Schistosomiasis.

Schistosomiasis is a man-made disease related to water contact in the agricultural fields and affecting millions of people in developing countries in the tropical and subtropical parts of Africa, Asia and South America. It is a bisexual trematode living in the portal blood and perivesical venous plexus. Its life cycle necessitates the presence of an intermediate host - a fresh water mollusc - that differs according to place. The pathogenetic stage is the ova that initiate an immunologically delayed hypersensitivity cell-mediated reaction in the organs where they are deposited. The liver, colon, urinary bladder and ureter are the main organs affected; however, any organ can be affected, even the skin and the brain. The review discusses the pathogenesis, pathology, diagnosis: parasitological and immunological, the clinical picture, treatment and control. The present status of the research work on vaccination is also presented.

Detection of circulating anodic antigen before and after specific chemotherapy in experimental murine Schistosomiasis mansoni.

In two groups of mice infected with 60 (group I) and 120 (group II) Schistosoma mansoni cercariae, respectively, the effects of intensity and duration of infection, and of praziquantel therapy (curative vs subcurative dose) on the levels of circulating anodic antigen (CAA), were studied. CAA was measured in trichloracetic acid-treated serum samples with an avidin-biotin enzyme-linked immunosorbent assay (AB-ELISA) using the monoclonal anti-CAA antibody. Total worm burdens, oogram patterns and ova counts/g liver and intestine were followed up. The lowest detectable level of CAA was about 1.0 ng/ml, and was positive with a worm load of 3-5/mouse. CAA levels became already detectable as early as 1-2 weeks post-infection (pi) before any parasitological parameter and showed a significant drop from the 11th-12th week pi onwards. A positive correlation was demonstrated between the CAA level and worm load. Following successful praziquantel therapy, CAA disappeared earlier than any of the other parameters studied.

Effect of specific chemotherapy on the immune response and resistance to reinfection in experimental Schistosomiasis mansoni.

Mice infected for 45 days with 120 Schistosoma mansoni cercariae and treated with praziquantel in a dose of 500 mg/kg for two consecutive days had a significant lower resistance to reinfection when challenged two weeks after treatment (45% compared to 88% in infected challenged untreated mice). In praziquantel-treated mice, the reduction in the per cent resistance was accompanied by a diminution in the size of hepatic granulomata and its in vivo correlate the delayed foot pad swelling. Moreover, the granuloma proportionate T-cell subset enumeration revealed a significant reduction in the number of T-helper cells. The humoral immune response as measured by the immediate foot pad swelling was not affected by praziquantel. Results reveal besides the diminution of the state in resistance to reinfection after praziquantel, possible involvement of egg-related pathology as a T-cell mediated reaction and as a mechanical obstacle in maintenance of this resistance.