Gastroenteritis

Gastroenteritis is the inflammation of intestines and stomach. The symptoms can include diarrhea, stomach pain, nausea, vomiting, fever or feeling unwell. It could be persistent, acute, or chronic, and can also be classified as infectious or non-infectious.

Diarrhea is defined as the passage of three or more loose or watery stools per day (or more frequent passage of stool than is normal for the individual). Sometimes diarrhea is so severe that a person becomes very ill and loses large amounts of body fluids.

There are three clinical classifications of diarrheal conditions:
• Acute diarrhea, lasting several hours or days
• Acute bloody diarrhea or dysentery
• Persistent diarrhea, lasting 14 days or longer

The three major types of germs that cause gastro are bacteria, viruses and parasites. While most of these are usually harmless, many can cause illness in some situations.

Gastro can also be caused by toxins that some bacteria produce in food (for example Staphylococcus aureus, Clostridium perfringens).

It is quite challenging to establish accurate incidence and prevalence of acute gastroenteritis because of under-reporting of attacks by many patients. Moreover, only 1.5% of stool samples get positive results for a bacterial cause.

Viral infection that affects the stomach and small intestine is called stomach flu. The illness is usually brief, lasting 1 to 3 days. Norovirus and Rotavirus are the most common causes of viral gastroenteritis. Reports suggest that up to twenty-five million cases of acute viral gastroenteritis occur annually in the United States.

The virus enters the stomach and intestine and inflames the lining of these organs. As a result, the stomach and intestine are temporarily unable to perform their usual functions.

The most important causes of bacterial gastroenteritis in Europe have been reported to be enteroaggregative E. coli (EAEC), Campylobacter, and enteropathogenic E. coli. A study in 2012 has concluded that Campylobacter was responsible for more cases of chronic gastroenteritis than Salmonella, with an incidence of 68 vs. 22 cases per 100,000.

Germs that cause gastroenteritis are usually spread by contamination of something that goes in human mouth. This can occur by contact with contaminated objects, including food or water, or by contact with other people who are ill.
Gastroenteritis

Protozoa and Parasites

Some protozoa also cause foodborne illness. Parasites must live on or inside a living host to survive. The most common foodborne parasites are Anisakis simplex, Cryptosporidium parvum, Toxoplasma gondii, Giardia lamblia, and Cyclospora cayetanensis.

Cyclospora was not known to cause human sickness until 1979, when the first cases were reported. Since then fresh produce has been associated with several outbreaks of food borne illness from Cyclospora in US and Canada, cases prolonged gastrointestinal disease in travelers and expatriates associated with southeast Asia and the rise of the immunocompromised population.

Giardia has been identified more than any other pathogen in waterborne disease outbreaks, but there also have been foodborne Giardia outbreaks.

Giardia was first describe by Lambl, who it the name intestinalis. Dogs pick up giardia by drinking water from streams and lakes or other contaminated sources. A person can contract giardia the same way or by failing to wash their hands after cleaning up after a Giardia infected dogs.

Cryptosporidium is also primarily a waterborne pathogen. An estimated 21 percent of waterborne outbreaks from drinking water are due to parasitic agents mainly Giardia and Cryptosporidium.

Waterborne Cryptosporidium oocysts can originate from cattle, swine, horses, deer, chicken, ducks, fish, turtles, guinea pigs, cats dogs or domestic sewage discharge.

Toxoplasma gondii is common in warm blooded animals, including cats, rats, pigs, cows, sheep, deer, chickens and birds.

It can be found in feces and raw meat from these animals.

Anisakis simplex and related worms are found in raw or undercooked seafood. These nematodes parasitizes fish and sea mammals, and thus humans ingest them by eating raw, pickled or smoked fish.

The most common clinical manifestations are those of acute gastric anisakiasis, characterized by epigastric pain, chills, nausea and vomiting within 12-24 of ingestion of parasitized food.

Trichinosis, caused by the parasitic worn Trichinella spiralis and associated with eating undercooked pork, is now relatively rare in the United States.

The parasites has a very broad host range; the major source of human infection are pork or bear meat.

Human infection can vary form subclinical (the majority of cases) to fatal.
Protozoa and Parasites