Blastocystis hominis is a single-celled, microscopic intestinal parasite. Whether blastocystis causes illness in people is controversial. The organism is found in both healthy people and those who experience gastrointestinal symptoms. In addition to humans, blastocystis lives in a variety of animals, including amphibians, mammals, and birds. Geographically, the parasite persists in countries all over the world, though developing countries report a higher incidence rate. Some research suggests specific types of blastocystis are more likely to cause symptoms.
Those who experience symptoms from a blastocystis infection may develop gastrointestinal symptoms such as watery diarrhea, vomiting, abdominal pain, nausea, fatigue, loss of appetite, bloating, and excessive gas. Some people also report weight loss, constipation, and anal itching. In some cases, however, even people with blastocystis in their stool may be experiencing symptoms caused by another condition.
Diarrhea associated with blastocystis hominis is usually self-limiting. However, vital fluids, minerals, and salts are lost from the body anytime someone has diarrhea, which can lead to dehydration, especially in children. Signs of dehydration in adults include excessive thirst, little or no urination, dark-colored urine, dry mouth or skin, lightheadedness, dizziness, weakness, and fatigue. In children and infants, symptoms include dry mouth and tongue, sunken eyes, cheeks, or abdomen, crying without tears, fever above 102 F, a dry diaper for three or more hours, and irritability, unresponsiveness, or drowsiness.
Experts believe blastocystis hominis enters the digestive system when a person eats contaminated food or comes into contact with contaminated stool, such as when someone changes a diaper in a daycare setting. The rate at which animal-human, human-animal, and human-human transmission occurs is still unknown. Some studies report that blastocystis hominis infections are more prevalent in individuals living near pets and farm animals.
Those who travel or live in areas where sanitation is poor are more likely to have blastocystis. Individuals with compromised immune systems have a higher incidence as well. Drinking water that is unsafe and handling contaminated animals also raise one's risk of contracting the parasite.
Determining the cause of gastrointestinal symptoms can be challenging. Even if a person has blastocystis hominis in her stool, it doesn't necessarily mean the parasite is causing the symptoms. In addition to asking about recent activities and taking a medical history, a physician can use several tests to identify a parasitic infection. A fecal test looks for parasites in stool. If this test does not indicate the issue, a doctor might order an endoscopy. Doctors rarely use blood tests to look for this parasite, but they can help rule out other causes of gastrointestinal symptoms.
If a person has blastocystis hominis but no symptoms, no treatment is necessary. A person with mild symptoms may not need treatment as the symptoms may clear up on their own. If necessary, antibiotics, combination medications, and antiprotozoal medications can help treat this parasitic infection.
When traveling, people can avoid contracting the parasite by steering clear of contaminated food and avoiding street vendor snacks. When away from home, it is also best to avoid unpasteurized milk and other unpasteurized dairy products, ensure all foods are well-cooked and served hot, and pick meals that don't contain raw fish or meat. Fruit and vegetables that are easy to peel are the best choices, such as avocados, bananas, and oranges. Snacks like flavored ice can also carry the contaminant.
When visiting countries where the water may not be safe, boil water before washing fruits or vegetables or drinking it. Avoid unsterilized water from local sources, including the tap, streams, and wells. Beverages from cans or bottles that are sealed until consumed are generally safe, and iodine-sterilized water is also low risk.
Anyone diagnosed with the parasite should be sure to wash their hands thoroughly and regularly, especially before, during, and after meal preparation and after using the restroom. Alcohol-based hand sanitizer of at least 60% alcohol can also help prevent the spread of infection. Washing hands after using the washroom or changing a diaper is an important step for preventing transmission of a wide range of parasites and bacteria.
Many people have blastocycistis hominis for weeks, months, or years without experiencing any symptoms. Medications are not always effective when someone is treated for the parasite. In some cases, the medicine works on the undiagnosed organism causing symptoms in the gastrointestinal tract. If treatment is not effective and symptoms persist, doctors may investigate other causes.
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