Strongyloides stercoralislarvae excretion patterns before and after treatment

Abstract

The variability of larval excretion impedes the parasitological diagnosis of Strongyloides stercoralis in infected individuals. We assessed the number of larvae excreted per gram (LPG) stool in 219 samples from 38 infected individuals over 7 consecutive days before and in 470 samples from 44 persons for 21 consecutive days after ivermectin treatment (200 μg kg-1 BW). The diagnostic sensitivity of a single stool sample was about 75% for individuals with low-intensity infections (⩽1 LPG) and increased to 95% for those with high-intensity infections (⩾10 LPG). Doubling the number of samples examined per person increased sensitivity to more than 95%, even for low-intensity infections. There was no indication of a cyclic excretion of larvae. After treatment, all individuals stopped excreting larvae within 3 days. Larvae were not detected during any of the following 18 days (total 388 Baermann and 388 Koga Agar tests). Two stool samples, collected on consecutive days, are recommended in settings where low or heterogeneous infection intensities are likely. In this way, taking into account the possible biological variability in excretion, the efficacy of ivermectin treatment can be assessed as soon as 4 days after treatment.

Prevalence and risk factors of Strongyloides stercoralis in Takeo Province, Cambodia

“…Our study examined only a single stool sample per participant, thus the prevalence of S. stercoralis in our study setting was likely under-estimated, since the excretion of S. stercoralis larvae in stool specimens varies considerably from day-to-day [34,37]. A recent study showed that the output of larvae in faecal specimens ranged from 0.003 larvae per gram to 151.2 larvae per gram, as observed over seven consecutive days [37].…”

A case of strongyloidiasis in pregnancy

“…11 Postnatal resolution of excretion of strongyloides in the stools was an expected phenomenon, in coherence with a recently reported prospective study. 12 Strongyloidiasis in pregnancy cannot be taken lightly, because mortalities are still being reported.…”

Infection and Hyperinfection with Strongyloides stercoralis: Clinical Presentation, Etiology of Disease, and Treatment Options

“…A single stool exam yields positive results in, at best, 30-50 %. Examining up to three consecutive stool samples has been shown to improve sensitivity to up to 95 % [46]. Culture in an agar plate has a higher sensitivity (96 %); however, it is laborious and time consuming [47].…”

“…In patients at risk for hyperinfection, the sensitivity of stool examination is higher due to increased parasite load in the stools. In such cases, filariform larvae are more frequently found [46]. During the past decade, multiple immunological tests have been developed.…”