GI IMPACT Study

The Diarrhea Study

Giardia - Information for Clinicians

Type of infection

Giardia intestinalis (also known as Giardia lamblia) is a flagellated protozoal parasite. Both trophozoite and cyst forms are excreted.

Source of infection

  1. Giardia infects the intestines of humans and many types of animals (cats, dogs, livestock, deer, muskrats, beavers, voles, guinea pigs, and ferrets).
  2. The infectious dose is quite low (~10 cysts).
  3. Infection is associated with child care centers, travel to developing countries, swallowing untreated or contaminated water from lakes, ponds and rivers, and direct contact with animals.
  4. Humans can acquire Giardia from dogs and cats but according to the CDC this risk is small.

Usual symptoms

  1. The incubation period is 7-14 days.
  2. Symptoms of acute infection include flatulence, bloating, diarrhea, foul-smelling and fatty stools, nausea, and abdominal cramps.
  3. Weight loss is common and can be profound.
  4. Acquired lactose intolerance develops in 20-40% and may be slow to resolve.
  5. Symptoms of chronic infection include loose stools without overt diarrhea, steatorrhea, malaise, fatigue, malabsorption, abdominal cramping, flatulence, and burping.

Treatment

  1. Dehydration and electrolyte abnormalities should be treated.
  2. Most symptomatic patients should be treated with antimicrobial agents.
  3. Tinidazole (50 mg/kg as a single dose up to 2000 mg for children >3), metronidazole (15 mg/kg/day div tid up to 250 mg per dose for 5-7 days), or nitazoxanide are the drugs of choice. Cure rates are highest for tinidazole and it can be given as a single dose.
  4. Alternative agents with activity include albendazole, mebendazole, or paromomycin.
  5. Longer durations of therapy should be considered in immunocompromised children.
  6. Symptoms may take 5-7 days to resolve, parasites are cleared from the stool in 3-5 days.
  7. Recurrent symptoms may be due to lactose intolerance, re-infection, or treatment failure.

Complications

  1. Malabsorption, growth retardation, hypoalbuminemia, vitamin B12 deficiency and folate deficiency, anemia.

Comments

  1. Children with diarrhea due to Giardia should be excluded from child care until symptoms resolve.
  2. Local health departments should be notified of Giardia in child care center attendees.
  3. Campers and hikers should use filtration, boiling, or chemical disinfection for drinking water.
  4. People with diarrhea due to Giardia should not use recreational water venues (swimming pools, water parks, etc.) for 2 weeks after symptoms resolve.

Resources

  1. CDC Handout
  2. Red Book