Escherichia coli K99 (cattle/calf)

E. coli bacteria are largely normal inhabitants of the large intestine. However, certain strains possess what are known as virulence factors. These strains can cause severe and potentially fatal cases of diarrhea. Of particular importance is the fimbrial or adhesion antigen K 99 (F 5), which enables E. coli to attach itself to the epithelial cells of the intestinal villi. E. coli bacteria also produce so-called enterotoxins. This leads to increased secretion by the enterocytes and, consequently, diarrhea.

In severe cases of E. coli infection, both septicemia and toxemia may occur, leading to corresponding organ damage.

Enterotoxigenic Escherichia coli (ETEC) carry fimbrial antigens, of which F5 (K99) and F41 play the most significant roles in calves. Using these adhesins, the bacteria attach themselves to the small intestinal villi of newborn calves and colonize the small intestine. ETEC produce a heat-stable enterotoxin (STa), which triggers secretory, non-inflammatory diarrhea.

ETEC-induced enteritis primarily affects calves in the first few days of life. The onset is often hyperacute, with profuse, watery diarrhea, rapid dehydration, and the risk of hypovolemic shock. Transmission occurs via the fecal-oral route from contaminated calving and rearing areas.

For diagnosis, it is crucial to differentiate ETEC enteritis from other causes of diarrhea. Detection of the K99 (F5) antigen in feces targets the enteric, fimbria-mediated form of the disease; the septicemic form represents a distinct clinical picture and is not detected by fecal antigen testing.

The Fassisi® BoDia test family (BoDia, BoDia Plus, BoDia + Gia, Fassisi BoDia MPX, Fassisi BoDia Advanced MPX) detects E. coli K99 (F5) in calf feces; in the combination and multiplex variants, it detects this pathogen alongside other diarrhea-causing pathogens.

An overview of the sources used can be found here.