Sodium hypochlorite (NaOCl), electrochemically derived from sodium chloride solution, is the most convenient source of active oxygen. The high reactivity and non-specificity of NaOCl open ample scope for its wide medical application. The objective of this in vitro experiment is to examine the efficacy of NaOCl (1 and 10 ppm) against adult Schistosoma mansoni using scanning electron microscopy (SEM). The tolerance against NaOCl was determined by scoring the worm motility after 3, 6, 12 and 24 hours of incubation. In 1 ppm NaOCl-treated group, 60 % of worms significantly collapsed and moved only parts of the body 3 hours post-incubation, 30 % became immobile after 12 hours and 60 % died after 24 hours. The motility of worms in 10 ppm NaOCl-treated group decreased with longer exposure, and all worms died after 24 hours of incubation. SEM revealed that NaOCl induced extensive tegumental damage. After treatment with 1 ppm of NaOCl, the male tegument showed slight to moderate peeling. There were also marked changes in the tubercles, where some were swollen and others showed shortening of the spines. A large number of blebs were observed on the surface of the tubercles, and some were disrupted. Tegumental damage became more apparent after treatment with 10 ppm of NaOCl, where it showed extensive peeling and erosion, and some of the tubercles showed shortening and complete loss of spines. The results suggest that NaOCl-induced lesions in the schistosome tegument may increase the tegument antigenicity through exposure of its surface antigens, allowing the host's immune system to function effectively against the worm. This may provide a further insight for rational design of novel complementary chemotherapeutic or vaccine strategies for the control of schistosomiasis.
Key words: Adult Schistosoma mansoni, tegument, sodium hypochlorite, scanning electron microscopy
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