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| {{SK}} Strongyloides Infection | | {{SK}} Strongyloides Infection |
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| == Overview == | | ==[[Strongyloidiasis overview|Overview]]== |
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| == Epidemiology and Demographics == | | ==[[Strongyloidiasis historical perspective|Historical Perspective]]== |
| Tropical and subtropical areas, but cases also occur in temperate areas (including the South of the United States). More frequently found in rural areas, institutional settings, and lower socioeconomic groups. <ref>http://www.dpd.cdc.gov/dpdx/HTML/Strongyloidiasis.htm</ref>
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| == Pathophysiology & Etiology== | | ==[[Strongyloidiasis pathophysiology|Pathophysiology]]== |
| The nematode (roundworm) Strongyloides stercoralis. Other Strongyloides include S. fülleborni, which infects chimpanzees and baboons and may produce limited infections in humans.
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| '''Life Cycle'''
| | ==[[Strongyloidiasis causes|Causes]]== |
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| [[Image:Strongyloides LifeCycle.gif|left|frame|Life cycle of Strongyloides stercoralis]] | | ==[[Strongyloidiasis differential diagnosis|Differentiating Strongyloidiasis from other Diseases]]== |
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| The Strongyloides life cycle is more complex than that of most nematodes with its alternation between free-living and parasitic cycles, and its potential for autoinfection and multiplication within the host. Two types of cycles exist:
| | ==[[Strongyloidiasis epidemiology and demographics|Epidemiology and Demographics]]== |
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| '''Free-living cycle:''' The rhabditiform larvae passed in the stool '''1''' can either molt twice and become infective filariform larvae (direct development) '''6''' or molt four times and become free living adult males and females '''2''' that mate and produce eggs '''3''' from which rhabditiform larvae hatch '''4''' . The latter in turn can either develop '''5''' into a new generation of free-living adults (as represented in '''2'''), or into infective filariform larvae '''6''' . The filariform larvae penetrate the human host skin to initiate the parasitic cycle '''6'''.
| | ==[[Strongyloidiasis risk factors|Risk Factors]]=== |
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| '''Parasitic cycle:''' Filariform larvae in contaminated soil penetrate the human skin '''6''' , and are transported to the lungs where they penetrate the alveolar spaces; they are carried through the bronchial tree to the pharynx, are swallowed and then reach the small intestine '''7''' . In the small intestine they molt twice and become adult female worms '''8''' The females live threaded in the epithelium of the small intestine and by parthenogenesis produce eggs '''9''' , which yield rhabditiform larvae. The rhabditiform larvae can either be passed in the stool '''1''' (see "Free-living cycle" above), or can cause autoinfection '''10''' . In autoinfection, the rhabditiform larvae become infective filariform larvae, which can penetrate either the intestinal mucosa (internal autoinfection) or the skin of the perianal area (external autoinfection); in either case, the filariform larvae may follow the previously described route, being carried successively to the lungs, the bronchial tree, the pharynx, and the small intestine where they mature into adults; or they may disseminate widely in the body. To date, occurrence of autoinfection in humans with helminthic infections is recognized only in Strongyloides stercoralis and Capillaria philippinensis infections. In the case of Strongyloides, autoinfection may explain the possibility of persistent infections for many years in persons who have not been in an endemic area and of hyperinfections in immunodepressed individuals.<ref>http://www.dpd.cdc.gov/dpdx/HTML/Strongyloidiasis.htm</ref>
| | ==[[Strongyloidiasis natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
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| ==Diagnosis== | | ==Diagnosis== |
| ===Symptoms===
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| ====Gastrointestinal====
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| *[[Abdominal Pain]]
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| *[[Diarrhea]].
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| ====Pulmonary====
| | [[Strongyloidiasis history and symptoms|History and Symptoms]] | [[Strongyloidiasis physical examination|Physical Examination]] | [[Strongyloidiasis laboratory findings|Laboratory Findings]] | [[Strongyloidiasis imaging findings|Imaging Findings]] | [[Strongyloidiasis other diagnostic studies|Other Diagnostic Studies]] |
| Pulmonary symptoms (including [[Loeffler’s syndrome]]) can occur during pulmonary migration of the filariform larvae.
