The bacterium Escherichia coli (E. coli) is present in the digestive tracts of animals. Certain strains of E. coli are responsible for diarrhea and a wide variety of porcine diseases. Escherichia coli possesses fimbriae or pili (specialized structures) that allow the bacillus to adhere to the intestinal walls, where it produces toxins that cause fluid and electrolytes to be secreted into the intestinal lumen, which results in diarrhea, dehydration and acidosis. 

The common antigenic types of pili associated with pathogenicity are K88 (F4), K99 (F5), 987P (F6) and F41.¹ Infection in neonates is commonly caused by strains containing the K88 fimbria and, less frequently, the 987P fimbria, whereas postweaning colibacillosis is nearly always due to the K88 strain. Once the bacterium adheres to the villi, it produces one or more enterotoxins (STa, STb, LT), causing hypersecretion followed by profuse watery yellowish diarrhea, with rapid dehydration, acidosis and often death.¹

Confirmation of colibacillosis diagnosis is based on histologic observation of villous colonization. A bacterial culture and a demonstration of K88, K99, 987P or F41u pilus antigens by various immunologic procedures¹ are required.

Therapy includes prompt treatment with antibiotics and restoration of fluid and electrolyte balance. Bacterial antibiotic sensitivity testing is necessary to identify the microorganisms' sensitivity or resistance to antibiotics. Consult your veterinarian before administering antibiotics or vaccines to animals.

Your veterinarian is the best person to talk to for recommendations that are right for your farm.

A strategy that combines reducing the number of E. coli pathogens and increasing resistance in piglets to infection has been shown to be the most effective. The number of pathogens can be controlled through sanitation measures, a proper environment (room temperature, dampness reduction), adequate pens (wire-mesh flooring instead of slatted or solid floors), and quarantine. Resistance can be increased by immunizing sows with a vaccine containing pili (F4, F5, F6) and even enterotoxins (LT) before farrowing so that the piglets' passive immunity improves with colostrum intake.

REFERENCE: 

¹ Merck Veterinary Manual, Third Edition, p. 246

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