Management of Strongyloides in Solid Organ Transplant Recipients

Key points

Epidemiology and risk factors

Strongyloides is present in temperate, tropical, and subtropical environments³ and is believed to infect as many as 30 to 100 million individuals globally.¹ In North America, Strongyloides is endemic to the southeast, particularly Appalachia,⁴ and to the Caribbean. Although the published studies confirming the presence of S stercoralis in the soil of Appalachia were performed in the 1980s,⁴ as recently as 2013, surveillance of 102 residents in rural Kentucky showed evidence of S stercoralis

Clinical manifestations

Strongyloides infection after solid organ transplantation may occur by (1) de novo acquisition via travel or residence in endemic areas after transplantation,¹⁰ (2) reactivation of disease in the recipient, or (3) donor-derived transmission. Reactivation of prior disease in the recipient is most common. Donor-derived strongyloidiasis typically presents early after transplantation, although there are some reports of diagnosis as late as 9 months after transplantation.¹¹ Reactivation disease

Host response to Strongyloides

Limited animal models have compromised our ability to understand the Strongyloides host–pathogen interaction. In rodents, S stercoralis penetrate skin, migrate to the lungs, and move to skeletal muscle.²⁶ Other species of Strongyloides—Strongyloides ratti and Strongyloides venezuelensis—also infect rodents, but lack an autoinfective cycle.²⁶ Thus, rodent models neither reproduce the intestinal phase of S stercoralis infection nor the autoinfective cycle seen in humans. Only severe combined

Diagnosis

At present, noninvasive diagnostic modalities include parasitologic and serologic tests for the diagnosis of S stercoralis. Unfortunately, the performance of existing noninvasive tests is not optimal. In addition, there are no pathognomonic radiologic findings to assist in diagnosis of S stercoralis.² The current reference standard, fecal microscopy, has limited sensitivity because there is only intermittent shedding of rhabditiform larvae into stool during the acute, chronic, or autoinfective

Screening strategies

Screening strategies for Strongyloides infection in the context of solid organ transplantation fall into 2 categories: (1) screening of the donor and (2) screening of the recipient. Screening is generally performed via commercial serology. Screening of donors and at-risk recipients is critical to the prevention of hyperinfection or dissemination syndromes after immunosuppression as well as to the rapid evaluation and initiation of appropriate therapy should S stercoralis infection disseminate

Summary

Infection with S stercoralis after organ transplantation carries a high mortality. A high index of suspicion is necessary to identify and treat patients with chronic infection owing to S stercoralis before the start of immunosuppression. Delayed diagnosis owing to imperfect diagnostics and limited alternative therapies to oral ivermectin render management of strongyloidiasis challenging. Recent advances in molecular diagnostics, newly identified preclinical therapeutic compounds with