Giardia lamblia

Background

• Flagellated protozoan
• Most common cause of parasitic diarrhea worldwide
• Transmitted by water contaminated with feces (human, beaver, muskrat, dogs, raccoons, etc)
• Common among campers and is also known as “backpacker’s diarrhea”
• Common in travelers to former Soviet Union, Caribbean, Latin America, India, Africa
• Infection rate is twice as high during summer months
• Also may be transmitted by contaminated food or close physical contact (sexual activity, daycare centers, etc)
• Patients with decreased gastric acidity, immunoglobulin deficiency, or immunocompromise are more susceptible
• Other names: “beaver fever”, “the Trotskys” (common in travelers to Leningrad)

Pathophysiology

• Trophozoites infect duodenum, jejunum, and ileum where they form cysts
• Cysts are passed in feces; viable for long periods of time
• A single diarrheal stool may contain hundreds of millions of cysts or parasites

Clinical Features

• Often asymptomatic
• Most common symptoms include:
  • Abdominal distension
  • Colicky abdominal pain
  • Flatulence
  • Diarrhea (pale, loose, floating, foul odor)
  • Borborygmi
• No blood or mucus in stool
• Sudden onset after incubation period of 1-3 weeks
• Symptoms usually resolve in 7-10 days
• 85% of the time infection resolves spontaneously within 6 weeks
• May cause chronic malabsorption-like illness, especially in those with immunoglobulin deficiency
• Chronic infections cause weight loss, anemia, lactose intolerance

Differential Diagnosis

Acute diarrhea

Infectious

• Viral (e.g. rotavirus)
• Bacterial
  • Campylobacter
  • Shigella
  • Salmonella (nontyphi)
  • Escherichia coli
    • E. coli 0157:H7
  • Yersinia enterocolitica
  • Vibrio cholerae
  • Clostridium difficile
• Parasitic
  • Giardia lamblia
  • Cryptosporidium
  • Entamoeba histolytica
  • Cyclospora
• Toxin
  • Staphylococcus aureus
  • Bacillus cereus

Noninfectious

• GI Bleed
• Appendicitis
• Mesenteric Ischemia
• Diverticulitis
• Adrenal Crisis
• Thyroid Storm
• Toxicologic exposures
• Antibiotic or drug-associated

Watery Diarrhea

• Enterotoxigenic E. coli (most common cause of watery diarrhea)
• Norovirus (often has prominent vomiting)
• Campylobacter
• Non-typhoidal Salmonella
• Enteroaggregative E. coli (EAEC)
• Enterotoxigenic Bacteroides fragilis

Traveler's Diarrhea

• Giardia lamblia
• Cryptosporidiosis
• Entamoeba histolytica
• Cyclospora

Evaluation

• Normal WBC, no eosinophilia
• Stool O&P
  • Motile trophozoites or cysts
  • Able to diagnose infection readily in acute illness
  • More difficult to diagnose in chronic or asymptomatic infection
• Antigen testing with ELISA, DFA, etc starting to replace microscopic examination with similar cost
• Suspect protozoan illness in patients with diarrhea > 2 weeks

Management

Treatment is not always successful

• Metronidazole
  • Adult: 250mg TID x 7-10 days
  • Children: 5mg/kg TID x 7 days (max dose 500mg TID)
• Albendazole
  • 400mg PO daily x 5-10 days
• Tinidazole
  • Adult: 2 grams PO x 1 dose
  • Children: 50mg/kg PO x 1 dose
• Quinacrine
  • > 8 years old: 100mg TID x 7 days
  • < 8 years old: 2mg/kg TID x 7 days
• Nitazoxanide
  • > 12 years old: 500mg BID x 3 days
  • 4-11 years old: 200mg BID x 3 days
  • 12-47 months old: 100mg BID x 3 days

Public Health Measures

• Strict adherence to handwashing (toileting, diaper changes, playing with pets, etc)
• Treat household members and/or sexual contacts if infected
• Treat asymptomatic infections in those at high-risk of transmitting to others (children in daycare, food handlers, etc) or those at risk of chronic symptoms
• Reinfection universal within 3 months in heavily infected endemic areas; treatment is not cost-effective in this setting

Disposition

• Disease is usually self-limited
• Admit those with systemic symptoms, severe dehydration, inability to tolerate PO fluids, or those with significant co-morbidities
• Supplementation with zinc and probiotics reduce severity/duration of diarrhea

References

Authors

Ross Donaldson