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| ====Skin==== | | ==Treatment== |
| Dermatologic manifestations include urticarial rashes in the buttocks and waist areas. Disseminated strongyloidiasis occurs in immunosuppressed patients, can present with [[Abdominal Pain]], [[abdominal distension]], [[shock]], pulmonary and neurologic complications and [[septicemia]], and is potentially fatal.
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| ===Laboratory Findings===
| | [[Strongyloidiasis medical therapy|Medical Therapy]] | [[Strongyloidiasis surgery|Surgery]] | [[Strongyloidiasis prevention|Prevention]] | [[Strongyloidiasis cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Strongyloidiasis future or investigational therapies|Future or Investigational Therapies]] |
| ====Eosinophilia====
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| Blood eosinophilia is generally present during the acute and chronic stages, but may be absent with dissemination.<ref>http://www.dpd.cdc.gov/dpdx/HTML/Strongyloidiasis.htm</ref>
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| === Stool Smaples === | | ==Case Studies== |
| The diagnosis rests on the microscopic identification of larvae (rhabditiform and occasionally filariform) in the stool or duodenal fluid. Examination of serial samples may be necessary, and not always sufficient, because stool examination is relatively insensitive.
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| The stool can be examined in wet mounts:
| | [[Strongyloidiasis case study one|Case #1]] |
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| *directly
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| *after concentration (formalin-ethyl acetate)
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| *after recovery of the larvae by the Baermann funnel technique
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| *after culture by the Harada-Mori filter paper technique
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| *after culture in agar plates
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| The duodenal fluid can be examined using techniques such as the Enterotest string or duodenal aspiration. Larvae may be detected in sputum from patients with disseminated strongyloidiasis.
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| Rhabditiform larvae of Strongyloides stercoralis in wet mounts after fixation in formalin 10%. Diagnostic characteristics: length 200 to 250 µm (up to 380 µm); buccal cavity short, and prominent genital primordium.
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| [[Image:Strongyl larva1 DPDx.jpg|left|frame|A: Strongyloides stercoralis]] | |
| {{clr}}
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| '''A:''' The prominent genital primordium in the mid-section of the larva (black arrow) is readily evident. Note also the Entamoeba coli cyst (white arrow) near the posterior end of the larva.
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| ===Antibody Detection===
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| Immunodiagnostic tests for strongyloidiasis are indicated when the infection is suspected and the organism cannot be demonstrated by duodenal aspiration, string tests, or by repeated examinations of stool. Antibody detection tests should use antigens derived from Strongyloides stercoralis filariform larvae for the highest sensitivity and specificity. Although indirect fluorescent antibody (IFA) and indirect hemagglutination (IHA) tests have been used, enzyme immunoassay (EIA) is currently recommended because of its greater sensitivity (90%). Immunocompromised persons with disseminated strongyloidiasis usually have detectable IgG antibodies despite their immunodepression. Cross-reactions in patients with filariasis and some other nematode infections may occur. Antibody test results cannot be used to differentiate between past and current infection. A positive test warrants continuing efforts to establish a parasitological diagnosis followed by antihelminthic treatment. Serologic monitoring may be useful in the follow-up of immunocompetent treated patients: antibody levels decrease markedly within 6 months after successful chemotherapy. <ref>http://www.dpd.cdc.gov/dpdx/HTML/Strongyloidiasis.htm</ref>
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| == Treatment ==
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| === Pharmacotherapy ===
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| The drug of choice for the treatment of uncomplicated strongyloidiasis is ivermectin with albendazole as the alternative. All patients who are at risk of disseminated strongyloidiasis should be treated. (Albendazole is approved by the FDA, but considered investigational for this purpose).<ref>http://www.dpd.cdc.gov/dpdx/HTML/Strongyloidiasis.htm</ref>
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| ==References==
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| {{Reflist|2}}
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| {{WH}} | | {{WH}} |