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Keywords:

  • canal cleaners;
  • Schistosoma mansoni;
  • whole worm homogenate;
  • cercarial homogenate

The present work was a longitudinal study on Schistosoma mansoni infection in occupationally hyperexposed canal cleaners in the Sudan and the influence of therapy on the parasitological and humoral immune parameters. Chronically infected canal cleaners (n=28) were more resistant to reinfection (Fisher's exact test, P<0.05) than newly recruited canal cleaners (n=17). Chronically infected canal cleaners had a significantly higher degree of Symmers' fibrosis (χ2=19.1, P<0.0001), significantly larger portal vein diameter (P<0.05) and enlarged spleen (χ2=4.2, P<0.05) than recently infected, newly recruited canal cleaners. ELISA was used to detect IgG, IgA and IgM in response to whole worm homogenate (WWH) and cercarial homogenate (CH). Chronically infected canal cleaners had significantly higher IgG to WWH antigen than newly recruited canal cleaners and normally exposed individuals (P<0.05), while both chronically infected and newly recruited canal cleaners had higher IgG levels to CH antigen than normally exposed individuals (P<0.05). The newly recruited canal cleaners had a significantly higher IgM level to CH antigen than chronically infected canal cleaners (P<0.05). The IgG level to WWH antigen increased significantly after treatment in newly recruited canal cleaners and normally exposed individuals (P<0.05). The IgA level to CH antigen increased significantly after treatment in the chronically infected group (P<0.05). Comparison of the serological parameters between the different study groups with regards to infection and treatment is discussed.