What Is Giardiasis?

Giardiasis is a common intestinal infection caused by a microscopic parasite called Giardia lamblia (also known as Giardia intestinalis). It spreads through contaminated water, food, or surfaces and can cause diarrhea, stomach cramps, and other digestive issues. It affects both children and adults and is especially common in areas with poor sanitation.

What Causes Giardiasis?

Giardiasis is caused by swallowing Giardia cysts, which are found in:

• Contaminated drinking water (often from lakes, rivers, or poorly treated tap water)
• Unwashed fruits or vegetables
• Surfaces or objects contaminated with infected feces
• Contact with infected individuals or animals
• Poor hygiene, especially in childcare settings

Once ingested, the parasite attaches to the lining of the small intestine and disrupts nutrient absorption, leading to symptoms.

Symptoms of Giardiasis

Symptoms usually appear 1 to 3 weeks after infection and can last for several weeks. Common signs include:

• Watery or greasy diarrhea
• Abdominal cramps and bloating
• Nausea
• Gas and flatulence
• Dehydration
• Fatigue
• Weight loss
• Occasional vomiting
• Foul-smelling stools

Some people may be infected and have no symptoms but can still spread the parasite to others.

How Is Giardiasis Diagnosed?

Doctors diagnose giardiasis using one or more of the following:

• Stool sample test – to detect the parasite or its cysts
• Antigen tests – to check for Giardia proteins in stool
• Multiple stool samples – may be needed because the parasite is shed intermittently
• Endoscopy (rare) – if other tests are inconclusive and symptoms persist

Treatment Options for Giardiasis

Giardiasis is treatable with prescription medications. The most common include:

• Metronidazole – often prescribed for 5–7 days
• Tinidazole – a single-dose treatment
• Nitazoxanide – especially used in children

Additional supportive care may include:

• Drinking plenty of fluids to prevent dehydration
• Oral rehydration salts (ORS) for severe diarrhea
• Avoiding dairy products temporarily if lactose intolerance develops after infection

Can Giardiasis Be Prevented?

Yes, prevention involves good hygiene and safe practices:

• Drink only clean, treated, or bottled water
• Avoid swallowing water from lakes, rivers, or pools
• Wash fruits and vegetables thoroughly before eating
• Practice proper handwashing after using the bathroom or changing diapers
• Use safe water sources when traveling
• Boil or filter water when in doubt

Who Is at Risk for Giardiasis?

Anyone can get giardiasis, but certain groups are at higher risk:

• Travelers to areas with poor sanitation
• Campers and hikers who drink untreated water
• Children in daycare centers
• People with weakened immune systems
• Those in close contact with infected individuals

Complications of Giardiasis

If untreated or in people with weakened immune systems, giardiasis can cause:

• Chronic diarrhea
• Weight loss and malnutrition
• Dehydration
• Lactose intolerance
• Failure to thrive in children

Living with Giardiasis

Most people recover fully with proper treatment. To avoid reinfection or spreading it to others:

• Complete the full course of medication
• Wash hands frequently
• Avoid preparing food for others while infected
• Clean and disinfect surfaces, especially in bathrooms

When to See a Doctor

Seek medical attention if:

• Diarrhea lasts more than a few days
• There’s blood in the stool
• You develop signs of dehydration (dry mouth, dizziness, reduced urination)
• You experience severe abdominal pain or weight loss