and can be reactivated by various factors including calving, stress, transportation, corticosteroid treatment, and weather changes. After reactivation, the animal usually does not display clinical signs, but it still sheds the virus, spreading disease to susceptible herd mates. BHV-1 can affect cattle of all ages and breeds. Calves 6 26 pacdvms.com
months of age and older tend to be more susceptible because their passive immunity is fading. Disease outbreaks generally remain active for 14 to 28 days and are more likely to occur when cattle are commingled and confined. Consequently, IBR outbreaks are common in feedlots in the fall and winter. Mortality due to IBR is not common unless complicated by secondary infection. Clinical signs of animals infected with IBR may include coughing, depression, fever, inflamed nose and muzzle, labored or rapid breathing, loss of appetite, nasal discharge, open mouth breathing, reduced milk yield, salivation, and weight loss. These symptoms may vary when a secondary infection is present. Cattle may also present symptoms of conjunctivitis including red eyes, ocular discharge, and, in some cases, corneal opacity. In cases of IPV, clinical signs may include elevated tail head, elevated temperature, frequent urination, lesions on the vulvar and vaginal lining, tail switching, vulvar discharge, and vulvar inflammation. Similarly, symptoms of IPB may include decreased libido, an inflamed prepuce or penis, and pustular lesions. Abortion associated with BHV-1 infection is most likely during the second half of gestation. Recommended medical examination for cattle suspect of IBR includes lung score, rectal temperature, visual clinical signs, feed intake, water consumption, and movement. Suspect animals should be closely monitored and provided Figure 1: Necrotic lesion found in mid-trachea during post-mortem exam consistent with IBR infection.
