Preweaned heifer management on US dairy operations: Part IV. Factors associated with the presence of Escherichia coli O157 in preweaned dairy heifers.

Dairy calves shed pathogenic Escherichia coli O157 (O157) in feces and are a potential route of exposure for human infections. As part of the National Animal Health Monitoring System's (NAHMS) Dairy 2014 study, we evaluated farm, animal, and environmental factors associated with O157 presence in dairy heifer calves. For this O157 study, calves were enrolled from 100 dairy operations in 13 states. Each operation collected data from calves from birth to weaning over an 18-mo period. A single fecal sample was collected from 487 calves in western states and from 871 calves in eastern states (n = 1,358 total), and O157 was detected in 2.5% (n = 34) of fecal samples. Descriptive statistics and univariable screening were used to determine which farm practices, environmental factors, and calf health measures were associated with O157 detection. Multilevel logistic models, controlling for dairy operation, were created using backward elimination of screened variables. The final O157 main effects model included variables for source of colostrum, temperature-humidity index (THI), and serum IgG concentration. Higher serum IgG was associated with lower odds of O157 shedding, whereas calves fed colostrum from their own dam had higher odds of O157 shedding than calves fed colostrum from pooled sources. Interaction models showed that THI level modified the effect of colostrum source on O157 shedding; calves with a THI indicative of heat stress had a significantly increased presence of O157 when fed colostrum from a first-lactation dam. The THI level also modified the effects of serum IgG. Calves with thermoneutral or heat stress THI values had increased presence of O157 with poor (<10 g/L) or adequate (10-15 g/L) serum IgG levels compared with those having excellent (≥15 g/L) serum IgG levels. These results highlight factors that influence the presence of O157 in preweaned dairy heifer calves and may be used to guide practices that mitigate shedding through improved animal husbandry.

Efficacy of oral and parenteral routes of Mycobacterium bovis bacille Calmette-Guerin vaccination against experimental bovine tuberculosis in white-tailed deer (Odocoileus virginianus): a feasibility study.

We investigated the efficacy of oral and parenteral Mycobacterium bovis bacille Calmette-Guerin Danish strain 1331 (BCG) in its ability to protect white-tailed deer (Odocoileus virginianus) against disease caused by M. bovis infection. Twenty-two white-tailed deer were divided into four groups. One group (n=5) received 10(9) colony-forming units (cfu) BCG via a lipid-formulated oral bait; one group (n=5) received 10(9) cfu BCG in culture directly to the oropharynx, one group (n=6) was vaccinated with 10(6) cfu BCG subcutaneously, and one group served as a control and received culture media directly to the oropharynx (n=6). All animals were challenged 3 mo after vaccination. Five months postchallenge the animals were examined for lesions. Results indicate that both oral forms of BCG and parenterally administered BCG offered significant protection against M. bovis challenge as compared to controls. This study suggests that oral BCG vaccination may be a feasible means of controlling bovine tuberculosis in wild white-tailed deer populations.