Diarrhea, Parasitic Evaluation

Algorithm(s)

PDF algorithm(s) available at www.arupconsult.com.

Diarrhea, Acute Testing Algorithm

Clinical Background

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 greater than or equal to 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

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

Treatment

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

Entamoeba species

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

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

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

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

Treatment

Indicated in all cases

See Also

Celiac Disease

Clostridium difficile

Diarrhea, Bacterial Evaluation

Diarrhea, Viral Evaluation

Inflammatory Bowel Disease - IBD

Malabsorption

Algorithm(s)

PDF algorithm(s) available at www.arupconsult.com.

Diarrhea, Acute Testing Algorithm

Tests

Tests generally appear in the order most useful for common clinical situations

Test name: Giardia Antigen by EIA

ARUP #: 0060048

Methodology: Enzyme Immunoassay

Use:

First line testing for suspected parasitic diarrhea; rapid, 24-hour turnaround-time

Diagnose Giardia as etiology of diarrheal disease

Most sensitive method for detection of Giardia lamblia

Limitations:

Will not detect parasites other than G. lamblia

May require testing of multiple specimens

Test name: Giardia lamblia Antibody by IFA

ARUP #: 0099439

Methodology: Immunofluorescence Assay

Use:

First-line testing for suspected parasitic diarrhea; rapid, 24-hour turnaround time

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

Limitations:

Insensitive relative to stool EIA

Test name: Cryptosporidium Antigen by EIA

ARUP #: 0060045

Methodology: Enzyme Immunoassay

Use:

First-line testing for suspected parasitic diarrhea; rapid, 24-hour turnaround time

Diagnose Cryptosporidium as etiology of diarrheal disease

Most sensitive test for detection of Cryptosporidium spp

Limitations:

Will not detect parasites other than Cryptosporidium spp

May require testing of multiple specimens

Test name: Entamoeba histolytica Antigen, EIA

ARUP #: 0058001

Methodology: Enzyme Immunoassay

Use:

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

Limitations:

Rarely positive in extraintestinal disease

Will not detect parasites other than E. histolytica

May require testing of multiple specimens

Test name: Entamoeba histolytica (amebiasis), Antibody, IgG

ARUP #: 0050070

Methodology: Enzyme-Linked Immunosorbent Assay

Use:

Confirm past infection

Diagnose invasive extraintestinal disease

Limitations:

Preferred test for extraintestinal disease (eg liver abscess)

Test name: Parasitology Stain by Modified Acid-Fast

ARUP #: 0060046

Methodology: Concentration/Modified Acid-Fast Stain

Use:

Detect Cryptosporidium, Cyclospora and Isospora

Limitations:

Not intended for detection of other stool parasites
Less sensitive than EIA for Cryptosporidium spp

Test name: Microsporidia Stain

ARUP #: 0060050

Methodology: Modified Trichrome Stain

Use:

Detect Microsporidia

Limitations:

Not intended for detection of other stool parasites

Follow-up:

Test name: Ova & Parasite Exam, Fecal (Immunocompromised or Travel History)

ARUP #: 0060240

Methodology: Concentration Technique/Trichrome Stain/Microscopic Evaluation

Use:

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

Limitations:

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

Test name: Strongyloides Antibody, IgG by ELISA, Serum

ARUP #: 0099564

Methodology: Enzyme-Linked Immunosorbent Assay

Use:

Confirm clinical suspicion of Strongyloides infection in patient

Limitations:

Most sensitive test in chronic infections

Follow-up:

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 greater than or equal to 3 specimens over 10 days is recommended including request for special stains.

References

General References

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

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

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

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

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.

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

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

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

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

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

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

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

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

Viney ME, Lok JB. Strongyloides spp. WormBook. 2007;:1-15.

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

Medical Reviewers

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: September 2008