What are bacterial and parasitic gastroenteritis?

Answer: Bacteria and parasites – usually food or water borne – can cause gastroenteritis and lead to vomiting and diarrhea.

Generally, people who hate the stomach flu are also interested in avoiding anything that causes them to be up all night throwing up. Gastroenteritis can also be caused by bacteria and parasites. Although they are less common than the viral form, the illnesses are usually more severe. The good news is, if you are careful, there is a good chance you can go your entire life without getting these.

Some of the bacteria that cause gastroenteritis are salmonella1, campylobacter2, shigella3, and e.coli4. The incubation period for these bacteria usually 1-8 days. These types of gastroenteritis infections can last about 1 week or longer. The sick person usually has a fever in addition to vomiting, diarrhea, and abdominal cramping. Often there is bloody or mucousy diarrhea. E.coli causes bloody diarrhea but frequently no vomiting. Most people recover without treatment but sometimes these infections are life threatening. Infections with nasty strains of E.coli including O157:H7 can cause Hemolytic uremic syndrom (HUS) which leads to kidney failure5. Typhoid fever6 is a life threatening illness caused by Salmonella Typhi and we do have a few hundred cases of it every year in the United States. See your doctor right away if you suspect you have bacterial gastroenteritis or have bloody diarrhea. Bacterial gastroenteritis is often a food borne illnesses (a type of food poisoning). These bacteria come from animal (including human) feces. They can get into your food in the slaughterhouse or via contaminated water used to irrigate plants. If you eat undercooked beef, poultry, eggs, or unpasteurized milk, or if you don’t handle raw meat properly, you are putting yourself at risk. However, outbreaks are often traced to produce that was irrigated with contaminated water. Some of these infections can also be acquired from playing with animals and not washing your hands afterward or getting a gulp of lake water while swimming. When you are sick the bacteria are also present in your feces. The bacteria can be present in your feces for a few weeks after you've recovered. So, they are contagious to other people. This type of food poisoning is contagious!

C. difficile is a bacteria that causes serious diarrhea and can be deadly. It usually strikes people who have been on an antibiotic in recent months and have spent time in a hospital or other healthcare facility. Here is more information about C. difficile from the CDC website.

Parasites such as giaradia7 and cryptosporidium8 also cause gastroenteritis. These infections can be severe and last for weeks. The incubation period of giaradia is 1-2 weeks. The incubation period of cryptosporidium is 2-10 days. Both of these parasites come from feces. These are usually water borne, and commonly transmitted through recreational water activities (swimming pools, hot tubs, lakes, etc.). People can easily get them from a gulp of contaminated water. (Now we all know why the sign at the swimming pool says that everyone must shower before entering the pool.) However, they are occasionally food borne and can be easily transmitted from person to person. There are often outbreaks of giardia and cryptosporidium in day care centers. Chlorine bleach does not kill cryptosporidium!

Cyclospora9 is a single celled parasite that can cause watery diarrhea and sometimes vomiting. The diarrhea can last for weeks or reoccur. The illness strikes 2-14 days after eating a food or water contaminated with the parasite. Foods involved in previous outbreaks have been lettuce, fresh basil, and imported raspberries. Although the parasite is present in stool, it is not usually spread from person to person because the parasite is not in the correct stage when it first comes out in the stool. It has to sit for a week or so before it is ready to infect someone. Cyclospora is difficult to kill and is not killed by chlorine bleach or iodine. The FDA recommends washing produce in clean water and wiping it off with a clean paper towel. They say the wiping helps remove the sticky parasite. Cooking and freezing also kills the parasite.10The antibiotic Bactrim is given to people with a cyclospora infection.

Trichinella11 is another parasite usually acquired by eating undercooked pork or game meats. Symptoms starts 1-2 days after exposure and include vomiting, diarrhea, and abdominal pain. It progresses to more serious symptoms such as eye swelling and muscle pain and lasts for weeks. Trichinella is rare in the United States today because of legislation that prohibits feeding raw meat to hogs. It is not contagious to other people but it requires treatment.

Parasites generally look much scarier than bacteria and viruses. Norovirus and rotavirus are deceptively cute "balls", while giardia is very frightening. For more information about just about EVERY organism (bacteria, parasite, worm, or virus) that might make you throw up, check out the FDA's "Bad Bug Book". For information on other types of terrifying parasites that may or may not involve gastroenteritis go to the Animal Planet Monsters Inside Me web site.

--Annie Pryor, Ph.D.

Viewer Comments

I had cryptosporidium

I contracted this parasite in January 2012. It was so scary. I felt fine all day, went out to dinner and was hungry. About 20 minutes after dinner the d* started. Then I v* and kept having d* so I told my fiance (now husband) to take me to the ER because I knew something was terribly wrong. They thought it was food poisoning or the sv but I didn't agree. I was admitted because I had a fever and kept having liquid d* and extreme nausea. I spent 3 nights at the hospital while they ran tests. I only v* twice but it was horrific. On the 4th day my results came back positive for cryptosporidiosis. I had to take strong antibiotics for 2 weeks and the d* lasted on and off for a few weeks. The health department called me to inquire how I could have contracted it. We never knew the source. I think I picked it up at Bikram yoga. Two days after I came home from the hospital my fiance got the sv!! I wasn't with him because we lived apart doing long distance. I think he picked it up from visiting me in the hospital.


I had Ecoli

I notice ecoli is briefly mentioned and just wanted to inform you that vomiting is not a typical symptom of this. I had a severe case of e.coli in 2002 and nearly died... The hallmark symptom is bloody diarrhea and severe abdominal pain. (It started as brown diarrhea, though.) I had no nausea or vomiting which is what helped them pinpoint my diagnosis. And by "bloody diarrhea" I mean it looked like V8 Vegetable Juice with chunks... For 12 days. I went into kidney failure and now I have CKD (chronic kidney disease) for the rest of my life. I hear a lot of people say they are nauseous and that they hope it isn't ecoli... So I just wanted to clarify that :)


1. http://www.cdc.gov/salmonella/

2. http://www.cdc.gov/nczved/divisions/dfbmd/diseases/campylobacter/

3. http://www.cdc.gov/nczved/divisions/dfbmd/diseases/shigellosis/



6 http://www.cdc.gov/nczved/divisions/dfbmd/diseases/typhoid_fever/


8. http://www.cdc.gov/crypto/

9 http://www.cdc.gov/parasites/cyclosporiasis/

10. http://www.m.webmd.com/food-recipes/news/20130725/cyclospora-parasite-can-taint-fresh-produce?page=3

11 http://www.cdc.gov/parasites/trichinellosis/index.html