If you have an intestinal infection and it’s caused by a parasite, the most likely culprit is Giardia intestinalis—also called Giardia lamblia, or simply giardia. And if it’s giardia (pronounced jee-AR-dee-uh) and you’re a hiker or camper, you probably became infected by drinking from a stream. Up to 80% of all water in the wild contains this protozoan, according to the EPA, as a result of contamination from animal feces. Even if water looks pristine or is running, or if you melt it from snow, it can be contaminated, as can swimming pools, even if chlorinated.
You can also get giardia via contact with an infected person’s feces (for instance, if that person doesn’t wash his hands and then handles food or beverages, or if you handle soiled garments in a day-care center). And, rarely, when their filter systems break down, even municipal water systems in the United States may become contaminated. Pets can also become infected and can spread the parasite to humans.
The symptoms of giardia infection—foul-smelling diarrhea, fatigue, bloating, cramps, gas, nausea—usually take a week or two to begin, but sometimes as long as 25 days. It takes that long for the organism to grow in the intestinal tract and cause symptoms. So you may have trouble pinpointing exactly when you became infected. These symptoms can continue for up to four months or longer. But most infected people never develop symptoms, or get over the infection in one to four weeks without treatment. On the other hand, some people develop a chronic infection, with or without symptoms. Chronic symptoms are very dangerous for people with compromised immune systems.
Giardia infection can be tricky to diagnose, since the cysts are excreted only periodically. You may need to give stool samples on three different days. It is treated with prescription antiparasitic drugs, which are effective but can have unpleasant side effects such as gastrointestinal problems and constipation.
How to prevent giardia
The following advice for avoiding giardia, mostly common sense, will also reduce the risk of many other infections:
- Boil any water you gather when hiking or camping for at least three minutes. Or use a portable purifier (a “filter” may not be good enough). These water purifiers start at about $70. Using only chlorine or iodine won’t protect you from giardia cysts.
- When traveling in the developing world or anywhere sanitation and hygiene are poor, take precautions. Don’t drink tap water unless you boil it, and don’t use ice cubes. Don’t brush your teeth in tap water. Don’t swallow water in the shower or a pool. Drink bottled or canned beverages (carbonated drinks tend to be safest), and be sure you break the seal yourself. Coffee and tea are fine, if the water has been boiled. Bottled wine and beer are fine. Don’t eat anything raw, including salads. Fruit is okay if you wash it with soap and boiled water and peel it yourself.
- Wherever you are, wash your hands well after using the toilet and after handling pets that may be infected or scooping up their feces. If you have young children who attend preschool or day-care centers, giardia is one more reason to wash your hands well after handling soiled diapers or underwear.