Rainfall, irrigation and malaria transmission. In the Ziway area of central Ethiopia where irrigation schemes have improved the lives of the peo- ple, Kibret et al (2010) found that the abundance of A. pharoensis was significantly higher than that of A. arabiensis during the dry irrigated period of the year. They also observed that canal leakage pools, irrigated fields and irrigation canals were the major breeding habitats. Larval and adult abundance of the malaria vectors, A. pharoensis, was higher in the irrigated than in the non- irrigated village throughout the period of study. P. falciparum sporozoite infection rates of 0.66% were determined in A. pharoensis in the irrigated village. Peak biting activities of A. pharoensis oc- curred before 22:00 h, which is a source of concern that the effectiveness of ITNs may be com- promised as the mosquitoes feed on blood before people go to bed. The area receives between 700 and 800 mm of annual rainfall, with the main rains from June to September and short rains in April and May. The mean annual temperature is 200C. Malaria transmission in Ziway is generally unstable and seasonal, with peak transmission between September and November, immediately after the main rainy season and a secondary transmission period between April and May in the short rainy season. P. falciparum is the most prevalent malaria parasite, responsible for 60–70% of malaria cases, followed by P. vivax (Xxxxx et al. 1998b). However, there are increasing levels of malaria prevalence in the dry season as a result of A. pharoensis breeding all year round in the irrigation area.
