Strongyloidiasis Outside Endemic Areas: Long-term Parasitological and Clinical Follow-up After Ivermectin Treatment

REPETTO, SILVIA ANALIA; RUYBAL, PAULA; BATALLA, ESTELA I; LOPEZ, CARLOTA; FRIDMAN, VANESA; SIERRA, MARIELA; RADISIC, MARCELO; BRAVO, PABLO M; RISSO, MARIKENA G.; GONZALEZ-CAPPA, STELLA MARIS; ALBA SOTO, CATALINA D.

CLINICAL INFECTIOUS DISEASES

UNIV CHICAGO PRESS

Lugar: Chicago; Año: 2017

1058-4838

Background. Strongyloides stercoralis affects 30?100 million people worldwide. The first-line therapy is ivermectin. Cure isdefined as the absence of larvae by parasitological methods 1 year after treatment. To date, no longitudinal parasitological studiesfor longer periods of time have been conducted to confirm its cure. Here, we evaluated treatment response in long-term follow-uppatients with chronic infection using parasitological and molecular methods for larvae or DNA detection.Methods. A prospective, descriptive, observational study was conducted between January 2009 and September 2015 in BuenosAires, Argentina. Twenty-one patients with S. stercoralis diagnosis were evaluated 30, 60, and 90 days as well as 1, 2, 3, and/or 4 yearsafter treatment by conventional methods (fresh stool, Ritchie method, agar plate culture), S. stercoralis?specific polymerase chainreaction (PCR) in stool DNA, and eosinophil values.Results. During follow-up, larvae were detected by conventional methods in 14 of 21 patients. This parasitological reactivationwas observed starting 30 days posttreatment (dpt) and then at different times since 90 dpt. Eosinophil values decreased (P = .001)30 days after treatment, but their levels were neither associated with nor predicted these reactivations. However, S. stercoralis DNAwas detected by PCR in all patients, both in their first and subsequent stool samples, thus reflecting the poor efficacy of ivermectinat eradicating parasite from host tissues. Asymptomatic eosinophilia was the most frequent clinical form among chronically infectedpatients.Conclusions. These results suggest that the parasitological cure is unlikely. Strongyloidiasis must be considered a chronic infectionand ivermectin administration schedules should be reevaluated.