Infectious diarrhea

Infectious diarrhea may be defined as diarrhea caused by an infection of the digestive system by a bacterium, virus, or parasite that results in frequent bowel motions producing excessive amounts of watery stool.

(Clostridium difficile/C. Diff within large intestine)

Cause/Etiology

This can nearly always be presumed to be infective, although only in a minority of cases is this formally proven. The diarrhea is usually viral in origin, and is mostly caused by Norovirus, Rotavirus, Adenovirus, or Astrovirus.

The most common organisms found are Campylobacter (from animal products), Salmonella (also often from animal foodstuffs), Cryptosporidium (ditto), and Giardia lamblia (lives in water). Shigella dysentery is less common, and usually human in origin. Cholera is rare in Western countries. It is more common in travelers and is usually related to contaminated water (its ultimate source is probably sea water). Escherichia coli is a very common cause of diarrhea, especially Traveler's diarrhea, but it can be difficult to detect using current technology. The types of E. coli vary from area to area and country to country. Clostridium difficile is considered the most common cause of infectious diarrhea in hospitalized patients worldwide.

Viruses, particularly rotavirus, are common in children. (Viral diarrhea is probably over-diagnosed by non-doctors). Norwalk virus can also cause these symptoms.

Toxins and food poisoning can cause diarrhea. These include staphylococcal toxin (often from milk products due to an infected wound in workers), and Bacillus cereus. Often "food poisoning" is really Salmonella infection. Diarrhea can also be caused by ingesting foods that contain indigestible material, for instance, escolar and olestra.

Parasites and worms sometimes cause diarrhea but are often accompanied by weight loss, irritability, rashes or anal itching. The most common is pinworm (mostly a nuisance rather than a severe medical illness). Other worms, such as hookworm, ascaria, and tapeworm are more medically significant and may cause weight loss, anemia, general unwellness and allergy problems. Amoebic dysentery due to Entamoeba histolytica is an important cause of bloody diarrhea in travelers and also sometimes in western countries.

Diagnosis

In more severe cases, or where it is important to find the cause of the illness, stool cultures are instituted.

Among medical inpatients, the presence of fecal leukocytes can predict a "breach in the colonic mucosa (any infectious or inflammatory condition, blood in the stool, or acute vascular insufficiency)":

• sensitivity = 28%
• specificity = 92%

Treatment

With mild cases of acute diarrhea, it is often reasonable to reassure a patient, ensure adequate fluid intake, and wait and see. For children in the developing world, the World Health Organization recommends the use of oral rehydration solution and zinc supplementation for treatment of diarrhea.

Parasites (worms and amoeba) should always be treated with antimicrobial drugs.

Antimotility agents

Loperamide can reduce diarrhea in patients with shigella, but not in patients with traveler's diarrhea due to enterotoxigenic E. coli.

A systematic review of randomized controlled trials found that loperamide may harm children less than 3 years old.

Antisecretory agents

A randomized controlled trial found that racecadotril, an enkephalinase inhibitor, may reduce the volume of watery diarrhea.

Antibiotics

Norfloxacin can reduce the duration of acute diarrhea due to bacterial pathogens. However, norfloxacin may prolong infectivity of patients with salmonella and cause resistant campylobacter.

Prognosis

Acute infectious diarrhea usually lasts 7 days when not treated with antibiotics. It is not uncommon for diarrhea to persist. Diarrhea due to some organisms may persist for years without significant long term illness. More commonly the diarrhea slowly ameliorates but the patient becomes a carrier (harbors the infection without illness). This is often an indication for treatment, especially in food workers or institution workers. In the developing world, infectious diarrhea is a serious, life-threatening illness that results in 4 to 6 million deaths each year, mostly in children.

Salmonella is the most common persistent bacterial organism in humans.