Is there a new E. coli vaccine for cattle?

Either one of two forms of a vaccine recently developed by Agricultural Research Service (ARS) scientists might help to reduce the spread of E. coli O157:H7 bacteria via immunising calves.

Preventing E. coli O157:H7 from proliferating inside cattle helps to limit meat contamination at the packing house and reduces shedding of the microbe into the animals' manure. Manure-borne E. coli can be moved by rainfall into drinking water, which also can end up in irrigation water, and can contaminate fruits, vegetables or other crops, increasing the risk of an outbreak of food-borne illness.

According to ARS staffer Marcia Wood, one form of the vaccine is made up of cells of a strain of E. coli O157:H7 that is lacking a gene known as hha. A second form of the vaccine contains an E. coli strain lacking hha and a second gene, sepB. In either vaccine, the E. coli strain produces a large quantity of immunogenic proteins, which triggers the immune system response that prevents E. coli O157:H7 from successfully colonising cattle intestines.

Holstein calves were immunised in preliminary tests at three months of age with a placebo or either form of the vaccine. Six weeks later, the animals were given a dose of E. coli O157:H7, and, for the next 18 days their manure was tested for evidence of the microbe.

Researchers found that calves receiving either vaccine had reduced or non-detectable levels of E. coli in their manure within only a few days after being inoculated with the bacteria.

The vaccines were developed by research microbiologists Vijay K. Sharma and Thomas A. Casey in their laboratories at the agency's National Animal Disease Centre in Ames, Iowa. A patent is currently being sought for it.