Vaccination of calves at day of birth with attenuated vaccines against bovine respiratory syncytial virus, bovine parainfluenza type 3 virus and respiratory bovine coronavirus

ABSTRACT

/ Summary Bovine Respiratory Disease (BRD) is a major cause of calfhood mortality. Bovine Respiratory Syncytial Virus (BRSV), Bovine Parainfluenza 3 Virus (BPIV3), Bovine Herpes Virus-1 (BHV-1), and Bovine Corona Virus (BCV) are major pathogens in BRD outbreaks. The importance of early protection of newborn calves is undoubted. The BRD vaccines licensed in Europe can be applied from one or two weeks of age onwards. We have investigated the safety and immunity of a commercial intranasal live BRSV-BPIV3 combination vaccine and a live-attenuated BCV vaccine (in development) in calves at day of birth. In the safety study the calves were revaccinated two weeks after the first vaccination. In the efficacy studies, the calves were experimentally infected with field isolates six days (BRSV, study #2), seven days (BPIV3, study #3) and five days (BCV, study #4), post vaccination. Animals were monitored for any adverse effects of the vaccination and clinical disease following the challenge infection. Samples were collected and tested for RNA specific for the respective vaccine and challenge viruses. Fourteen days after the BRSV challenge infection, the animals in study #2 were euthanized and a necropsy was performed. The frequency and degree of symptoms of abnormal health observed in the safety study, were comparable to those observed in older animals after vaccination with the same vaccines. Mild to moderate signs of upper respiratory tract disease (URTD) were the predominant clinical signs after challenge infection. The average scores in the vaccinated groups were lower in the control groups, but the differences did not reach significance. Moreover, the virus load in nasal swabs was significantly lower in the vaccinated group as was the BCV virus load in rectal swab samples taken from the vaccinated animals. From the four studies it can be concluded that the vaccines used in these studies can be applied from the day of birth onwards.