As with other viruses, antibiotics have no affect on the BRSV infection. However, antibiotic treatment is indicated in attempts to control the secondary bacterial infections. In addition to antibiotics, treatment during an outbreak of the late syndrome in calves (also feedlot calves) would include withholding concentrate feeds or silage for 2-3 days and feeding only enough hay to identify animals that are off feed. Severely affected calves that are unable to drink will need supportive treatments consisting of fluids and electrolytes.
The decision to vaccinate your herd against BRSV should be based upon the susceptibility of the herd. If on testing (serological) the herd is found to be negative to BRSV, you have a very susceptible herd. A vaccination program would be required to raise the resistance of the herd against BRSV. If, on the other hand, a significant number of adults were found to be test-positive, one could assume that the BRSV virus was present in the herd. Chances are that in such herds the heifers kept as replacements will become infected, possibly undergo the mild form of BRSV, and become nonsusceptible to BRSV disease as they age. However, calves shipped from those herds may leave the herd before they become infected; thus they are susceptible to BRSV disease. Herd replacements such as purchased heifers, cows and bulls could be very susceptible to BRSV. Adding them to an infected herd could be a problem for them. Vaccination of herds in which BRSV is known to exist will slow down the spread of the virus through the herd, allowing susceptible animals to get a low exposure rather than a high exposure to the BRSV virus. Unfortunately, maternal antibodies against BRSV passed to the calf via colostrum from vaccinated or infected cows will not protect the calf from BRSV infections. Whether those antibodies will reduce the severity of disease if the calf gets infected, or to what extent the antibodies interfere with vaccination of calves under four months of age has not been determined. Therefore, vaccination of cows against BRSV would not only reduce transmission to susceptible cows and slow down the spread of the virus through the herd, it would also reduce the spread of the disease to the calves. Vaccination of the cow herd provides a barrier. Calves should be vaccinated prior to weaning.
Presently all BRSV vaccines are nonreplicating and can be administered to both pregnant and nonpregnant cattle, regardless of whether they are modified live or killed virus vaccines. Vaccinating animals properly is different than just injecting an animal with a vaccine. Proper BRSV vaccination requires two doses initially, followed by an annual booster of one dose. The initial two doses should be administered at least 21 days apart and started when the animal is over 4 months of age. BRSV vaccine can be purchased alone or in several combinations with other vaccines such as IBR, BVD, PI3, and Lepto-5.
Several Florida ranchers have added BRSV to their vaccination programs, not only to provide a barrier for their herds but also to satisfy customers that have experienced BRSV outbreaks in the newly arrived calves.
The clinical and epidemiological picture in major BRSV outbreaks is quite distinctive; however, the symptoms and lesions noted are generally inadequate for diagnostic purposes. Diagnosis is usually after the fact and must be based on laboratory findings. Because of the difficulty in trying to make a positive field diagnosis, if BRSV is suspected, it is recommended that your veterinarian submit samples for laboratory examination.
Source: E.J. Richey, Extension Veterinarian, College of Veterinary Medicine, Cooperative Extension Service