Topic Name

A	B	C	D	E	F	G	H	I
J	K	L	M	N	O	P	Q	R
S	T	U	V	W	X	Y	Z	#

Disease Categories > Infectious Disease > Parasites

Font

Diarrhea, Parasitic Evaluation

Etiology of diarrhea may be infectious or non-infectious presenting with acute (<7 days) or chronic (>7 days) symptoms.

Acute diarrheal episodes (acute gastroenteritis)
- Frequently infectious
- May be food-borne, water-borne or outbreak associated
- Most commonly caused by viruses; occasionally bacteria
- Testing for gastrointestinal parasites generally not recommended for acute diarrheal episodes
  - Parasites are an infrequent or rare cause of acute diarrhea
    - 5-15% in preschool age children attending day care
    - 1-2% in adults
  - Giardia intestinalis is the most common, followed by Cryptosporidium spp or Entamoeba histolytica
  - If diarrhea persists (eg, >7 days) consider targeted testing
    - First G. intestinalis stool antigen (EIA) (first)
    - Cryptosporidium spp stool antigen (EIA)
    - E. histolytica stool antigen (EIA)
- Exceptions
  - Immunocompromised patients or recently returned travelers
    - History that suggests other etiologies such as Coccidia (eg, Cyclospora spp, Isospora belli), Microsporidia or other, less-common parasites
      - Strongyloides stercoralis – may require special test procedures (modified acid fast stain), Microsporidia stain, for ova and parasite examination) or serology
  - For patients with history of travel or residence in endemic area, immunocompromised patients or persistent symptoms and clinical concern for parasitic infection despite negative EIA, comprehensive stool ova and parasite examination with submission of ≥3 specimens over 10 days is recommended
Chronic diarrhea (>7 days, often longer)
- More commonly non-infectious
- May be parasitic
  - Giardia intestinalis is the most common, occasionally Cryptosporidium spp or Entamoeba histolytica
  - Targeted testing is preferred and most sensitive
    - First G. intestinalis stool antigen (EIA)
    - Cryptosporidium spp stool antigen (EIA)
    - E. histolytica stool antigen (EIA)
    - If diarrhea persists and above testing is negative
      - May consider
        
        Repeat stool antigen (EIA) as above
      - Refer to gastroenterologist for complete evaluation of infectious and non-infectious causes
      - If immunosuppressed, recently returned traveler, or individual from endemic area
        
        Ova and parasite examination with request for special stains
        
        Strongyloides stercoralis serology

Giardia intestinalis

Epidemiology

Incidence
- Annual incidence in adults estimated at 150-700 cases/100,000 population
- Increased frequency in children, homosexual males and institutional care facilities
- The most common cause of parasite-associated diarrhea in the U.S.
Transmission – water-borne, food-borne or person to person

Organism

Protozoal parasite that inhabits the small intestine

Clinical Presentation

Most infections are asymptomatic
Symptoms may include acute or chronic non-bloody diarrhea, nausea, abdominal discomfort, malabsorptive symptoms (eg, flatulence, greasy malodorous stools) lasting from weeks to months
Intermittent or recurrent symptoms are common

Diagnosis

Giardia stool antigen by EIA (preferred, most sensitive)

Treatment

May resolve/clear spontaneously in some cases
Recommended in symptomatic and asymptomatic disease to reduce transmission

Prevention

Cooking food adequately
Boiling or filtering potentially contaminated water

Cryptosporidium

Epidemiology

Incidence
- Estimated 20-100 cases/100,000 population per year
- Increased frequency in HIV infection, households of infected patients, child day-care centers, and travelers
Transmission – water-borne, sporadic or outbreak associated

Organism

Protozoan parasite frequently associated with water-borne outbreaks.

Clinical Presentation

Immunocompetent individuals – usually asymptomatic or mild self-limited gastroenteritis; symptoms may include non-bloody diarrhea, nausea, vomiting, abdominal pain, low-grade fever and malaise lasting from days to occasionally more than a month
Immunocompromised individuals – chronic more often severe diarrhea, dehydration, weight-loss

Diagnosis

Cryptosporidium spp stool antigen (EIA or DFA) preferred, most sensitive Microscopic examination of stool requires special stains (eg, modified acid fast); less sensitive than stool EIA

Treatment

Generally not necessary in immunocompetent individuals
Severe disease, immunocompromised host – supportive therapy, no single effective therapy, nitaxozanide may be considered

Entamoeba spp

Epidemiology

Prevalence
- Estimated 4% prevalence of E. histolytica in industrialized nations
- Increased frequency in homosexual men, immigrants, institutional care settings, travelers, HIV patients
Transmission – water-borne, food-borne, or person to person

Organism

Enteric protozoa among which only Entamoeba histolytica is considered pathogenic.

