Kansas State researchers find cattle vaccine works to reduce E. coli O157:H7 in a large-scale feedlot setting
Posted: August 7th, 2012 - 5:03am by Doug Powell
A commercial vaccine for cattle can effectively reduce levels of E. coli by more than 50 percent, a Kansas State University study has found. The vaccine is also effective using two doses instead of the recommended three doses, which can help cut costs for the beef industry.
David Renter, associate professor of epidemiology, is the principal investigator on a project that researched the effectiveness of products used to prevent the shedding of E. coli O157:H7 in cattle. The research appears in a recent online version of the journal Vaccine and helps improve current preventative methods for addressing food safety concerns.
While E. coli O157:H7 does not affect cattle, it causes foodborne disease in humans. Vaccines and other products may be given to cattle to help prevent the spread of the bacteria.
"We wanted to test how well these products work to control E. coli O157:H7 in a commercial feedlot with a large population of cattle that were fed in the summer and may be expected to have a high level of E. coli O157:H7," Renter said.
Other Kansas State University researchers involved include T.G. Nagaraja, university distinguished professor of microbiology; Nora Bello, assistant professor of statistics; Charley Cull, doctoral student in pathobiology, Oakland, Neb.; and Zachary Paddock, doctoral student in pathobiology, Manhattan. Abram Babcock, an August 2010 Kansas State University doctoral graduate, also was involved in the research.
Using a commercial feedlot setting, the researchers studied more than 17,000 cattle during an 85-day period. They studied two products: a vaccine and a low-dose direct-fed microbial.
"What's unique about this study is the number of animals we used, the research setting and that we used commercial products in the way that any cattle producer could use them," Renter said. "We didn't want it to be any different than the way somebody would use the products in a commercial feedlot."
The researchers found that the vaccine reduced the number of cattle that were shedding E. coli O157:H7 in feces by more than 50 percent. E. coli shedding was reduced by more than 75 percent among cattle that were high shedders of E. coli. While the vaccine label suggests that it is given in three doses, the researchers found that two doses of the vaccine significantly reduced E. coli.
"Showing that level of efficacy with two doses is really important because a shift to two doses from three could significantly cut costs for the beef industry," Renter said. "In terms of logistics, it can be difficult for commercial feedlot production systems to vaccinate animals three times. Both of these benefits help when considering how the vaccine can be adopted and implemented in the industry."
The researchers also discovered that the low-dose direct-fed microbial product did not work as well as the vaccine. Renter said while the study used a lower dose of the direct-fed microbial and could find no evidence that it reduced E. coli shredding, it is possible that the direct-fed microbial product is more effective at a higher dose.
"This vaccine is an option for reducing E. coli," Renter said. "We have shown that this vaccine works and that it is a tool that could be adopted in the industry."
The research was supported as part of a three-year $1 million grant from the U.S. Department of Agriculture. Nagaraja and Renter are involved in several other studies on E. coli O157 and other types of E. coli closely related to O157, including research associated with the $25 million coordinated agricultural program, or CAP, grant with the University of Nebraska Lincoln and several other universities. That five-year grant is supported by the USDA's National Institute of Food and Agriculture.
Efficacy of a vaccine and a direct-fed microbial against fecal shedding of Escherichia coli O157:H7 in a randomized pen-level field trial of commercial feedlot cattle.
Cull CA, Paddock ZD, Nagaraja TG, Bello NM, Babcock AH, Renter DG
Our primary objective was to determine the efficacy of a siderophore receptor and porin proteins-based vaccine (VAC) and a Lactobacillus acidophilus-based direct-fed microbial (DFM) against fecal shedding of Escherichia coli O157:H7 in commercial feedlot cattle fed a corn grain-based diet with 25% distiller's grains. Cattle projected to be on a finishing diet during the summer were randomly allocated into 40 study pens within ten blocks based on allocation dates. Blocks were complete; each of the four pens within a block was randomly assigned one treatment: control, VAC, DFM, or VAC+DFM. The DFM was fed (10(6)CFU/animal/day of Lactobacillus) throughout the study periods (84-88 days) and cattle were vaccinated at enrollment and again three weeks later. Fresh fecal samples (30/pen) from pen floors were collected weekly for four consecutive weeks (study days 52-77). Two concurrent culture procedures were used to enable estimates of E. coli O157:H7 shedding prevalence and prevalence of high shedders. From 4800 total samples, 1522 (31.7%) were positive for E. coli O157:H7 and 169 (3.5%) were considered high shedders. Pen-level linear mixed models were used for data analyses. There were no significant interactions among treatments and time of sampling. However, vaccinated pens had lower (P<0.01) overall prevalence of E. coli O157:H7 (model-adjusted mean ±SEM=17.4±3.95%) and lower (P<0.01) prevalence of high shedders (0.95±0.26%) than unvaccinated pens (37.0±6.32% and 4.19±0.81%, respectively). There was no evidence of a DFM effect on either measure of E. coli O157:H7 shedding. Results indicate that a two-dose regimen of the vaccine significantly reduces fecal prevalence of E. coli O157:H7 (vaccine efficacy of 53.0%) and prevalence of E. coli O157:H7 high shedders (vaccine efficacy of 77.3%) in commercial feedlot cattle reared in the summer on a finishing diet with 25% distiller's grains.