Giardia Infection
Introduction
Giardia infection is an intestinal infection marked by stomach cramps, bloating, nausea and bouts of watery diarrhea. Giardia infection is caused by the parasite Giardia intestinalis (also called Giardia lamblia). The parasite is found worldwide but is especially prevalent in countries with poor sanitation and unsafe water, where it's responsible for most cases of childhood diarrhea.
Yet the giardia parasite isn't just a problem in developing nations. Giardia infection (giardiasis) is one of the most common waterborne diseases in the United States. Though the parasites are often associated with backcountry streams and lakes, they also turn up in municipal water supplies, swimming pools, whirlpool spas and wells. Giardia infection, which is highly contagious, also can be transmitted through food and person-to-person contact.
Most cases of giardia infection clear up in two to six weeks without lasting effects. But some people have recurrent episodes for years or have intestinal problems long after the parasites are gone. Children who have a severe giardia infection may fail to grow normally or have learning difficulties later in life.
Although several drugs are generally effective against giardia parasites, not everyone responds to these medications. Drug resistance is also a growing problem, especially in people who need longer therapy or who are treated more than once. Prevention is your best defense against giardiasis.
Signs and symptoms
Some people with giardia infection particularly children never develop symptoms but still carry the parasite and can spread it to others. For those who do get sick, signs and symptoms usually appear a week to 10 days after exposure and may include:
- Watery, sometimes malodorous diarrhea that may alternate with soft, greasy stools
- Abdominal cramps and bloating
- Nausea
- Fatigue
- Weight loss as much as 10 to 15 pounds in adults
Causes
Giardia parasites have two forms: an active form that lives in the intestine of an infected animal or human and an inactive cyst form that can survive for months in the environment. When you ingest the cysts, their hard shells break down in your stomach, releasing the parasites. The parasites then attach to the wall of your small intestine, eventually reproducing themselves millions of times and damaging the intestinal wall. This interferes with your ability to absorb food, leading to diarrhea and weight loss.
In time, the parasites detach from the small intestine, transform back into cysts and are shed by the millions in your feces. They can survive in soil or water for long periods until they're ingested by another host. You're likely to pick up the parasites in one of three ways:
- In water. This is the main source of giardia infection. The parasites are found in lakes, ponds, rivers and streams worldwide, as well as in municipal water supplies, wells, cisterns, swimming pools, water parks and spas. Giardia parasites have even turned up in touch tanks in aquariums and museums. Ground and surface water can become contaminated from agricultural runoff and wastewater discharge. Because giardiasis affects beavers, muskrats, small rodents and a variety of birds, reptiles and fish, water can also become contaminated from animal feces. Children in diapers and people with diarrhea may accidentally contaminate pools and spas. You can become infected if you drink from streams or lakes that contain the parasites, drink contaminated tap water at home or abroad, or accidentally swallow water from a tainted pool or spa.
- In food. Giardia parasites can be transmitted through food either because food handlers with giardiasis dont wash their hands or because raw produce is irrigated or washed with contaminated water. Food is a less common source of infection than water is, especially in industrialized countries, but outbreaks have been traced to contaminated ice and infected food service workers.
- By direct contact. You can contract giardiasis if your hands become contaminated with fecal matter parents changing a child's diapers are especially at risk. So are child care workers and children in child care centers, where outbreaks are increasingly common. The giardia parasite also can spread through anal sex.
Children and adults who have giardia infection but no symptoms usually don't need treatment unless they're likely to spread the parasites. Many people who do have problems often get better on their own in a few weeks. When signs and symptoms are severe or the infection persists, doctors usually treat giardiasis with antibiotics such as metronidazole or tinidazole. The two drugs are equally effective, but tinidazole requires a shorter course of treatment. Both can cause side effects such as a metallic taste, nausea and vomiting, and you must avoid drinking alcohol while taking them. Pregnant women shouldn't use these drugs during the first trimester because they can lead to birth defects. Some doctors prefer not to treat women at all during pregnancy, or they may opt to use a less toxic though less effective drug.
Prevention
No drug can prevent giardia infection. And exposure to giardia parasites in food or municipal drinking water is unavoidable. Still, common-sense precautions can go a long way toward reducing the chances that you'll become infected or spread the infection to others.
For your own safety:
- Wash your hands. This is the simplest and best way to prevent most kinds of infection. Wash your hands after using the toilet or changing diapers and before eating or preparing food. Scrub your hands briskly with soap and warm water for at least 15 seconds. For children, this is about as long as it takes to say the ABCs or sing the "Happy birthday" song. Rinse thoroughly, allowing the water to run down your hands, and then dry your hands with a disposable paper towel. When soap and water aren't available, alcohol-based sanitizers containing at least 62 percent alcohol are an excellent alternative.
- Purify wilderness water. Avoid drinking untreated water from shallow wells, lakes, rivers, springs, ponds and streams unless you boil or filter it first.
- Leave no trace. If you're camping without access to a toilet, bury your waste and your pet's at least 6 inches deep and 200 feet from a water source. People with portable toilets should use sewage dump points.
- Keep your mouth closed. Try not to swallow water when swimming in pools, lakes or streams.
- Be wary of tap water. Each year in the United States, about 250 people in every 10,000 contract giardiasis from public drinking water. Water can become contaminated if standard treatments aren't effective or natural events such as flooding overwhelm treatment systems. If an outbreak of giardia infection occurs in your area, buy bottled water or boil or filter tap water before you use it.
- Use bottled water. When traveling to parts of the world where the water supply is likely to be unsafe, drink and brush your teeth with bottled water that you open yourself. Don't use ice, and avoid raw fruits and vegetables, even those you peel yourself.
- Practice safer sex. If you engage in anal sex, use a condom every time. Avoid oral-anal sex unless you're fully protected.
- Wash your hands. Scrub your hands with soap and warm water for at least 15 seconds after using the toilet and before handling food. If possible, have a friend or family member prepare meals until you're free of infection. Keep in mind that you can spread the parasites for several weeks after you stop having symptoms. Away from home, use an alcohol-based hand sanitizer containing at least 62 percent alcohol.
- Stay out of the water. Avoid all types of recreational water pools, hot tubs, whirlpool spas, lakes and streams for at least two weeks after your diarrhea has stopped. You can continue to spread the infection even if you no longer have symptoms.
- Be sex-safe. Avoid having anal or oral-anal sex until you're free from infection.
If you're not sure water is safe to drink, you can purify it using one of these methods:
- Heat or boil water to at least 158 F (70 C). Ten minutes should be enough to kill any parasites.
- Use a water filter. The Centers for Disease Control and Prevention recommends a filter having a pore size of 1 micron or smaller or one that has been rated by the National Science Foundation (NSF) as effective for cyst removal.
- Don't rely on chlorine or iodine water purification tablets they're not effective against giardia parasites.
Informations obtained from National Institute of Health.