eMedicine Specialties > Infectious Diseases > Gastrointestinal Tract and Intra-abdominal Infections

Strongyloidiasis: Differential Diagnoses & Workup

Author: Pranatharthi Haran Chandrasekar, MD, Director of Infectious Disease Fellowship, Professor, Department of Internal Medicine, Harper Hospital, Wayne State University School of Medicine
Coauthor(s): Ramesh A Bharadwaj, MD, Fellow in Infectious Diseases, Detroit Medical Center, Wayne State University; Hari Polenakovik, MD, Assistant Professor of Medicine, Wright State University Boonshoft School of Medicine, Dayton, OH; Sylvia Polenakovik, MD, Clinical Instructor, Internist, Department of Internal Medicine, Wayne Hospital, Wright State University
Contributor Information and Disclosures

Updated: Apr 3, 2009

Differential Diagnoses

Acute Respiratory Distress Syndrome
Malabsorption
Ascariasis
Meningitis
Asthma
Peptic Ulcer Disease
Diverticulitis
Pneumonia, Bacterial
Eosinophilia
Sepsis, Bacterial
Eosinophilic Gastroenteritis
Septic Shock
Gastroenteritis, Bacterial
Upper Gastrointestinal Bleeding
Ileus
Urticaria
Inflammatory Bowel Disease
Intra-abdominal Sepsis
Lower Gastrointestinal Bleeding

Workup

Laboratory Studies

  • CBC count with differential
    • WBC count is usually within the reference range in acute and chronic strongyloidiasis; it is often elevated in severe strongyloidiasis.
    • Eosinophilia (>600/mL) is common during acute infection, intermittent during chronic infection, and frequently absent in severe strongyloidiasis.
    • Suspect and evaluate for strongyloidiasis in any patient who presents with persistent, mild, or moderate-to-high eosinophilia and who has lived in or traveled to an area endemic for S stercoralis.
  • Stool for ova and parasites
    • Microscopically identify S stercoralis larvae (definitive diagnostic test).
    • Ova are almost never observed during a strongyloidiasis infection; results from this examination are typically negative during acute infection.
    • Examine stool directly in wet mounts (very low yield) or after ethyl acetate-formalin concentration occurs.

      Rhabditiform larva of <EM>Strongyloides stercoral...

      Rhabditiform larva of Strongyloides stercoralis in stool specimen (wet mount stained with iodine).

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      Rhabditiform larva of <EM>Strongyloides stercoral...

      Rhabditiform larva of Strongyloides stercoralis in stool specimen (wet mount stained with iodine).

    • Single stool examination yields a low sensitivity (approximately 30%) in chronic strongyloidiasis because larval output is low and intermittent. Perform at least 3 stool examinations on consecutive days because this may increase the sensitivity to 70-80%.
    • To establish a diagnosis, enhance larvae recovery by using special methods such as the Baermann funnel method, the Harada-Mori filter paper method, and the agar plate method, when needed. The latter appears to be the most sensitive and efficient method.
    • Obtain blood cultures in all patients presenting with possible severe strongyloidiasis. Blood cultures often yield growth of enteric pathogens, most commonly Escherichia coli and/or Klebsiella species.
  • Strongyloides serology (eg, enzyme immunoassay, indirect fluorescent antibody)
    • With 88-95% sensitivity, it is the most sensitive test for detecting strongyloidiasis in immunocompetent patients. Sensitivity may be lower in severely immunocompromised patients, however, and this test cannot be used to differentiate between past and present infection.
    • If results are positive, continue efforts to establish a parasitologic (microscopic) diagnosis because of cross-reactivity with other nematode infections (8-16%).
    • This test is also useful for monitoring a patient's response to therapy (antibody titers decrease markedly within 6-12 mo of successful therapy).
  • Sputum cultures: These occasionally suggest Strongyloides infection; when observing the agar plate, the microorganisms that are part of the normal respiratory flora may be found outside the area of streaking as groups of colonies arranged in a characteristic pattern. This laboratory phenomenon is a result of migrating larvae on the agar plates, and, in an appropriate clinical setting, is considered diagnostic of S stercoralis infection.

Imaging Studies

  • Obtain a chest radiograph to reveal possible patchy alveolar infiltrates in acute strongyloidiasis. In severe strongyloidiasis, findings are diverse; the chest radiograph may depict diffuse interstitial infiltrates, segmental or diffuse alveolar infiltrates, or pleural effusions.
  • A plain abdominal radiograph may reveal loops of a dilated small bowel, or ileus, in severe strongyloidiasis.
  • Barium swallow and barium enema findings may be normal, may exhibit bowel dilatation, or may indicate stenosis with ulceration.
  • Obtain a CT scan of the abdomen and pelvis to reveal any nonspecific thickening of the bowel wall.

