Overview
Giardia infection is an intestinal infection marked by stomach cramps, bloating, nausea and bouts of watery diarrhea. Giardia infection is caused by a microscopic parasite that is found worldwide, especially in areas with poor sanitation and unsafe water.
Giardia infection (giardiasis) is one of the most common causes of waterborne disease in the United States. The parasites are found in backcountry streams and lakes but also in public water supplies, swimming pools, whirlpool spas and wells. Giardia infection can be spread through food and person-to-person contact.
Giardia infections usually clear up within a few weeks. But you may have intestinal problems long after the parasites are gone. Several drugs are generally effective against giardia parasites, but not everyone responds to them. Prevention is your best defense.
Some people with giardia infection never develop signs or symptoms, but they still carry the parasite and can spread it to others through their stool. For those who do get sick, signs and symptoms usually appear one to three weeks after exposure and may include:
- Watery, sometimes foul-smelling diarrhea that may alternate with soft, greasy stools
- Fatigue
- Stomach cramps and bloating
- Gas
- Nausea
- Weight loss
Signs and symptoms of giardia infection may last two to six weeks, but in some people they last longer or recur.
When to see a doctor
Call your doctor if you have loose stools, stomach cramping and bloating, and nausea lasting more than a week, or if you become dehydrated. Be sure to tell your doctor if you're at risk of giardia infection — that is, you have a child in child care, you've recently traveled to an area where the infection is common, or you've swallowed water from a lake or stream.
Request an appointment
From Mayo Clinic to your inbox
Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.
To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.
Causes
Giardia parasites live in the intestines of people and animals. Before the microscopic parasites are passed in stool, they become encased within hard shells called cysts, which allows them to survive outside the intestines for months. Once inside a host, the cysts dissolve and the parasites are released.
Infection occurs when you accidentally swallow the parasite cysts. This can occur by swallowing unsafe water, by eating infected food or through person-to-person contact.
Swallowing contaminated water
The most common way to become infected with giardia is after swallowing unsafe (contaminated) water. Giardia parasites are found in lakes, ponds, rivers and streams worldwide, as well as in public water supplies, wells, cisterns, swimming pools, water parks and spas. Ground and surface water can become infected with giardia from agricultural runoff, wastewater discharge or animal feces. Children in diapers and people with diarrhea may accidentally contaminate pools and spas.
Eating contaminated food
Giardia parasites can be spread through food — either because food handlers with giardia infection don't wash their hands thoroughly or because raw produce is irrigated or washed with unsafe (contaminated) water. Because cooking food kills giardia, food is a less common source of infection than water is, especially in industrialized countries.
Person-to-person contact
You can get infected with giardia if your hands become dirty with feces — 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 can also spread through anal sex.
Risk factors
The giardia parasite is a very common intestinal parasite. Although anyone can pick up giardia parasites, some people are especially at risk:
- Children. Giardia infection is far more common in children than it is in adults. Children are more likely to come in contact with feces, especially if they wear diapers, are toilet training or spend time in a child care center. People who live or work with small children also are at higher risk of developing giardia infection.
- People without access to safe drinking water. Giardia infection is rampant wherever sanitation is inadequate or water isn't safe to drink. You're at risk if you travel to places where giardia infection is common, especially if you aren't careful about what you eat and drink. The risk is greatest in rural or wilderness areas.
- People who have anal sex. People who have anal sex or oral-anal sex without using a condom or other protection are at increased risk of giardia infection, as well as sexually transmitted infections.
Complications
Giardia infection is almost never fatal in industrialized countries. But it can cause lingering symptoms and serious complications, especially in infants and children. The most common complications include:
- Dehydration. Often a result of severe diarrhea, dehydration occurs when the body doesn't have enough water to carry out its normal functions.
- Failure to thrive. Chronic diarrhea from giardia infection can lead to malnutrition and harm children's physical and mental development.
- Lactose intolerance. Many people with giardia infection develop lactose intolerance — the inability to properly digest milk sugar. The problem may persist long after the infection has cleared.
Prevention
No drug or vaccine can prevent giardia infection. But commonsense precautions can go a long way toward reducing the chances that you'll become infected or spread the infection to others.
- Wash your hands. This is the simplest and best way to prevent most kinds of infection. Wash your hands with soap and water for at least 20 seconds after using the toilet or changing diapers, and before eating or preparing food. When soap and water aren't available, you can use alcohol-based sanitizers. However, alcohol-based sanitizers aren't effective in destroying the cyst form of giardia that survives in the environment.
- Purify wilderness water. Avoid drinking untreated water from shallow wells, lakes, rivers, springs, ponds and streams unless you filter it or boil it for at least 10 minutes at 158 F (70 C) first.
- Wash produce. Wash any raw fruits and vegetables with safe, uncontaminated water. Peel the fruit before eating it. Avoid eating raw fruits or vegetables if traveling in countries where they may have contact with unsafe water.
- Keep your mouth closed. Try not to swallow water when swimming in pools, lakes or streams.
- 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.
- Practice safer sex. If you engage in anal sex, use a condom every time. Avoid oral-anal sex unless you're fully protected.
As an expert in the field of infectious diseases, particularly gastrointestinal infections, I can confidently provide comprehensive insights into the concepts presented in the article on Giardia infection.
Giardia Infection Overview: Giardia infection, also known as giardiasis, is an intestinal infection caused by microscopic parasites. The infection is characterized by symptoms such as stomach cramps, bloating, nausea, and watery diarrhea. The causative agent, Giardia parasites, is a worldwide concern, particularly in areas with poor sanitation and unsafe water.
Distribution and Common Sources: Giardia parasites can be found in various environments, including backcountry streams, lakes, public water supplies, swimming pools, whirlpool spas, and wells. The infection can be waterborne and is prevalent in both developed and developing countries. Poor sanitation, contaminated water sources, and infected food are major contributors to the spread of Giardia.
Symptoms of Giardia Infection: Symptoms of giardiasis may include watery and foul-smelling diarrhea, fatigue, stomach cramps, bloating, gas, nausea, and weight loss. The onset of symptoms typically occurs one to three weeks after exposure. Some individuals may remain asymptomatic carriers, spreading the infection through their stool.
Causes and Transmission: Giardia parasites reside in the intestines of humans and animals, with cysts allowing them to survive outside the body for months. Infection occurs when individuals accidentally swallow the parasite cysts. Common modes of transmission include swallowing contaminated water from lakes or streams, consuming infected food, and person-to-person contact, especially through dirty hands.
Risk Factors: Certain groups are at higher risk of giardia infection, including children, individuals without access to safe drinking water, and those engaging in anal sex or oral-anal sex without protection. Children, in particular, are more susceptible due to factors like diaper use and time spent in childcare settings.
Complications of Giardia Infection: While giardia infection is rarely fatal in industrialized countries, it can lead to complications such as dehydration, failure to thrive in infants and children, and the development of lactose intolerance. Chronic diarrhea from giardiasis can result in malnutrition and hinder physical and mental development in children.
Prevention Strategies: Preventing giardia infection involves commonsense precautions. Key preventive measures include thorough handwashing, purifying wilderness water before consumption, washing raw fruits and vegetables, avoiding swallowing water during swimming, using bottled water in areas with unsafe water supply, and practicing safer sex, particularly for those engaging in anal activities.
In conclusion, giardia infection is a significant public health concern with various preventive measures and treatment options. Understanding the causes, symptoms, and risk factors is crucial for individuals to take proactive steps in safeguarding their health.
