Understanding Colibacillosis: Causes, Symptoms, and Treatments

1. Colibacillosis (E. coli diarrhea) Eman Ahmed 12214 Perihan Mohamed 12231

2. What is Colibacillosis? • Colibacillosis: Infectious disease of man and animals with bacteria called Escherichia coli. Infection can cause severe diarrhea or septicemia. The bacteria can also produce toxins which can affect other parts of the body also. • Colibacillosis is the most common infectious bacterial disease of poultry and is seen in cattle, pigs, goats, and other mammals. It is a common disease that is seen worldwide in places ranging from Egypt, Bangladesh, and Malaysia to America. Causative agent: • Colibacillosis is caused by infection with the bacteria Escherichia coli (E. coli). The bacteria Escherichia coli occur commonly in the intestinal tract of many animals. • Note: The main factor in these infections is inadequate passive immune transfer from the dam to calf (inadequate ingestion or absorption or inadequate antibodies in colostrum), exposure to the pathogen before colostrum was ingested, immediately after birth, inclement weather, use of milk replacers as opposed to whole milk, and poor hygiene.

3. Route of infection: • Transmission of pathogenic E. coli often occurs via fecal–oral transmission. Clinical signs: • Colibacillosis usually is signaled by the appearance of diarrhea: • Severe watery diarrhea caused by enteritis • Lack of appetite and water consumption • Rapid dehydration • Sunken eyes • Stunted growth, inactivity and unresponsiveness • Acidosis (Hyperchloremic acidosis is caused by the loss of too much sodium bicarbonate from the body, which can happen with severe diarrhea) • Morbidity and mortality are very variable depending on which infection/infections the E. coli strain causes in a particular flock of animals. • Colibacillosis signs are nonspecific and vary widely among different hosts.

4. Pathogenesis: • Cow : • o Secondary Infection Omphalitis. • o Arthritis. • o Cystitis. • o Mastitis. • o Pyelonephritis. • Pig : • o Gut Edema. • o Young pigs cause enteric colibacillosis. • Avian : • o Hjarre’s Disease : Colligranuloma. • o Omphalitis • o Peritonitis. • o Salphingitis.

5. E. coli infections in animals and humans cause disease by at least five different general mechanisms: • 1) The first mechanism→ Enterotoxic colibacillosis: • Def. : Secretory small bowel (intestine) diarrhea, stimulated by enterotoxins which are produced by E.coli colonizing the mucosa of small intestine. This condition is an important cause of diarrhea in neonatal animals. • Pathogenesis:The enterotoxins enter the intestinal mucosa and cause the secretion of chloride, with sodium and water following from the crypts. Water is drawn into the intestine to normalize the resultant NaCl, thus the diarrhea is termed secretory. • Affected animals are dehydrated, with a "tucked-up" abdomen. Subsequent to dehydration, the eyes sunken. Animals that die from ETEC infections are often emaciated and have diarrheic feces pasted around their perineum.

6. Microscopically: • Presence of bacteria lining the surface of the enterocytes. Presence of Neutrophils. With some strains of E.coli, there may be necrosis of some villi.

7. Macroscopically: • At necropsy, the small intestine is dilated, flaccid, and filled with translucent, yellow fluid and sometimes gas. Chyle is present in the mesenteric lymphatic vessels similar to animals without enteric disease, indicating that unlike the mal absorptive diseases of SI, absorption proceeds normally in cases of ETEC.

8. 2) The second mechanism→ Enterocyte-adherent E.coli strains: • These strains colonize the surface of the epithelial cells, do not produce recognized enterotoxin, but are associated with villus atrophy. They are not currently known to occur in domestic animals. • 3) The third mechanism→ Enterotoxemic colibacillosis: • Def.:{Edema disease in swine} In this condition a toxin produced by specific strains of E.coli colonizing the small intestine is absorbed and has its pathogenic effect on tissues other than the gut. • Pathogenesis: Pathogenic E. coli colonize and proliferate in the small intestine. Enterotoxins produced by pathogen strains induce the disease, causing damage to small arteries and arterioles. Degenerative angiopathy leads to increased vascular permeability and accumulation of edema at various sites, most notably colon, stomach, small intestine, eyelids, and brain.

9. Macroscopically: • Edema disease is primarily a disease of the vasculature, and gross lesions consist of subcutaneous edema and edema in the submucosa of the stomach, particularly in the glandular cardiac region. The edema fluid is usually gelatinous. The edema may be accompanied by hemorrhage. Fibrin strands may be found in the peritoneal cavity, and serous fluid may be found in both the pleural and peritoneal cavities.

11. Microscopically: • A degenerative angiopathy affecting arteries and arterioles and necrosis of the smooth muscle cells in the tunica media are present.

12. 4) The fourth mechanism→ Septicemic colibacillosis: • It is a common manifestation of disease caused by this organism. The intestine is not necessarily the portal of entry, and there may not alimentary disease. The signs of E.coli septicemia are referable mainly bacteremia, endotoxemia, and the effect of bacterial localization in a variety of tissue spaces throughout the body.

13. 5) The fifth mechanism→ Enteroinvasive colibacillosis: • Enteroinvasive E.coli strains have the capacity to invade the epithelium of the intestine and cause acute exudative enteritis, often endotoxemia, and perhaps terminal septicaemia. Enteroinvasive colibacillosis is apparently rare in domestic animals. • Pathogenesis: • Enteroinvasive E.coli infecting humans and certain other species which have the capacity to invade or to be internalized by surface enterocytes of the small and large intestine, in which they multiply. • Multiplication of the organism within epithelial cells results in local erosion and ulceration, associated with acute inflammation in the mucosa. Diarrhea is described as grey-yellow.

14. Macroscopic lesion: • significant changes were confined to the small intestine: • The mucous membrane is muddy and thickened. • The intraluminal contents from the jejunum to the colon were liquid and yellow. • There is mucosal erosive and ulcers. • Congestion of small intestine.

15. Microscopic lesion: • Blunting of villi (Villous atrophy). • Ulcerative enteritis. • Lengthening of crypt. • Congestion of the blood vessels. • Infiltration of neutrophils and other inflammatory cells .