Giardia

Giardia suspected cause of diarrhea in humans.

Illness & Symptoms

Giardiasis is the most frequently diagnosed intestinal parasitic disease in the United States and among travelers with chronic diarrhea. Signs and symptoms may vary and can last for 1 to 2 weeks or longer. In some cases, people infected with Giardia have no symptoms.

Giardia life cycle

Acute symptoms include:

• Diarrhea
• Gas
• Greasy stools that tend to float
• Stomach or abdominal cramps
• Upset stomach or nausea/vomiting
• Dehydration (loss of fluids)

Other, less common symptoms include itchy skin, hives, and swelling of the eye and joints. Sometimes, the symptoms of giardiasis might seem to resolve, only to come back again after several days or weeks. Giardiasis can cause weight loss and failure to absorb fat, lactose, vitamin A and vitamin B12.

Giardia Trophozoite

Children

In children, severe giardiasis might delay physical and mental growth, slow development, and cause malnutrition

• Giardia is a microscopic parasite that causes the diarrheal illness known as giardiasis.
• Giardia is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it tolerant to chlorine disinfection.

Giardia Cyst

Transmission

• While the parasite can be spread in different ways, water (drinking water and recreational water) is the most common mode of transmission.
• Giardiasis is a diarrheal illness caused by the parasite Giardia intestinalis (also known as Giardia lamblia or Giardia duodenalis).
• A parasite is an organism that feeds off of another to survive.
• Giardiasis is a global disease. It infects nearly 2% of adults and 6% to 8% of children in developed countries worldwide.
• Nearly 33% of people in developing countries have had giardiasis.
• In the United States, Giardia infection is the most common intestinal parasitic disease affecting humans.

Giardia intestinalis

Risk factors

• Travelers to countries where giardiasis is common
• People in childcare settings
• Those who are in close contact with someone who has the disease
• People who swallow contaminated drinking water
• Backpackers or campers who drink untreated water from lakes or rivers
• People who have contact with animals who have the disease
• Men who have sex with men

Giardia trophozoites Giemsa

Diagnosis & Detection

• Giardia trophozoites and cysts under a microscope.
• Giardia trophozoites and cysts. Credit: Waterborne Disease Prevention Branch, CDC

Treatment

• Giardia trophozoites under a scanning electron microscope.
• Giardia trophozoites under scanning electron microscope. Credit: Waterborne Disease Prevention Branch, CDC
• Several drugs can be used to treat Giardia infection. Effective treatments include metronidazole, tinidazole, and nitazoxanide. Alternatives to these medications include paromomycin, quinacrine, and furazolidone. Some of these drugs may not be routinely available in the United States.

Different factors may shape how effective a drug regimen will be, including medical history, nutritional status, and condition of the immune system. Therefore, it is important to discuss treatment options with a healthcare provider.

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