The effects of simultaneous foot-and-mouth disease and Escherichia coli vaccination on the immunity of pregnant cows and their calves.

Fighting against infectious diseases with almost 18 million cattle spread over a wide geographical area is troublesome economically and physically. The administration of different vaccines simultaneously during the foot-and-mouth disease (FMD) vaccination campaign will help reduce both the vaccine stress of animals and the field veterinarians' workload. Diarrhea due to Escherichia coli (E. coli) is a significant problem and a major cause of mortality in calves, and thus, simultaneous application of FMD and E. coli vaccines to dams would prove efficient in field conditions. This study aimed to investigate the effect of simultaneous administration of four different locally produced gel and oil adjuvant inactivated E. coli vaccines with locally produced oil adjuvant inactivated FMD vaccine on neutralizing antibody levels and the properties of the antibodies in late-term pregnant dams and their calves. For this purpose, seven to eight-month-old pregnant dams (n = 146) were divided into two main groups to receive two doses (single and booster), or only single dose (no booster). FMD neutralizing antibody titers were evaluated by a virus neutralization test against serotype A, O, and Asia1. In addition, the properties of antibodies against serotype A were assessed by isotype and avidity ELISAs. E. coli antibodies were measured by the hemagglutination inhibition test. Results of the study revealed no safety problems in any dams after the vaccinations. On day 42, calves of the dams vaccinated simultaneously had higher neutralizing antibody titers against three serotypes than the calves of only FMD vaccinated dams. IgG1/IgG2 ratio was higher in single-dose groups than booster-dose groups against serotype A in calves. The avidity index was detected over the threshold value (24.5%). A positive correlation was found in the transmission of maternal antibodies from mothers to calves in simultaneous administration groups. In conclusion, during the FMD vaccine campaigns, FMD and E. coli vaccines can be simultaneously applied to dams in the 7th and 8th months of gestation. Results of this study has led to the inclusion of simultaneous application of FMD and E. coli vaccines in the 'Animal Disease and Animal Movement Control Program-2018' and these two vaccines have been applied in the field ever since as a solution for field veterinarians to save time and labor during vaccination.