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) [1] [2] [3]
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 (non-typhi)
- Escherichia coli
- E. coli 0157:H7
- Yersinia enterocolitica
- Vibrio cholerae
- Clostridium difficile
- Parasitic
- Toxin
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)[4]
- Norovirus (often has prominent vomiting)
- Campylobacter
- Non-typhoidal Salmonella
- Enteroaggregative E. coli (EAEC)
- Enterotoxigenic Bacteroides fragilis
Traveler's Diarrhea
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 [5]
- Suspect protozoan illness in patients with diarrhea > 2 weeks
Management
Treatment is not always successful [6]
- Metronidazole
- Adult: 250mg TID x 7-10 days
- Children: 5mg/kg TID x 7 days (max dose 500mg TID)
- Albendazole[7]
- 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 [8]
References
- ↑ Marx, John A., Robert S. Hockberger, Ron M. Walls, James Adams, and Peter Rosen. "Chapter 94 -- Gastroenteritis." Rosen's Emergency Medicine Concepts and Clinical Practice. Philadelphia: Mosby/Elsevier, 2010. Print.
- ↑ Tintinalli, Judith E., and J. Stephan. Stapczynski. "Chapter 156 -- World Traveler." Tintinalli's Emergency Medicine: A Comprehensive Study Guide. New York: McGraw-Hill, 2011. Print.
- ↑ Tintinalli, Judith E., and J. Stephan. Stapczynski. "Chapter 154 -- Foodborne and Waterborne Diseases." Tintinalli's Emergency Medicine: A Comprehensive Study Guide. New York: McGraw-Hill, 2011. Print.
- ↑ Marx et al. “Cholera and Gastroenteritis caused by Noncholera Vibrio Species”. Rosen’s Emergency Medicine 8th edition vol 1 pg 1245-1246.
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/22632642
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/20086650
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/23235648
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/23192407