Enteric colibacillosis is a common disease of nursing and weanling pigs caused by colonization of the small intestine by enterotoxigenic strains of Escherichia coli (ETEC). Colonization of the small intestine by ETEC strains typically results in severe, watery diarrhea and dehydration. Disease is typically confirmed via a combination of lesion assessment, cultural confirmation, and genotyping of bacterial isolates.
Etiology and Pathogenesis of Enteric Colibacillosis in Pigs
Certain strains of E coli possess fimbriae that allow them to adhere to or colonize the absorptive epithelial cells of the jejunum and ileum. The common antigenic types of fimbriae associated with pathogenicity are F4 (K88), F5 (K99), F6 (987P), F18, and F41. Pathogenic strains produce various combinations of enterotoxins that act locally to induce fluid and electrolyte secretion into the intestinal lumen, resulting in diarrhea, dehydration, and metabolic acidosis. Neonatal colibacillosis is commonly caused by F4 and, to a lesser extent, F5, F6, and F41 strains. Postweaning colibacillosis is most often associated with the F4 or F18 strains. There is also a genetic susceptibility component, because not all pigs express receptors for all fimbrial adhesins.
Clinical Findings of Enteric Colibacillosis in Pigs
Profuse watery diarrhea with rapid dehydration, acidosis, and death are common clinical signs in pigs with enteric colibacillosis. Rarely, pigs collapse and die before diarrhea begins.
Lesions of Enteric Colibacillosis in Pigs
Dehydration and distention of the small intestine, with yellowish, watery to slightly mucoid fluid, are characteristic. The colon often contains similar fluid. The stomach is typically dilated and can be full of feed. Pigs dying suddenly can have patchy cutaneous erythema. Histologically, the villi are usually of normal length and have many small bacterial rods adhered to the absorptive enterocytes (see ).
Enterotoxigenic Escherichia coli in a piglet. Note the numerous short rods, typical of E coli, adhering closely to the jejunal epithelial surface (arrowheads). H&E stain; scale bar = 100 mcm.
Courtesy of Dr. Eric R. Burrough.
Diagnosis of Enteric Colibacillosis in Pigs
Confirmation via culture with or without genotyping
Histological evaluation
Confirmation of enteric colibacillosis is based on histological observation of coliform colonization of small intestinal brush borders and isolation of the organism from the small intestine. F4 and F18 strains are strongly hemolytic on blood agar; however, not all hemolytic E coli are pathogens. Genotyping PCR assays are available to detect fimbrial type and the presence of enterotoxin genes.
Treatment and Control of Enteric Colibacillosis in Pigs
Antimicrobial treatment based on results of minimum inhibitory concentration testing
Vaccination
Treatment for enteric colibacillosis includes prompt administration of antimicrobials and restoration of fluid and electrolyte balance. Bacterial antimicrobial susceptibility (minimum inhibitory concentration) testing is helpful to identify effective medication, because many strains are resistant to multiple antimicrobials.
Prevention of enteric colibacillosis includes minimizing predisposing factors (eg, dampness and cold), improving sanitation, and vaccinating. Gestating sows can be vaccinated with pilus-specific vaccines, and weaned pigs can be treated with live attenuated F4 and F18 strains lacking enterotoxins. Pigs lacking receptors for F4 or F18 E coli are naturally resistant to disease associated with these strains.
Key Points
Pathogenic Escherichia coli have fimbriae for attachment and produce one or more enterotoxins.
Pigs with enterotoxigenic E coli develop a secretory diarrhea and dehydrate rapidly.
Because many E coli are commensal organisms, genotyping of isolates is helpful to confirm pathogenic potential.
For More Information
Dubreuil JD, Isaacson RE, Schifferli DM. Animal enterotoxigenic Escherichia coli. EcoSal Plus. 2016;7(1).
Luppi A, Martelli P. Escherichia. In: Zimmerman JJ, Burrough ER, Karriker LA, Schwartz KJ, Zhang J, eds. Diseases of Swine. 12th ed. John Wiley & Sons Inc; 2026:957-996.
