Diagnosis of Strongyloides stercoralis infection by detecting repeat DNA from urine

LODH, N; CARO, RN; SHIFF, C; SCOTT, A; JUAREZ, M; CANABIRE, M; CAJAL SP; KROLEWIECKI, A

Filadelfia

Encuentro; 64th Annual Meeting of the American Society of Hygiene & Tropical Medicine; 2015

American Society of Hygiene & Tropical Medicine

Recent work indicates that the prevalence of Strongyloides stercoralis infection is underestimated and of growing concern for immunosuppressed individuals. Most infections with S. stercoralis are asymptomatic and difficult to identify. Standard parasitological diagnosis of S. stercoralis relies on time consuming culture-based protocol to identify larvae in the stool. Although highly specific, this approach suffers from low sensitivity as larvae are only produced sporadically and thus low-level infections are often missed. While antibody-base detection methods can be sensitive, this approach is 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 demonstrated in urine or feces, respectively. We have adapted these methods for the detection of S. stercoralis DNA from urine samples. Fresh urine samples from infected and control individuals were collected locally and in Northern Argentina from individuals participating in a community intervention. The parasite DNA was concentrated on filter paper which was dried at room temperature, sealed with desiccant and mailed for analysis. The DNA was extracted from the filters and used as the template to amplify a 125 base-pair S. stercoralis repeat sequence using the polymerase chain reaction. The PCR products were visualized on a 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 30 urine samples analyzed, 18 were concordant (13 were positive in both feces and urine and 5 were negative for feces and urine), 9 were positive in the urine but negative in the feces and 3 were positive in the feces and negative for the urine analysis. The results suggest that PCR-based detection of repeat DNA passed in the urine could significantly enhance sensitivity for the identification of individuals actively infected with S. stercoralis.