SummaryDifferences in the state of health between rural and urban populations living in Africa have been described, yet only few studies analysed inequities within poor rural communities. We investigated disparities in parasitic infections, perceived ill health and access to formal health services among more than 4000 schoolchildren from 57 primary schools in a rural area of western Cô te d'Ivoire, as measured by their socioeconomic status. In a first step, we carried out a cross-sectional parasitological survey. Stool specimens and finger prick blood samples were collected and processed with standardized, qualitycontrolled methods, for diagnosis of Schistosoma mansoni, soil-transmitted helminths, intestinal protozoa and Plasmodium. Then, a questionnaire survey was carried out for the appraisal of selfreported morbidity indicators, as well as housing characteristics and household assets ownership. Mean travel distance from each village to the nearest health care delivery structure was provided by the regional health authorities. Poorer schoolchildren showed a significantly higher infection prevalence of hookworm than better-off children. However, higher infection prevalences of intestinal protozoa (i.e. Blastocystis hominis, Endolimax nana and Iodamoeba bü tschlii) were found with increasing socioeconomic status. Significant negative associations were observed between socioeconomic status and light infection intensities with hookworm and S. mansoni, as well as with several self-reported morbidity indicators. The poorest school-attending children lived significantly further away from formal health services than their richer counterparts. Our study provides evidence for inequities among schoolchildren's parasitic infection status, perceived ill health and access to health care in a large rural part of Cô te d'Ivoire. These findings call for more equity-balanced parasitic disease control interventions, which in turn might be an important strategy for poverty alleviation.keywords access to health care, concentration index, Cô te d'Ivoire, health inequities, household assets ownership, parasitic infections

keywords Schistosoma mansoni, praziquantel, resistance correspondence Y.S. Liang, Jiangsu Institute of Parasitic Diseases, Meiyuan, Wuxi, Jiangsu 214064, P. R. China. The tolerance of Schistosoma mansoni to praziquantel has been reported in some endemic regions (Fallon et al. 1995; Stelma et al. 1995; Ismail et al. 1996; Guisse et al. 1997). To establish the reasons for clinical failures of praziquantel, a simple, quick and economic assay is required to detect resistance. Ideally this will involve the use of eggs or miracidia since these are the stages of the parasite life cycle which can easily be obtained from the faecal material of infected humans. As praziquantel causes changes in the shape of miracidia (Coles 1979), this was used as the basis for designing a test for resistance. In 24-well flat bottom microplates we observed the effect of praziquantel on miracidia hatched from eggs obtained from the faeces of mice infected with six isolates of S. mansoni. Two isolates were praziquantel-susceptible (one from Puerto Rico and one a mixture of isolates from Puerto Rico, Brazil, Egypt and Kenya), and four isolates were praziquantel-insusceptible, including a laboratory-selected praziquantel-resistant population (Fallon & Doenhoff 1994) and three Senegalese isolates. The cessation of swimming of miracidia was observed in different concentrations of praziquantel at various times and then the morphological changes were checked by adding a drop of Lugol's iodine. When the miracidia of both the susceptible and insuscep-tible isolates were exposed to 10-3 and 10-4 M praziquantel, they immediately contracted in the middle part of their bodies, giving the shapes of an unequal dumbbell or calabash, with the greater mass at the anterior end. In 5 10-6 M prazi-quantel 100% of miracidia from the susceptible isolates immediately changed shape, whereas only 11-15% of those from the insusceptible isolates did. Thus by addition of Lugol's iodine immediately after administering praziquantel, an objective measure of susceptibility could be obtained. After 1 minute in 10 6 M praziquantel 52% to 100% of susceptible miracidia had changed shape, and after 5 min 100% had done so compared with 3% to 15% and 9% to 18% of the insus-ceptible miracidia. Susceptibility could also be detected by determining whether miracidia had stopped swimming but this was less easy to read as a test than change in shape. By exposing freshly hatched miracidia to 10 6 M prazi-quantel and observing change in shape over one minute it should be possible to determine whether failed therapy is due to the presence of praziquantel-tolerant worms. It is planned to investigate this in field trials in China. The work was supported by the UNDP/World Bank/WHO Special Programmme for Research and Training in Tropical Diseases. References Coles GC (1979) The effect of praziquantel on Schistoma mansoni. Journal of Helminthology 53, 31-33. Fallon PG, Sturrock RF, Niang AC, Doenhoff MJ (1995) Short report: diminished susceptibility to praziquantel in a Senegal isolate of Sch...