STUDIES ON SCHISTOSOMIASIS IN WESTERN KENYA .1. EVIDENCE FOR IMMUNE-FACILITATED EXCRETION OF SCHISTOSOME EGGS FROM PATIENTS WITH SCHISTOSOMA-MANSONI AND HUMAN-IMMUNODEFICIENCY-VIRUS COINFECTIONS

Persons employed as vehicle washers in the town of Kisumu, Kenya are e xposed for several hours each day to water in Lake Victoria that conta ins Schistosoma mansoni-infected Biomphalaria pheifferi snails. This r esults in a focus of high endemicity for schistosomiasis and these per sons have very high concentrations of eggs in their feces (mean +/- SD = 1,469 +/- 1,581 eggs per gram [EPG] of feces). Fecal egg counts, bu t not circulating cathodic antigen (CCA) levels, in these schistosomia sis patients differed strikingly based on the patient's seropositivity for human immunodeficiency virus (HIV). Patients who were infected wi th S. mansoni and were seropositive for HIV had similar levels of CCA but excreted fewer eggs (643 +/- 622 EPG; n = 16) than individuals who were not seropositive for HIV infection (1,891 +/- 1,779 EPG; n = 37) (P = 0.009). Egg excretion ratios (EPG/CCA) of the seronegative group were also significantly higher than those of the seropositive group. Those in the seropositive group showed a significant correlative relat ionship between egg excretion ratios and CD4(+) lymphocyte percentages . These observations are compatible with the hypothesis that schistoso me eggs exit the human host through the requisite facilitation of func tional immune responses, and that the efficacy of this process decreas es in schistosomiasis patients co-infected with HIV as their periphera l blood CD4(+) cell levels decrease.