Giardiasis

Infectious Agent

The anaerobic protozoan parasite Giardia intestinalis (formerly known as G. lamblia or G. duodenalis ).

Transmission

Giardia is transmitted via the fecal-oral route. Its low infectious dose, protracted communicability, and moderate chlorine tolerance make Giardia ideally suited for transmission through drinking and recreational water. Transmission also occurs through person-to-person contact, such as caring for an infected person, through sexual contact, through eating food contaminated by infected food handlers or by contaminated water used for irrigation or washing food, and by contact with fecally contaminated surfaces.

Epidemiology

Giardia is endemic worldwide. Giardia -related acute diarrhea was a top 10 diagnosis in ill US travelers returning from the Caribbean, Middle East, Eastern Europe, Central America, South America, North Africa, sub-Saharan Africa, and South-Central Asia. The risk of infection increases with duration of travel. Backpackers or campers who drink untreated water from lakes or rivers are also more likely to be infected. Giardia is commonly identified in routine screening of refugees and internationally adopted children, although many are asymptomatic.

Clinical Presentation

Many infected are asymptomatic, though if symptoms develop, they typically develop 1–2 weeks after infection and generally resolve within 2–4 weeks. Symptoms include diarrhea (often with foul-smelling, greasy stools), abdominal cramps, bloating, flatulence, fatigue, anorexia, and nausea. Usually, a patient presents with the gradual onset of 2–5 loose stools per day and gradually increasing fatigue. Sometimes upper gastrointestinal symptoms are more prominent. Weight loss may occur over time. Fever and vomiting are uncommon. Reactive arthritis, irritable bowel syndrome, and other chronic symptoms sometimes occur after infection with Giardia (see Chapter 5, Persistent Travelers’ Diarrhea).

Diagnosis

Giardia cysts or trophozoites are not consistently seen in the stools of infected patients. Diagnostic yield can be increased by examining up to 3 stool samples over several days. Direct fluorescent antibody testing is extremely sensitive and specific. Rapid immunochromatographic cartridge assays also are available but should not take the place of routine ova and parasite examination. Only molecular testing (such as PCR) can be used to identify the subtypes of Giardia . Retesting is only recommended if symptoms persist after treatment. Giardiasis is a nationally notifiable disease.

Treatment

Effective treatments include metronidazole, tinidazole, and nitazoxanide. An alternative is paromomycin. Because making a definitive diagnosis is difficult, empiric treatment can be used in patients with the appropriate history and typical symptoms.

Prevention

Food and water precautions (see Chapter 2, Food & Water Precautions and Water Disinfection for Travelers) and hand hygiene.

CDC website: www.cdc.gov/parasites/giardia

Bibliography

  1. Abramowicz M, editor. Drugs for Parasitic Infections. New Rochelle (NY): The Medical Letter, Inc.; 2013.
  2. Adam EA, Yoder JS, Gould LH, Hlavsa MC, Gargano JW. Giardiasis outbreaks in the United States, 1971–2011. Epidemiol Infect. 2016 Oct;144(13):2790–801.  [PMID:26750152]
  3. Cantey PT, Roy S, Lee B, Cronquist A, Smith K, Liang J, et al. Study of nonoutbreak giardiasis: novel findings and implications for research. Am J Med. 2011 Dec;124(12):1175 e1–8.
  4. Escobedo AA, Cimerman S. Giardiasis: a pharmacotherapy review. Expert Opin Pharmacother. 2007 Aug;8(12):1885–902.  [PMID:17696791]
  5. Hagmann SH, Han PV, Stauffer WM, Miller AO, Connor BA, Hale DC, et al. Travel-associated disease among US residents visiting US GeoSentinel clinics after return from international travel. Fam Pract. 2014 Dec;31(6):678–87.  [PMID:25261506]
  6. Harvey K, Esposito DH, Han P, Kozarsky P, Freedman DO, Plier DA, et al. Surveillance for travel-related disease—GeoSentinel Surveillance System, United States, 1997–2011. MMWR Surveill Summ. 2013 Jul 19;62:1–23.
  7. Johnston SP, Ballard MM, Beach MJ, Causer L, Wilkins PP. Evaluation of three commercial assays for detection of giardia and cryptosporidium organisms in fecal specimens. J Clin Microbiol. 2003 Feb;41(2):623–6.  [PMID:12574257]
  8. Ross AG, Cripps AW. Enteropathogens and chronic illness in returning travelers. N Engl J Med. 2013 Aug 22;369(8):784.
  9. Staat MA, Rice M, Donauer S, Mukkada S, Holloway M, Cassedy A, et al. Intestinal parasite screening in internationally adopted children: importance of multiple stool specimens. Pediatrics. 2011 Sep;128(3):e613–22.  [PMID:21824880]
  10. Swaminathan A, Torresi J, Schlagenhauf P, Thursky K, Wilder-Smith A, Connor BA, et al. A global study of pathogens and host risk factors associated with infectious gastrointestinal disease in returned international travellers. J Infect. 2009 Jul;59(1):19–27.  [PMID:19552961]

Authors

Kathleen E. Fullerton, Jonathan S. Yoder