Association ofEscherichia coli J5-specific serum antibody responses with clinical mastitis outcomefor J5 vaccinate and control dairy cattle

Dairy cattle in two commercial Holstein herds were randomly selected to be vaccinated twice with J5, at approximately 60 days and 28 days before the expected calving date, or to be untreated controls. Based on whether milk production changed following clinical mastitis or whether cows were culled or died within 30 days after onset, 51 mastitis cases were classified as severe or mild. J5-specific antibody responses were evaluated by enzyme-linked immunosorbent assay of all 32 severe and 19 mild cases. The amounts of J5-specific immunoglobulin M (IgM), IgG1, and IgG2 antibodies in sera from the 27 J5 vaccinates were compared with those of the 24 controls. At drying off (before J5 vaccination), all cows had similar amounts of J5-specific antibody. Immediately after calving (approximately 28 days after the second vaccination), J5 vaccinates had significantly higher production of J5-specific IgG1 and IgG2 than controls. When cows were tested following clinical mastitis, none of the three antibody classes differed significantly between the controls and the vaccinates. Vaccinates that contracted Escherichia coli mastitis had 75% less milk loss than controls. The cows that contracted clinical mastitis later in lactation, the unvaccinated controls, and those infected with E. coli had more milk loss following mastitis. The hazards of being culled for all reasons and of being culled for mastitis were significantly lower for J5 vaccinates. Vaccination with J5 was associated with protection against milk production loss and culling following clinical mastitis, and it was also significantly associated with changes in J5-specific IgM, IgG1, and IgG2 antibodies in sera of vaccinated cows. Coliform mastitis is an important disease complex of dairy cows that is associated with intramammary infections (IMI) with any of several organisms, including Escherichia coli and Klebsiella, Enterobacter, and Citrobacter spp. (9, 11, 20, 22). Clinical mastitis (CM), including abnormal milk, necessity for treatment, milk loss, and death of cattle, can result from coliform mastitis (6, 10, 11, 20, 24). Vaccines against the E. coli rough mutant O111:B4 (J5) bacteria have been in use for 15 years (3, 7). The commercially available vaccines are often called J5 core antigen vaccines, but the antigen(s) and mechanism(s) of J5 immunization have not been clearly identified (2, 23). Associations between J5 vaccination of cattle, various measures of clinical severity of CM, and J5-specific antibodies have rarely been reported for naturally occurring cases of CM (2, 17, 19, 23). Use of survival (time-to-event) analysis to evaluate the relationships between J5 vaccination, antibody production, and time until culling or death has recently been reported for the first time (23). Time-to-event analysis as a measure of incidence of disease or any other event of interest precisely accounts for the time at risk for each animal for that event (5). Naturally occurring cases of bovine CM were studied among J5 vaccinates and controls on two commercial United States dairy farms. The hypothesis was that vaccinates would have more J5-specific antibodies, longer survival times, and less milk production loss following coliform mastitis. J5-specific antibodies (immunoglobulin M [IgM], IgG1, IgG2, and the ratio of IgG1 to IgG2) were therefore compared among vaccinates and controls, as were the relationships of antibody to etiologic pathogen, milk production loss, clinical severity, and time until culling or death. These relationships were deemed important because of their practical relevance and were based upon results of previous intramammary E. coli challenge trials (15, 25)