Characterisation of the spatial prevalence and contribution of malaria to paddy rice yield loss in Bugiri district

Malaria is one of the water related diseases that is believed to reduce the available labour in agriculture especially in the paddy rice farming systems which serve as breeding grounds. The breeding habitats, their bio-physical properties and the effect of malaria on rice yields are, however, not well characterised. This research work aimed at identifying and characterising the anopeheles mosquito breeding habitats' bio-physical properties. It also aimed at establishing the effect relationship between malaria induced labour losses and paddy rice yields. The study was conducted in Nankoma, Nabukalu and Buluguyi sub-counties in Bugiri district, a paddy rice growing system in Eastern Uganda. Data for habitat identification and characterization, was collected every after 25 days for a period of one year (June 2005 to June 2006). Shallow skim dipping method was used to sample the anopheles mosquito larvae from breeding habitats. Habitats were characterised for water temperature, pH, oxygen content, electro-conductivity, water depth, turbidity and number of other organisms and the paddy rice height, density, number of tillers. Semi-structured questionnaires were administered to 192 randomly selected farmers to establish the effect of malaria on rice yield. Results indicated presence of significant numbers anopheles mosquito larvae in straws, side ditches, worm holes, weeds, tyre print, tilled land,hoof print, and paths at (p<0.05). Pearson correlations results between variables and anopheles larvae dip-1 were 0.17, 0.437, 0.193, -0.357, -0.393, -0.329, 0.356, and -0.329 for water depth, turbidity, temperature, paddy density, paddy height, oxygen content, electro-conductivity and number of rice tillers respectively, significant at p<0.05. Stepwise regression analysis indicated that turbidity, water electro-conductivity, rice height, water depth, water temperature, number of other organisms and rice density, significantly (p<0.05) explained the number of anopheles mosquitoes in a given habitat. Results also indicated that malaria significantly affected the farmers' expected paddy rice yield; reducing it by 52%from 2,480 to 1,170 kg/ha season-1 (p<0.05). Labour requirement results indicated that nursery preparation, land preparation, transplanting, weeding, bird scaring and harvesting required 5.53,141.65, 101.12, 99.36, 30.25 and 78.0 person days/ha respectively. Sensitivity results indicated that labour loss during nursery preparation, land preparation, transplanting, weed control, bird scaring and harvesting led to a yield loss of 45, 24.6, 63.3, 42.4, 104.6 and 43.5 kg/ha person/day respectively. This research is fundamental in guiding malaria vector source control in paddy rice growing systems in Uganda and Sub-Saharan Africa as a whole.