Abstract
BackgroundAfter alleged stop of transmission of schistosomiasis and further down the line in post elimination settings, sensitive tools are required to monitor infection status to prevent potential re-emergence. In Rahala, where transmission cycle of Schistosoma haematobium is interrupted since 2004 but where 30% of snails are still infected by S. bovis, potential human S. bovis infection can’t be excluded. As methods based on egg-counts do not provide the required sensitivity, antibody or antigen assays are envisaged as the most appropriate tools for this type of monitoring.MethodsIn this pilot study, the performances of three assays were compared: two commercially available antibody tests (ELISA and haemagglutination format) indicating exposure, and an antigen test (lateral flow strip format) demonstrating active infection. All 37 recruited study participants resided in Rahala (Akka, province Tata, Morocco). Participants had been diagnosed and cured from schistosomiasis in the period between 1983 and 2003. In 2015 these asymptomatic participants provided fresh clinical samples (blood and urine) for analysis with the aforementioned diagnostics tests.ResultsNo eggs were identified in the urine of the 37 participants. The haemagglutination test indicated 6 antibody positives whereas the ELISA indicated 28 antibody positives, one indecisive and one false positive. ELISA and haemagglutination results matched for 18 individuals, amongst which 5 out of 6 haemagglutination positives. With the antigen test (performed on paired serum and urine samples), serum from two participants (cured 21 and 32 years ago) indicated the presence of low levels of the highly specific Schistosoma circulating anodic antigen (CAA), demonstrating low worm level infections (less than 5 pg/ml corresponding to probably single worm pair). One tested also CAA positive with urine. ELISA indicated the presence of human anti-Schistosoma antibodies in these two CAA positive cases, haemagglutination results were negative.ConclusionsTo prevent reemergence of schistosomiasis in Morocco current monitoring programs require specific protocols that include testing of antibody positives for active infection by the UCP-LF CAA test, the appropriate diagnostic tool to identify Schistosoma low grade infections in travelers, immigrants and assumed cured cases. The test is genus specific will also identify infections related to S. bovis.
Highlights
After alleged stop of transmission of schistosomiasis and further down the line in post elimination settings, sensitive tools are required to monitor infection status to prevent potential re-emergence
In 2009 validation of interruption of transmission was commenced with the initiation of a national serological survey screening for human antibodies against S. haematobium in children, followed by a national molecular malacology survey analyzing the prevalence of infected snails
The results confirmed interruption of transmission and indicated progress towards elimination as it showed that none of children or the collected snails was infected by S. haematobium [5, 6]
Summary
After alleged stop of transmission of schistosomiasis and further down the line in post elimination settings, sensitive tools are required to monitor infection status to prevent potential re-emergence. In Rahala, where transmission cycle of Schistosoma haematobium is interrupted since 2004 but where 30% of snails are still infected by S. bovis, potential human S. bovis infection can’t be excluded. Effective transmission control of the infection includes accurate (high sensitivity) diagnosis, (preventive) chemotherapy, snail control, sanitation, safe water supplies, and human behavioral change strategies [3]. In 2009 validation of interruption of transmission was commenced with the initiation of a national serological survey (using enzymelinked immunoelectrotransfer blot, EITB) screening for human antibodies against S. haematobium in children, followed by a national molecular malacology survey analyzing the prevalence of infected snails (the intermediate host). It seems prudent to carefully monitor travelers and immigrants from endemic countries and other potentially high risk groups
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
