Vet's Perspective

Feb 28, 2014
by WLJ

E. coli vaccine... are we ready?



The importance of public health cannot be avoided, and researchers have been steadily working on a “One Health” program to ensure that both human and animal health is appropriately managed. A high risk illness caused by the bacterium known as Escherichia coli has been in the news headlines for years. Vaccines have been available for this bacterial disease—but rarely used.

The bacterium causes gastrointestinal disease in humans and cattle, and can even be fatal in severe cases. It has been estimated that one third of E. coli illness cases in humans are related to contaminated beef—other known sources are contaminated produce, crops, and water supply. Herd owners know that lost productivity and food product recalls due to E. coli O157 can cost hundreds of millions of dollars each year—significant economic losses for producers.

Recent research has demonstrated that vaccinating cattle against the E. coli O157 bacterium may decrease human disease cases by approximately 85 percent. These results were obtained by decreasing the amount of bacterial colonies in the top 12 percent of “super shedders.” Among other things, this study out of the University of Glasgow examined the risk of E. coli O157 transmission from cattle to humans.

Bacteria are spread through contact with feces, as well as contaminated food and water supplies. Cattle are a main reservoir for E. coli bacteria. Extremely high numbers of bacteria may be shed at intermittent stages— termed “super shedding.” It is at this period of time that infection is most likely to occur. Vaccines are anticipated to greatly decrease the amount of infective bacteria in the feces of reservoir cattle and therefore the environment. Researchers from Kansas State University have published reports of reduced E. coli levels by 50 percent in the general population to 75 percent in animals shedding high levels of bacteria.

Two vaccines are currently on the market; “Econiche” out of Canada blocks the proteins in E. coli that allow the bacterium to grow and invade the intestinal lining. The American vaccine, “Epitopix SRP” causes a limited uptake of iron by the infective bacteria, thus reducing the colonization capabilities.

Although the public health vector is strongly on board with disease prevention measures, the economic basis for E. coli vaccines within a herd program are still up for debate. It can be a difficult sell to producers as cattle are asymptomatic carriers of the bacteria—and the human population tends to have more of the benefit of vaccination. The vaccines that are currently available have poor reviews; the version in the U.S. is not fully licensed. This is because medicines for veterinary use must show that animal health is improved. Unfortunately, this is problematic because E. coli O157 does not harm cattle and assessing the impact of treatment involves coordination between human and veterinary health practitioners.

Further research with time will show whether the E. coli vaccine truly catches on in the mass market. For now, it is a consideration that some may utilize in upcoming management and prophylactic protocols. — Dr. Genevieve Grammer