Vaccinating a large herd of beef cattle is a tedious but necessary process, involving a coordinated effort to ensure every animal is treated adequately and efficiently. But new developments in edible vaccine technology could make the painstaking procedure as uneventful as cattle chewing their cud.

Ontario Veterinary College Prof. Patricia Shewen and research associate Douglas Hodgins, Department of Pathobiology, have teamed up with researchers in the College of Biological Science and the Ontario Agricultural College to create a vaccine disguised as alfalfa, a common feed supplement in the bovine diet.

"The ideal approach in vaccination is to introduce the organism that causes disease through its natural route of entry into the body," says Shewen. "This way the body develops a barrier of protection in the most ideal location - where the organism would normally produce disease."

One particularly harmful disease that affects cattle - shipping fever - involves infection of the lungs and lower respiratory tract by an organism that resides in the tonsils. Following natural exposure, an immune response to this bacterium - Mannheimia haemolytica - is generally not powerful enough to ensure future protection against re-infection.

The researchers hope they can vaccinate against shipping fever by exposing the tonsils to certain proteins called antigens. To accomplish this, the scientists have genetically modified alfalfa to produce the antigens within its greenery. Now, they're feeding this alfalfa to unvaccinated calves to see if they will develop immunity to the disease in their tonsils.

"We're taking advantage of the fact that ruminants ruminate," says Shewen. Not only do the tonsils get exposed to the antigens when the calf first swallows the alfalfa, but they get re-exposed every time the calf brings the food back up - as they normally would when chewing their cud.

If the researchers are successful, they'll work on developing other disease vaccines in new plants.

Other University of Guelph researchers working on this project include Prof. Reggie Lo and research associate Raymond Lee in the Department of Microbiology and Prof. Judy Strommer and research associate Asma Ziauddin in the Department of Plant Agriculture.

This research is sponsored by the Natural Sciences and Engineering Research Council and the Ontario Ministry of Agriculture and Food.