Procedures

  • Findings from upper and lower gastrointestinal endoscopy may range from normal-appearing mucosa to severe duodenitis and colitis. The most common abnormal duodenal endoscopic finding is edematous mucosa, white villi, and erythematous mucosa. In some cases, the larvae are identified with duodenal biopsy.7
  • Conduct an Enterotest (string test) or duodenal aspiration to examine duodenal fluid for Strongyloides species larvae. These tests produce more positive results than a stool examination.
  • Perform sputum examinations, bronchial washings, and bronchoalveolar lavages in cases of severe strongyloidiasis. These procedures frequently reveal filariform and/or rhabditiform larvae.
  • Perform a lumbar puncture if CNS involvement is suspected.
    • Perform cerebrospinal fluid analysis (elevated protein levels, decreased glucose levels, pleocytosis with neutrophilic predominance) to evaluate for acute bacterial meningitis.
    • A Gram stain may exhibit gram-negative rods or, rarely, gram-positive cocci in chains (Enterobacteriaceae, Streptococcus species).
    • A wet mount preparation may reveal S stercoralis larvae.

Histologic Findings

S stercoralis larvae are typically found in the proximal part of the small intestine, embedded in the mucosal lamina propria, where they produce mild-to-moderate degrees of edema, cellular infiltration, partial villous atrophy, and, occasionally (in severe strongyloidiasis), ulcerations. In long-standing infections, fibrosis may develop.

More on Strongyloidiasis

Overview: Strongyloidiasis
Differential Diagnoses & Workup: Strongyloidiasis
Treatment & Medication: Strongyloidiasis
Follow-up: Strongyloidiasis
Multimedia: Strongyloidiasis
References
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Further Reading

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Keywords

strongyloidiasis, hyperinfection syndrome, disseminated strongyloidiasis, Strongyloides, threadworm infection, Cochin China diarrhea, parasitic nematodes, Strongyloides stercoralis, S stercoralis, Strongyloides fuelleborni, S fuelleborni, bacterial meningitis, rhabditiform larvae, parthenogenesis, filariform, bacteremia, Escherichia coli, E coli, Klebsiella species, helminth, strongyloidosis, acute strongyloidiasis, chronic strongyloidiasis, intestinal strongyloidiasis

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Contributor Information and Disclosures

Author

Pranatharthi Haran Chandrasekar, MD, Director of Infectious Disease Fellowship, Professor, Department of Internal Medicine, Harper Hospital, Wayne State University School of Medicine
Pranatharthi Haran Chandrasekar, MD is a member of the following medical societies: American College of Physicians and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Coauthor(s)

Ramesh A Bharadwaj, MD, Fellow in Infectious Diseases, Detroit Medical Center, Wayne State University
Ramesh A Bharadwaj, MD is a member of the following medical societies: American College of Physicians and Michigan State Medical Society
Disclosure: Nothing to disclose.

Hari Polenakovik, MD, Assistant Professor of Medicine, Wright State University Boonshoft School of Medicine, Dayton, OH
Hari Polenakovik, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Sylvia Polenakovik, MD, Clinical Instructor, Internist, Department of Internal Medicine, Wayne Hospital, Wright State University
Sylvia Polenakovik, MD is a member of the following medical societies: American College of Physicians-American Society of Internal Medicine and American Medical Association
Disclosure: Nothing to disclose.

Medical Editor

Wesley W Emmons, MD, FACP, Assistant Professor, Department of Medicine, Thomas Jefferson University; Consulting Staff, Infectious Diseases Section, Department of Internal Medicine, Christiana Care, Newark, DE
Wesley W Emmons, MD, FACP is a member of the following medical societies: American College of Physicians, American Medical Association, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, and International AIDS Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Ronald A Greenfield, MD, Professor, Department of Internal Medicine, Section of Infectious Diseases, University of Oklahoma College of Medicine
Ronald A Greenfield, MD is a member of the following medical societies: American College of Physicians, American Federation for Medical Research, American Society for Microbiology, Central Society for Clinical Research, Infectious Diseases Society of America, Medical Mycology Society of the Americas, Phi Beta Kappa, Southern Society for Clinical Investigation, and Southwestern Association of Clinical Microbiology
Disclosure: Pfizer Honoraria Speaking and teaching; Gilead Honoraria Speaking and teaching; Ortho McNeil Honoraria Speaking and teaching; Wyeth Honoraria Speaking and teaching; Abbott Honoraria Speaking and teaching; Astellas Honoraria Speaking and teaching; Cubist  Speaking and teaching

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

 
 
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