Malaria and schistosomiasis risks associated with surface and sprinkler irrigation systems in Zimbabwe.

A comparative assessment of the malaria and schistosomiasis risks associated with surface and sprinkler irrigation systems in Zimbabwe was carried out. The risk assessment of the two diseases was done in accordance with the three standard components of health impact assessment, namely (i) community vulnerability, (ii) environmental receptivity, and (iii) capability of health services to respond to malaria and schistosomiasis. Records of the two diseases were obtained from four health centres serving two surface irrigation schemes and two sprinkler irrigation schemes. For comparison records were also obtained from health centres serving nearby dryland areas. Incidence of schistosomiasis as estimated from recorded new cases of the disease was much higher in surface irrigation schemes than in sprinkler irrigation schemes. For malaria it was the other way around. These findings were confirmed by rapid risk assessments. Malaria risk factors were more prominent in sprinkler irrigation schemes, whereas more schistosomiasis risk factors were identified in surface irrigation schemes. These observations were attributed to poorly maintained infrastructure and inadequate landscape-levelling, which created mosquito breeding sites within the fields in the case of sprinkler schemes, and to poor drainage structures, which created snail-breeding sites in the case of surface-irrigation schemes. Importantly, poor maintenance of sprinkler scheme infrastructure accounted for more disease promoting features than the engineering designs per se. This study demonstrated the value of complementing routinely collected health data with rapid assessment procedures for appraisal of commonly reported diseases.