Recent trends in the prevalence and distribution of schistosomiasis in the Nile delta region.

In 1983, a survey of 71 villages in the Nile delta demonstrated that the overall prevalence of Schistosoma mansoni and S. haematobium infections was 39% and 5%, respectively. Recent increased availability of praziquantel, combined with Egyptian Ministry of Health-sponsored media efforts to educate the public about schistosomiasis, prompted us to determine the current status of S. mansoni and S. haematobium infections in the delta and evaluate any changes that may have occurred since the previous survey. The same villages that participated in the 1983 survey were resampled in 1990. Stool and urine samples were requested from all occupants over the age of two years in a 5% sample of houses within each village. Stool (Kato) thick smears and urine sediments were read qualitatively at the rural health station. Field-prepared Kato smears and a 20% sample of urine specimens were forwarded to the Ministry of Health Laboratory, where quantitative readings were also performed. Analysis of samples obtained from 17,310 persons revealed that S. mansoni prevalence had decreased to 23% and that S. haematobium prevalence had decreased to 3% (P < 0.001). The highest levels of schistosome infection were found in governates located in the eastern section of the delta. The observed changes in the prevalence of S. mansoni and S. haematobium suggest that control measures are having a favorable impact on schistosomiasis transmission in this region.

Immune responses and immunoregulation in relation to human schistosomiasis in Egypt. I. Effect of treatment on in vitro cellular responsiveness.

Cell mediated immune reactivity of chronic schistosomiasis patients was tested in vitro by peripheral blood mononuclear cell (PBMN) responses against phytohemagglutinin P (PHA), Candida albicans extract, soluble schistosomal antigenic preparations derived from eggs (SEA), adult worms (SWAP) and cercariae (CAP), before and after treatment of the patients with parziquantel. The patient population was from villages in the Qalyub province, Egypt, that are endemic for Schistosoma mansoni and S. haematobium. Patients were studied immediately before, and at 1, 3, 6, and 9 months after chemotherapy. Egg counts were done on stool and urine specimens taken simultaneously with blood samples. There was a significant increase in PBMN responses to SWAP and CAP but not to SEA, PHA or C. albicans in 27 patients (age 8-65) 1 month after treatment. Eleven patients treated 1.5 years previously did not show such elevated responses 1 month after re-treatment. Three months after treatment higher mean responses were observed to SWAP, CAP, SEA, and PHA, but not to C. albicans in 24 patients (age 6-26). Significant increases in PBMN responses to SWAP and CAP, but not to SEA, PHA or C. albicans were obtained at 6 months after treatment in 12 patients (age 6-30). By 9 months after treatment in a group of 11 patients (age 8-25) SWAP and CAP responses were still elevated as were SEA and C. albicans induced reactivities. The PBMN responses of 10 patients were followed longitudinally at pretreatment, 3-, 6-, and 9-month post-treatment times. In general, elevated responses were maintained throughout this period to the schistosomal preparations. Unrelated responses occasionally fluctuated but were not consistently altered over time.

Immune responses and immunoregulation in relation to human schistosomiasis in Egypt. II. Cimetidine reversal of histamine-mediated suppression of antigen-induced blastogenesis.

The effect of histamine on cell-mediated immune responses of chronic schistosomiasis patients was tested by peripheral blood mononuclear cell (PBMN) reactions to phytohemagglutinin-P (PHA) and soluble schistosomal antigenic preparations derived from eggs (SEA) or adult worms (SWAP). PBMN responses to PHA were suppressed by exogenous histamine (10(-5)M), and the addition of cimetidine (CIM) (10(-4)M), an H2-receptor antagonist, reversed this suppressive effect. Histamine primarily suppressed PBMN responses to suboptimal and optimal PHA concentrations. Exogenous histamine (10(-5)M) also suppressed PBMN responses of 27 schistosomiasis patients to SEA and SWAP, respectively. The addition of CIM (10(-4)M) to suppressed cultures reversed the effect of exogenous histamine. Most importantly, the addition of CIM to schistosomal antigen-induced cultures, without exogenous histamine, significantly increased patients' PBMN responses to SEA and SWAP. The mean optimal increase in SEA responses of 19 patients was 390%. With SWAP-induced responses of 21 patients this increase was 165%. The use of 10(-4)M diphenhydramine (DPH), an H1-receptor antagonist, resulted in general suppression of both PHA-induced and schistosomal antigen-induced PBMN responses. Lower concentrations of DPH lead to variable responses but did not result in consistent abrogation of the histamine-induced suppression. These data imply that an histamine-induced, H2-receptor-mediated suppressor circuit often helps modulate antigen-specific responsiveness of PBMN from patients with chronic schistosomiasis.