1. Field of the Invention
The present invention is directed to modified live vaccines for administration to cattle (especially newborn calves) in order to immunize the cattle against virulent wild-type bovine coronavirus infections (enteric and respiratory). The vaccines hereof contain low-passaged bovine coronavirus taken from the group consisting of Type II and Type III bovine coronavirus, and mixtures thereof, and may also contain the known Type I bovine coronavirus. The invention also pertains to a method of treating cattle with hygromycin B in sufficient quantities to suppress shedding of bovine coronavirus in the feces of said cattle.
2. Description of the Prior Art
Bovine coronavirus (BCV) is an important cause of enterocolitis and respiratory tract infections in calves and adult cattle. In some instances, the diseases are referred to as calf diarrhea, calf scours or calf enteritis, and winter dysentery in adult cattle. Heretofore, only one serotype of BCV has been described, and modified live virus vaccines have been prepared by extensive passaging of the virulent virus. Such vaccines are described in U.S. Pat. Nos. 3,839,556, 3,838,004 and 3,869,547.
However, in recent years, the known vaccines have proven to be clinically ineffective against many wild-type BCV infections, and indeed such infections are believed to cause a wide range of disease syndromes.
Another problem inherent in bovine coronavirus infections is the lack of effective treatment of cattle post-infection. A primary vector for spread of such infections results from shedding of virulent BCV in the feces of infected animals. To date, there has been no reported treatment for infected cattle which would suppress or eliminate such shedding.
There is accordingly a real and unsatisfied need in the art for new treatment modalities for cattle at risk for BCV infection, both in terms of a more effective anti-BCV vaccine and a treatment to suppress BCV shedding by infected cattle.