Clinical Presentation

Most individuals are asymptomatically colonized (~90%)
Disease may be intestinal or extraintestinal
Intestinal disease may be asymptomatic or symptomatic, fulminant or chronic, with abdominal pain, tenderness, tenesmus, and bloody diarrhea
Extraintestinal disease may include liver, brain and lung abscesses

Diagnosis

For intestinal disease – Entamoeba histolytica stool antigen (EIA )
For extraintestinal disease (eg, liver abscess) – serologic testing preferred (Entamoeba histolytica antibody, IgG); stool antigen or ova and parasite exam are generally negative

Treatment

Generally recommended for symptomatic and asymptomatic individuals to prevent transmission

Prevention

Boiling or filtering contaminated water

Isospora belli

Epidemiology

Incidence
- Unknown
- Increased frequency in HIV, institutional care settings, day-care centers
Transmission – water-borne

Organism

Coccidian parasite related to Cryptosporidium spp

Clinical Presentation

Immunocompetent individuals – acute self-limited watery or malodorous diarrhea similar to Giardia or Cryptosporidium infection
Immunocompromised individuals – chronic diarrhea, which is occasionally severe, dehydration, weight-loss

Diagnosis

Microscopic examination of stool including special stain (eg, modified acid fast)

Treatment

May be indicated in immunocompromised hosts

Microsporidia

Epidemiology

Incidence
- Unknown
- Increased frequency in AIDS patients with chronic diarrhea
Transmission – water-borne
Occurrence – immunocompromised persons (especially those with HIV infection)

Organism

Obligate intracellular parasites predominately affecting immunocompromised hosts
Includes Enterocytozoon bieneusi, Encephalitozoon intestinalis, Pleistophora, Septata, Vittaforma spp

Clinical Presentation

Immunocompetent individuals – rare cause of acute self-limited diarrhea
Immunocompromised individuals – chronic diarrhea, dehydration, anorexia, weight loss

Diagnosis

Microscopic examination of the stool
- Requires special stain (microsporidia stain)
May require testing of multiple specimens

Treatment

May be indicated in immunocompromised patients

Strongyloides stercoralis

Epidemiology

Incidence
- Unknown in U.S.
- Increased frequency in endemic areas, institutional care settings, day-care centers, homosexual males
Transmission – infectious filariform larvae in soil or environment enters the body by penetrating the skin

Clinical Presentation

Cutaneous
- Serpiginous urticarial rash due to larval migrations, “Larva currens"
- Cutaneous larva migrans may also be observed with infections by other nematodes such as Ancylostoma spp, Uncinaria stenocephala and Bunostomum phlebotomum
Pulmonary
- Symptoms are associated with primary larval migration, increased in hyperinfection with larvae in pulmonary secretions
Intestinal
- Generally asymptomatic, chronic infection; occasionally intermittent diarrhea, abdominal pain; rarely, obstruction, ulcers, enterocolitis, malabsorption, hemorrhage, right upper quadrant pain, sepsis
Hyperinfection
- Frequent in immunocompromised patients
- Occurs when host immunity no longer prevents larval reentry via intestinal wall
- Disseminated infection with large numbers of larvae found in every tissue of the body
- Life threatening

Diagnosis

Serology is most sensitive
Ova and parasite exam may miss organisms in light infections requiring examination of multiple specimens

Treatment

Indicated in all cases

Indications for Ordering

Tests generally appear in the order most useful for common clinical situations
Click on number for test-specific information in the ARUP Laboratory Test Directory

Test Name and Number	Recommended Use	Limitations	Follow Up
Giardia Antigen by EIA 0060048 Method: Enzyme Immunoassay	Diagnose Giardia as etiology of diarrheal disease Most sensitive method for detection of Giardia lamblia	Will not detect parasites other than G. lamblia May require testing of multiple specimens
Giardia lamblia Antibody by IFA 0099439 Method: Immunofluorescence Assay	Diagnose Giardia as etiology of diarrheal disease after 1-2 weeks of chronic disease Presence of IgG, IgA and IgM are detected in this test	Insensitive relative to stool EIA
Cryptosporidium Antigen by EIA 0060045 Method: Enzyme Immunoassay	Diagnose Cryptosporidium as etiology of diarrheal disease Most sensitive test for detection of Cryptosporidium spp	Will not detect parasites other than Cryptosporidium spp May require testing of multiple specimens
Entamoeba histolytica Antigen, EIA 0058001 Method: Enzyme Immunoassay	Diagnose Entamoeba as etiology of diarrheal disease Order only for patients at risk for infection (foreign travel) Specific and sensitive test for detection of intestinal E. histolytica	Rarely positive in extraintestinal disease Will not detect parasites other than E. histolytica May require testing of multiple specimens
Entamoeba histolytica (amebiasis), Antibody, IgG 0050070 Method: Enzyme-Linked Immunosorbent Assay	Confirm past infection Diagnose invasive extraintestinal disease	Preferred test for extraintestinal disease (eg liver abscess)
Parasitology Stain by Modified Acid-Fast 0060046 Method: Concentration/Modified Acid-Fast Stain	Detect Cryptosporidium, Cyclospora and Isospora	Not intended for detection of other stool parasites Less sensitive than EIA for Cryptosporidium spp
Microsporidia Stain 0060050 Method: Modified Trichrome Stain	Detect Microsporidia	Not intended for detection of other stool parasites
Ova & Parasite Exam, Fecal (Immunocompromised or Travel History) 0060240 Method: Concentration Technique/Trichrome Stain/Microscopic Evaluation	Diagnose most parasites such as Taenia spp Strongyloides, Giardia, Entamoeba as etiology of diarrheal disease in patient with immunocompromised condition, pertinent travel and exposure history, or high pre-test probability for parasitic infection Recommend collection of 3 separate stool specimens within 10 days	Insensitive relative to stool EIA for most common pathogen Requires examination of 2-3 stool samples to improve sensitivity Does not include a test to specifically detect Cryptosporidium, Cyclospora, Isospora and Microsporidium
Strongyloides Antibody, IgG by ELISA, Serum 0099564 Method: Enzyme-Linked Immunosorbent Assay	Confirm clinical suspicion of Strongyloides infection in patient	Most sensitive test in chronic infections	Antibody cross-reactions in patients with filariasis may occur

