Diagnosis of Strongyloides stercoralis species-specific repeat DNA in urine residue

LODH, N; SOIEFER, S; SCOTT, A; KROLEWIECKI, A; CARO, N; SHIFF, C

Alberta

Encuentro; The 91st Annual Meeting of the American Society of Parasitologists; 2016

American Society of Parasitologists

Recent work indicates that the prevalence of Strongyloides stercoralis infection is underestimated and of growing concern for immunosuppressed individuals. Most infections remain asymptomatic and difficult to identify. Standard parasitological tests of S. stercoralis rely on time-consuming culture based protocol to identify larvae in the stool. Although highly specific, this approach suffers from low sensitivity as larvae are produced sporadically. This may also be the case when fecal specimens are used for detection of parasite DNA. While antibody base detection methods can be sensitive, these can be problematic for the identification of ongoing infections. We have previously demonstrated that species-specific DNA can be detected in the urine of patients infected with Schistosoma haematobium or S. mansoni and that this approach is useful even when eggs cannot be detected in urine or feces, respectively. We have adapted these methods for detection of S. stercoralis DNA from urine samples. Fresh urine from infected and control individuals were collected locally and in Northern Argentina. The urine was filtered through filter paper, dried and individually sealed with desiccant and mailed for analysis. The DNA was extracted from filter papers and used to amplify a 125 base pair S. stercoralis repeat sequence using species-specific primers by PCR. The PCR products were visualized on agarose gel and sequenced to verify the repeat and to determine any sequence variation. The results from the urine analysis were compared to the outcome of standard parasitological analysis from the same individuals. Of the 100 urine samples analyzed, 52 were concordant (24 were positive in both feces and urine and 28 were negative for feces and urine), 41 were positive in the urine but negative in the feces and 7 were positive in the feces and negative for the urine analysis. The results suggest that detection of species-specific repeat DNA, which passed in the urine, could significantly enhance sensitivity for the identification of asymptomatic individuals infected with S. stercoralis.