Health

Gastrointestinal Bugs, and How to Keep Them from Spoiling Your Vacation

Travelers Beware!

In the U.S., the usual cause of acute gastroenteritis is viral; therefore, antibiotics have only a small role in treating the infection. However, acute travelers’ diarrhea (ATD), or turista, is a different matter.

When acquired in brief travel to endemic areas like Latin America or Africa, studies show that in the majority of the time, acute diarrhea is bacterial—especially pathogenic, toxin-producing forms of E. coli. Travelers often contract the same bacterial enteric infections that young children in the endemic areas develop; both groups share a naïveté to the pathogens.

Incubation is usually one to three days. Common pathogens include E. coli, Campylobacter, Shigella, and Salmonella. Some cause disease by making toxin in the host, some are non-invasive, others can cause an invasive, bloody diarrhea. Treatment for bacterial gastroenteritis acquired at home or abroad is a bedside decision by the treating physician based on the severity of the illness, the frailty of the patient, and known epidemics, among other things.   

Many practitioners who see patients pre- and post-travel to exotic destinations recommend a short course of self-initiated antibiotics in case ATD occurs. Patients may be given a prescription for medication to carry with them, i.e., a three-day course of a quinolone, such as ciprofloxacin (or a macrolide such as azithromycin for select areas of quinolone resistance in the world such as Southeast Asia). Rapid initiation of antibiotics in travelers will shave a few days off the illness and potentially salvage the trip.  In a very few cases, as in patients with inflammatory bowel disease or in high-stakes diplomatic missions, antibiotics may be given preventatively.  Bismuth may be used as a prophylactic, but it may cause side effects at the therapeutic dose.

Prevention

Prevention is the key for travelers, in terms of food and water precautions. A valuable resource is the Centers for Disease Control website: Salad vegetables washed in local tap water, ice in frozen drinks, and brushing teeth with sink water can transmit infection to the traveler who has not been vigilant.  Patients who are pregnant or immuno-compromised need to be especially careful.  Those taking proton pump inhibitor medications, such as Nexium or Prilosec, also need to be extra-careful, since the suppression of stomach acid reduces food sterilization by the stomach. This may increase the risk of ATD by as high as ten-fold!

Note: Certain areas of the world require far more extensive pre-travel care, including vaccinations, malaria prophylaxis, and the like.  The CDC website has helpful information here, and the International Society for Travel Medicine website can direct you to a certified practitioner of pre-travel care near you.

E. coli and Listeria are bacteria that often make the news in domestic outbreaks.  There are several types of E coli that cause disease in different ways.  E coli 0157:H7, the agent in the 1993 Jack-in-the-Box hamburger epidemic, is notable in that it causes a bloody, invasive, colitic diarrhea as well as an unusual hemolytic uremic syndrome in which renal failure follows the diarrhea.

It is also important to note that antibiotics actually increase the chance for a bad outcome with this strain of E. coli infection and should be avoided if the infection is known.  Risk for this is much higher in ground meat, as in the hamburger epidemic, rather than in steaks and chops, for two reasons.  First, the cow carcasses often become contaminated on the outer surfaces, which in the case of a steak or chop, are exposed to high heat and charred on cooking.  In ground meat, the outside surface is mixed into the middle of the burger or meatloaf, where it is often not cooked as well.  The second reason is that the meat of a steak is from one cow, while the meat in a hamburger may represent hundreds of cows, manifoldly increasing the chance of infection.  This is why, as tasty as a rare hamburger with a red-pink middle is, order it at least medium.  Steaks are lower-risk, but I would never order pinker than medium-rare.   

Listeria is the bug to watch for at picnics, where it can be found in soft cheeses and deli meats. Pregnant women have to be the most careful in avoiding these foods; they should avoid non-pasteurized cheeses altogether.  Potato salad and egg salad sitting out in the sun for hours are also at higher risk for food-borne illness (although the problem is in the potatoes and eggs more than in the mayo).  Outdoor food should be kept chilled until ready to serve, then put away within a few hours.

Giardia lamblia tops the list of intestinal parasitic infections that Americans experience. It may be ingested after contamination from surfaces infected by stool (bathroom handles, changing tables), contaminated drinking water, unintentional swallowing of water while swimming in lakes and ponds, or contact with feces during sex.  It may be acquired in travel to endemic areas, especially in trips a few weeks or longer in duration. Its active form, the trophozoite, has two bilaterally symmetrical nuclei that give the organism the appearance of a face looking back at the microscopist.  Typical symptoms—diarrhea, flatulence, and greasy stool—may take one to three weeks to develop. It is easily treated with a short course of metronidazole, as well as other antibiotics.

home_page_image_giardiaGiardia lamblia. (Source: Centers for Disease Control and Prevention.)

Prevention

Big points to remember in order to avoid acute gastrointestinal infection, especially in travel, are hand hygiene, exclusive use of bottled water in endemic areas, avoiding fruits and vegetables in endemic areas unless they can be cooked or peeled, and extreme care with fresh-water swimming. At those picnics at home, make sure the food remains refrigerated except for the time it needs to be out for serving guests, and if you are going to have hamburgers, make sure they are cooked at least medium.  I highly recommend the CDC website above as a source of both general information and specific information based on your travel destination.

Have fun—and be safe!

 

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