Signs and symptoms that might be associated with blastocystosis include:
- Abdominal cramps
- Excessive gas (flatulence)
- Anal itching
- Loss of appetite
- Weight loss
When to see a doctor
See your doctor if you have signs and symptoms, such as diarrhea or cramps, that last longer than three days.
Once thought to be a harmless yeast, blastocystis is a parasite, a microscopic single-celled organism (protozoan). Many protozoans inhabit your gastrointestinal tract and are harmless or even helpful; others cause disease.
Whether blastocystis is the type of protozoa that causes disease is controversial. While many people who carry blastocystis have no signs or symptoms, the organism is also found in others who have diarrhea and other gastrointestinal problems. Because blastocystis often appears with other organisms, experts aren't sure whether it causes disease on its own or is an innocent bystander in this setting.
It's also possible that some people may be carriers of blastocystis and don't exhibit any signs or symptoms of infection, while other people are more susceptible to infection.
Many types of protozoans get into the intestinal tract through oral-fecal contact, such as occurs when a person doesn't wash his or her hands thoroughly after using the toilet before preparing food. No one knows for certain how blastocystis is transmitted, but experts suspect it's through oral-fecal contact. Experts do know that the prevalence of blastocystis increases in places with inadequate sanitation and poor personal hygiene.
Blastocystosis is common, and anyone can get the infection. You may be at higher risk if you travel or live where sanitation is inadequate or where the water may not be safe.
If you have diarrhea associated with blastocystis, it's likely to be self-limiting. However, anytime you have diarrhea, you lose vital fluids, salts and minerals, which can lead to dehydration. Children are especially vulnerable to dehydration.
You may be able to prevent blastocystis or other gastrointestinal infection by taking a number of precautions while traveling in high-risk countries.
Watch what you eat
The general rule of thumb is this: If you can't boil it, cook it or peel it — forget it. Unfortunately, most travelers don't stick to these guidelines all of the time. Remember these tips:
- Avoid food from street vendors.
- Avoid unpasteurized milk and dairy products, including ice cream.
- Avoid raw or undercooked meat, fish and shellfish.
- Steer clear of moist food at room temperature, such as sauces and buffet offerings.
- Eat foods that are well cooked and served hot.
- Munch on dry foods — like breads — and foods high in sugar, such as jellies and syrups.
- Stick to fruits and vegetables that you can peel yourself, such as bananas, oranges and avocados. Stay away from salads and unpeelable fruits, such as grapes and berries.
Don't drink the water
When visiting high-risk countries, keep the following tips in mind:
- Avoid unsterilized water — from tap, well or stream. If you need to consume local water, boil it for at least three minutes and then let it cool to room temperature.
- Avoid ice cubes or fruit juices made with tap water.
- Beware of sliced fruit that may have been washed in contaminated water.
- Don't swim in water that may be contaminated.
- Keep your mouth closed while showering.
- Feel free to drink canned or bottled drinks in their original containers — including water, carbonated beverages, beer or wine — as long as you break the seals on the containers yourself. Wipe off any can or bottle before drinking or pouring.
- Use bottled water to brush your teeth.
- Use bottled or boiled water to mix baby formula.
- Make sure hot beverages, such as coffee or tea, are steaming hot.
If it's not possible to buy bottled water or boil your water, bring some means to purify water: Consider a water-filter pump with a microstrainer filter that can filter out small microorganisms. Look in camping stores for a filter that is certified by the National Science Foundation.
Another approach is to chemically disinfect water with iodine or chlorine. Iodine tends to be more effective, but reserve it for short trips, because too much iodine can be harmful to your body. You can purchase iodine tablets or crystals at camping stores and pharmacies. Be sure to carefully follow the directions.
Take precautions against passing a parasite to others
If you have blastocystis or another gastrointestinal infection, good personal hygiene will help keep you from spreading the infection to others:
- Wash hands with soap and water frequently, especially after using the toilet and before handling food. Rub soapy, wet hands together for at least 20 seconds before rinsing. If soap and water aren't available, use an alcohol-based hand sanitizer.
- Wash hands well after changing a diaper, especially if you work in a child care center, even if you wear gloves.