Approach Considerations
All persons found to harbor Strongyloides organisms should be treated, even if they are asymptomatic, because of the risk for hyperinfection. However, for infected pregnant patients, clinicians may wish to defer treatment for strongyloidiasis until after the first trimester. All of the anthelmintic medications discussed in this article are US Food and Drug Administration (FDA) category C agents.
Strongyloides species are the hardest worms to eradicate. Treatment of early infection is with symptomatic support, because specific therapy is more effective once intestinal infection is established. Posttherapy stool examinations at 6 months and 12 months posttreatment are recommended to verify Strongyloides eradication and to exclude other parasitic infections. [71] A posttreatment/pretreatment ratio of 0.6 or less suggests successful treatment. Patients with hyperinfection should undergo multiple followup stool examinations starting at 2 weeks posttreatment. [72]
Empiric corticosteroid administration used to treat wheezing is problematic, because it may cause life-threatening hyperinfection. Thus, Strongyloides hyperinfection syndrome, usually precipitated by immune suppression, should be considered in patients who have resided in endemic regions. [73] Attempts at the detection and eradication of this infection are recommended to prevent this potentially fatal complication.
Surgical intervention may be required in the rare instance of acute abdominal symptoms (peritonitis) due to bowel obstruction or infarction in the context of severe strongyloidiasis.
Intensive care and transfer
Immunocompromised hosts may require hospitalization and intensive care in disseminated infection. Consider contact isolation in these patients, because sputum, stool, vomitus, and other bodily excreta may contain infective (filariform) larvae.
Patients with hyperinfection syndrome often have complications of sepsis, shock, and acute respiratory distress syndrome (ARDS). Any patient suspected of disseminated disease should receive care in a facility properly equipped for intensive management.
Anthelmintic Therapy
Strongyloides infection should be suspected in a patient with nonspecific gastrointestinal, respiratory, or recurrent dermatologic symptoms of unclear etiology with risk factors for Strongyloides infection. Conduct definitive treatment with anthelmintic drugs, although these medications target adult worms and are not very effective against larvae in the initial infection.
Strongyloides infections should be treated even in the absence of symptoms as hyperinfection syndrome carries a high mortality rate. Disseminated strongyloidiasis requires treatment for at least 7 days or until the parasite can no longer be identified in clinical specimens. Concomitant infections should be treated aggressively, and any immunosuppressants, including exogenous corticosteroids, should be quickly tapered. [74] Corticosteroid therapy must be avoided, because hyperinfection and death may occur.
Anthelmintic treatment may have to be repeated or the duration prolonged in patients with hyperinfection syndrome. Relapses may occur despite proper therapy.
Anthelmintic agents
For acute and chronic strongyloidiasis, the CDC recommends ivermectin 200 μg/kg daily orally for 1 day to 2 days as first-line therapy. Relative contraindications include concomitant Loa loa infection, weight less than 15 kg, pregnancy, and breastfeeding. Alternatively, albendazole 400 mg orally twice a day for 1 week can be given. Relative contraindications include hypersensitivity to benzimidazole compounds and first trimester of pregnancy. [75] A 2016 meta-analysis of seven trials found that ivermectin was more efficacious than albendazole and better tolerated than thiabendazole. Cure rates for ivermectin, albendazole, and thiabendazole were 74% to 84%, 48%, and 69%, respectively. [76] The main issue with thiabendazole was GI side effects. [77]
Patients with hyperinfection and disseminated disease should be treated with ivermectin 200 μg/kg per day orally until stool and/or sputum examination findings are negative for 2 weeks. Rectal administration is recommended for patients with malabsorption or who are unable to tolerate oral therapy. Every effort should be made to reduce or stop immunosuppressants in these patients. [75]
Patients in whom treatment fails to elicit a response should undergo screening for HTLV-1 infection. [78]
Antibiotic Therapy and Supportive Care
Provide antibiotic therapy directed toward enteric pathogens if bacteremia or meningitis is present or suggested; treat such bacterial complications for 2 weeks to 4 weeks with antibiotics according to the results of in vitro testing against the bacterial isolate(s).
Provide supportive treatment as indicated (eg, intravenous fluids if volume depletion, blood transfusion if gastrointestinal or alveolar hemorrhage, mechanical ventilation if respiratory failure). Symptomatic treatment should be initiated. Pruritic dermatologic manifestations should be treated with antihistamines. Inhaled beta-agonists may improve wheezing; steroids should be avoided as they will worsen the infection. The use of leukotriene synthesis inhibitors for wheezing may also worsen infection, because leukotrienes are shown to play a potential role in the immunity against Strongyloides infection.
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First stage, life cycle of Strongyloides stercoralis. Illustration by Tessa Kalman.
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Second stage, life cycle of Strongyloides stercoralis. Illustration by Tessa Kalman.
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Third stage, life cycle of Strongyloides stercoralis. Illustration by Tessa Kalman.
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Fourth stage, life cycle of Strongyloides stercoralis. Illustration by Tessa Kalman.
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Fifth stage, life cycle of Strongyloides stercoralis. Illustration by Tessa Kalman.
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Rhabditiform larva of Strongyloides stercoralis in stool specimen (wet mount stained with iodine).
