The Potential of in situ Rain Water Harvesting for Water Resources Conservation on Malaria Transmission in Tigray, Northern Ethiopia

Abstract

The role of in situ rain water harvesting (RWH) in water resources conservation is well recognized in semiarid areas, such as the highlands of northern Ethiopia. However, in fringe areas of malaria endemicity, the potential impact of such schemes on vector populations and malaria transmission is not well documented. We therefore investigated the impact of such environmental interventions on Anopheles vector breeding and malaria burden, in a cross sectional survey undertaken in March/April 2005 in 4 villages in northwestern (3 in Hadegti and Hibret subdistricts; (s.d) 1800masl.) and central (Endachewa s.d.; 2050masl) zones of Tigray, in northern Ethiopia, where large scale construction of half-moon ponds (HMP) and ditches was in progress. A total of 990 blood slides taken from under 10 children revealed 268 infections of which 90.7% were P. falciparum, 7.5% P. vivax and 1.9% mixed. All of these were from Hadegti and Hibret s.d. where HMPs predominated, revealing a slide positivity rate of 35.6% (range 30.7 – 41.7%) and 3.6%, respectively. The majority (>77%) of the malaria positive cases resided in households located within 750 meters of the RWH structures, indicating that proximity to mosquito breeding sites was an important determinant of malaria in the villages. Over 33.8 % of the aquatic habitats in these villages were colonized by Anopheles aquatic stages, of which all were identified morphologically as An. gambiae sensu lato (presumably An. arabiensis). HMPs were found to be more productive than the smaller ditches, where water stayed longer for the aquatic stages to reach maturity to the adult mosquito. Hence, such environmental interventions require due consideration and need to be integrated with appropriate malaria control strategies.

Key words: In situ Rain water harvesting, Malaria, Anopheles arabiensis, Tigray, Ethiopia.