Fecal-oral route of transmission

Definition

Fecal-oral transmission involves the acquisition of bacteria, viruses, fungi, and parasites from feces through the mouth, either by ingestion or absorption through the oral mucosa.

Introduction

In fecal-oral transmission, Escherichia coli and other enteric bacteria, viruses, and parasites are transmitted when the feces of a person or animal are inadvertently swallowed. This may occur when hands are not washed after using a toilet, after changing a diaper, after working in dirt or soil, after petting animals, and after cleaning up animal waste. Surfaces in daycare centers and public restrooms may be invisibly covered with such microbes.

Fecal-oral transmission also may occur through eating unwashed or improperly washed raw fruits and vegetables that have been grown in (or have been otherwise in contact with) manure-fertilized soil. For example, one enteric disease outbreak was caused by ingesting unpasteurized cider made from unwashed apples that had fallen to the ground. One study has shown that organic lettuce has one of the highest rates of fecal contamination, more than 22 percent. Fecally contaminated irrigation water is another source of pathogens on raw foods.

Such foods may also become contaminated when harvesters or food preparers handle them with unwashed, stool-contaminated hands. Raw, unpasteurized milk may contain fecal contaminants introduced in the milking process. Food handlers should keep their hands washed with antibacterial soap and should use disposable gloves appropriately. Cutting boards must also be kept disinfected. Cooking food at a high temperature for a sufficient length of time kills these bacteria and parasites.

Fecal-oral transmission may also result from swallowing swimming pool water that has not been sufficiently chlorinated. Similarly, lake or river water may be contaminated with animal feces and should not be consumed. To ensure safe drinking water when camping, water may be boiled, filtered, or chemically treated.

Agents of Fecal-Oral Disease

E. coli contamination in the drinking water of developing countries is the underlying cause of travelers’ diarrhea. Shigella and Yersinia bacteria are also frequently found in contaminated water samples. Norovirus and rotavirus are commonly spread following the changing of diapers, including those of adults. Giardia cysts and Cryptosporidium oocytes in contaminated river water are parasites of fecal-oral transmission.

Gastroenteritis caused by fecal-oral transmission occurs most commonly in the summer. This may be related to increased activities of gardening and farming, animal handling, and recreation in lakes, rivers, and swimming pools. Underlying bacterial causes are most prevalent in the summer, while viral causes are most prevalent in the spring. Underlying bacterial causes are most prevalent in homes and restaurants, while viral causes are most prevalent in housing for the elderly and in hospitals.

Impact

Children and the elderly are most likely to experience severe disease and serious complications as a result of enteric infections because of their fragile nutritional and immune states. Additionally, the rate of fecal-oral transmission is two to four times higher among children in daycare compared with preschool-age children raised at home. However, the increased use of alcohol-containing hand sanitizers and sanitary wipes is gradually compensating for infrequent or inadequate handwashing.

The US Food and Drug Administration and the US Department of Agriculture are concerned with identifying fecal contamination of foods. Hyperspectral fluorescence imaging systems are emerging to scan crops such as strawberries and cantaloupes and poultry carcasses for fecal contamination.

To minimize fecal-oral transmission, one should wash hands thoroughly with an antibacterial soap, not only when hands are visibly soiled but also, and especially, before eating and preparing food. Disposable gloves should be worn by commercial food handlers when preparing uncooked foods such as salads and sandwiches. Gloves should be changed immediately after handling raw meats. Gloves should be discarded upon leaving the workstation, when contaminated by sneezing or coughing, when stained or torn, and after being worn continuously for four hours.

For body fluid contamination of recreational water venues, calculation tables are available to check the concentration of chlorine and the disinfection time necessary to kill Giardia from solid stools and Cryptosporidium from liquid stools (diarrhea) at a pH (acid level) of 7.5 and a temperature of 77° Fahrenheit. Public water parks and pools will soon be able to test for human fecal contamination that is not readily apparent with a commercial kit that uses human secretory immunoglobulin A as an indicator. This form of testing is rapid, specific, and cost-effective.

Bibliography

Centers for Disease Control and Prevention. Morbidity and Mortality Weekly Report: “Communitywide Cryptosporidiosis Outbreak—Utah, 2007.” Journal of the American Medical Association 300 (2008): 1754-1756.

‗‗‗‗‗‗‗. “Cryptosporidiosis Outbreaks Associated with Recreational Water Use—Five States, 2006.” Journal of the American Medical Association 298 (2007): 1507-1509.

Daniel, Charles. "How Diseases Spread Through the Fecal-Oral Route." Verywell Health, 30 Sept. 2024, www.verywellhealth.com/what-is-the-fecal-oral-route-1760046. Accessed 3 Feb. 2025.

‗‗‗‗‗‗‗. “Foodborne Transmission of Hepatitis A—Massachusetts, 2001.” Journal of the American Medical Association 290 (2003): 186-188.

Pajan-Lehpaner, Gordana, and Olivera Petrak. “A One-Year Retrospective Study of Gastroenteritis Outbreaks in Croatia: Incidences and Etiology.” Collegium Antropologicum 33 (2009): 1139-1144.

Van, Rory, et al. “The Effect of Diaper Type and Overclothing on Fecal Contamination in Day-Care Centers.” Journal of the American Medical Association 265 (1991): 1840-1844.