Helping Pigs Resist Edema

Midwest pork producers may someday be able to raise pigs with a natural ability to resist edema disease caused by an intestinal Escherichia coli bacterium. That's welcome news for producers who lose money when pigs get sick from E. coli F18—a strain that doesn't cause disease in humans.

ARS scientists in Ames, Iowa, discovered that resistance and susceptibility to F18 are linked to a gene for a specific blood group. This linkage was concurrently discovered by Peter Vögeli, a scientist with ETH, the technical university of Switzerland in Zürich.

The research began when ARS microbiologist Julia F. Ridpath at the National Animal Disease Center in Ames, Iowa, and veterinarian Brad Bosworth—formerly with ARS and now with Pig Improvement Company (PIC) in Franklin, Kentucky—explored the idea that there could be a genetic basis for some pigs' superior resistance to F18. PIC is a member company of the Biotechnology Research and Development Corporation (BRDC) of Peoria, Illinois, which funded this research.

That NADC work led to a gene marker now incorporated into a test that can be used by breeders to identify resistant pigs. The patented test, validated on over 500 pigs, is a more effective strategy than vaccinating pigs against F18. Vaccines don't always afford sufficient protection, and the cost of vaccines and antibiotics further cuts producers' profits.

Pigs with edema disease are swollen around the eyes. They stagger when they walk and often fall down or just lie on their sides. The characteristic buildup of body fluids is caused by rapid growth of E. coli F18 bacteria in the small intestines of 3- to 14-week-old pigs shortly after weaning. The death rate among pigs with full-blown edema is about 25 percent.

Pigs that are resistant to the disease don't have intestinal receptors, Bosworth says. "The lack of receptors makes it impossible for E. coli F18 bacteria to stick or attach to the intestinal wall. We think the approach of breeding healthier, more disease-resistant pigs will be less costly for producers than increasing the use of antibiotics."

Another way to reduce the problems caused by E. coli F18 bacteria is to feed pigs differently. Susceptible pigs can be fed a diet higher in animal protein, a tactic that prevents the bacteria from taking hold. Weaned pigs should be fed more animal proteins in place of soybean meal.

BRDC has granted PIC an exclusive license for the commercial use of the edema-resistance test worldwide, except in Switzerland.—By Linda Cooke McGraw, Agricultural Research Service Information Staff.

This research is part of Animal Diseases, an ARS National Program described on the World Wide Web at http://www.nps.ars.usda.gov/programs/appvs.htm.

Julia F. Ridpath is in the USDA-ARS Enteric Diseases and Food Research Unit, National Animal Disease Center, P.O. Box 70, Ames, Iowa 50010; phone (515) 663-7372, fax (515) 663-7458.

"Helping Pigs Resist Edema" was published in the July 1999 issue of Agricultural Research magazine.