Additional Information

For patients with history of travel or residence in endemic area, immunocompromised patients or persistent symptoms and clinical concern for parasitic infection despite negative EIA, comprehensive stool ova & parasite examination with submission of ≥3 specimens over 10 days is recommended including request for special stains.

General References

Caccio SM, Thompson RC, McLauchlin J, Smith HV. Unravelling Cryptosporidium and Giardia epidemiology. Trends Parasitol. 2005;21(9):430-437. (Link to PubMed)

Concha R, Harrington W Jr, Rogers AI. Intestinal strongyloidiasis: recognition, management, and determinants of outcome. J Clin Gastroenterol. 2005;39(3):203-211. (Link to PubMed)

Forrest G. Gastrointestinal infections in immunocompromised hosts. Curr Opin Gastroenterol. 2004;20(1):16-21. (Link to PubMed)

Goodgame R. A Bayesian approach to acute infectious diarrhea in adults. Gastroenterol Clin North Am. 2006;35(2):249-273. (Link to PubMed)

Guerrant RL, Van Gilder T, Steiner TS, Thielman NM, Slutsker L, Tauxe RV, Hennessy T, Griffin PM, DuPont H, Sack RB, Tarr P, Neill M, Nachamkin I, Reller LB, Osterholm MT, Bennish ML, Pickering LK. Practice guidelines for the management of infectious diarrhea. Clin Infect Dis. 2001;32(3):331-351. (Link to PubMed)

Huang DB, White AC. An updated review on Cryptosporidium and Giardia. Gastroenterol Clin North Am. 2006;35(2):291-314, viii. (Link to PubMed)

Keiser PB, Nutman TB. Strongyloides stercoralis in the Immunocompromised Population. Clin Microbiol Rev. 2004;17(1):208-217. (Link to PubMed)

Kosek M, Alcantara C, Lima AA, Guerrant RL. Cryptosporidiosis: an update. Lancet Infect Dis. 2001;1(4):262-269. (Link to PubMed)

Mathis A, Weber R, Deplazes P. Zoonotic potential of the microsporidia. Clin Microbiol Rev. 2005;18(3):423-445. (Link to PubMed)

Segarra-Newnham M. Manifestations, diagnosis, and treatment of Strongyloides stercoralis infection. Ann Pharmacother. 2007;41(12):1992-2001. (Link to PubMed)

Siddiqui AA, Berk SL. Diagnosis of Strongyloides stercoralis infection. Clin Infect Dis. 2001;33(7):1040-1047. (Link to PubMed)

Thielman NM, Guerrant RL. Clinical practice. Acute infectious diarrhea. N Engl J Med. 2004;350(1):38-47. (Link to PubMed)

Thom K, Forrest G. Gastrointestinal infections in immunocompromised hosts. Curr Opin Gastroenterol. 2006;22(1):18-23. (Link to PubMed)

Viney ME, Lok JB. Strongyloides spp. WormBook. 2007;1-15. (Link to PubMed)

Zaha O, Hirata T, Kinjo F, Saito A. Strongyloidiasis--progress in diagnosis and treatment. Intern Med. 2000;39(9):695-700. (Link to PubMed)

Reviewed by

Litwin, Christine, M.D. Medical Director, Immunology at ARUP Laboratories; Professor, Clinical Pathology, University of Utah

Petti, Cathy A., M.D. Medical Director, Infectious Diseases at ARUP Laboratories; Assistant Professor, Pathology and Medicine, University of Utah

Comprehensive Review: May 2008
Last Update: July 2008