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- Author or Editor: Douglas T. Ensley x
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Objective—To characterize the prevalence of Mycoplasma bovis infection in backgrounding and stocker cattle operations and compare bacteriologic culture with PCR assay for detection of M bovis.
Design—Prospective descriptive study.
Animals—432 calves, 3 to 9 months old, from 9 operations.
Procedures—2 nasal swab specimens were collected from each calf. Swab specimens were evaluated via bacteriologic culture and PCR assay for organisms of the class Mollicutes and M bovis. Culture results were considered negative if no growth occurred within 21 days. Positive results were indicated by characteristic colony formation with PCR assay confirmation. Deoxyribonucleic acid was extracted from 1 swab specimen for direct PCR assay for Mollicutes and M bovis.
Results—Of 432 calves, 374 (87%) had positive results for Mollicutes via PCR assay and 63 (15%) via culture. Seven (2%) calves had positive results for M bovis via PCR assay and 10 (2%) via culture. Prevalence of Mollicutes at the farm level ranged from 54% to 100% via PCR assay and from 0% to 59% via culture. Prevalence of M bovis at the farm level ranged from 0% to 4% via PCR assay and from 0% to 6% via culture. Calves that shed M bovis were significantly more likely to have a fever than were calves that did not shed M bovis.
Conclusions and Clinical Relevance—M bovis was detected at a low level in recently purchased backgrounded and stocker calves in Georgia. Although slightly more infected calves were detected via culture and PCR assay together, PCR assay appeared to accurately identify M bovis at the farm level.
Objective—To evaluate injection-site reactions and serum antibody titers in cattle vaccinated with a clostridial vaccine administered SC or via needle-free transdermal injection.
Animals—Sixteen 11-to 12-month-old Herefords.
Procedures—Cattle in 2 groups were vaccinated on days 0 and 28 with a commercially available multivalent clostridial vaccine administered SC or transdermally Injection sites and serum antibody titers were evaluated at several time points after vaccination. Serum antibody titers against Clostridium perfringens beta toxin, Clostridium novyi alpha toxin, and Clostridium septicum alpha toxin were determined with an ELISA; Clostridium sordellii lethal toxin titers were determined with a toxin neutralization assay.
Results—Firm injection site swellings developed in cattle vaccinated via either route; however, at several observation times, swellings were significantly smaller in cattle vaccinated transdermally. Serum titers against C perfringens beta toxin and C septicum alpha toxin did not differ significantly between groups after vaccination; serum titers against C novyi alpha toxin were not significantly different between groups, except on days 10 and 56, when they were significantly higher in cattle vaccinated SC. Titers against C sordellii lethal toxin were significantly higher in cattle vaccinated SC on several days after vaccination, but titers were not significantly different after day 49.
Conclusions and Clinical Relevance—Transdermal vaccination of cattle resulted in serum antibody titers that were similar to those induced via SC vaccination and caused injection-site reactions that were significantly smaller. Transdermal vaccination may be an effective technique for vaccinating cattle against clostridial diseases while minimizing local reactions that often develop after clostridial vaccination.
Objective—To determine whether administration of 2 doses of a multivalent, modified-live virus vaccine prior to breeding of heifers would provide protection against abortion and fetal infection following exposure of pregnant heifers to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) and cattle with acute bovine herpesvirus 1 (BHV1) infection.
Design—Randomized controlled clinical trial.
Animals—33 crossbred beef heifers, 3 steers, 6 bulls, and 25 calves.
Procedures—20 of 22 vaccinated and 10 of 11 unvaccinated heifers became pregnant and were commingled with 3 steers PI with BVDV type 1a, 1b, or 2 for 56 days beginning 102 days after the second vaccination (administered 30 days after the first vaccination). Eighty days following removal of BVDV-PI steers, heifers were commingled with 3 bulls with acute BHV1 infection for 14 days.
Results—After BVDV exposure, 1 fetus (not evaluated) was aborted by a vaccinated heifer; BVDV was detected in 0 of 19 calves from vaccinated heifers and in all 4 fetuses (aborted after BHV1 exposure) and 6 calves from unvaccinated heifers. Bovine herpesvirus 1 was not detected in any fetus or calf and associated fetal membranes in either treatment group. Vaccinated heifers had longer gestation periods and calves with greater birth weights, weaning weights, average daily gains, and market value at weaning, compared with those for calves born to unvaccinated heifers.
Conclusions and Clinical Relevance—Prebreeding administration of a modified-live virus vaccine to heifers resulted in fewer abortions and BVDV-PI offspring and improved growth and increased market value of weaned calves.