The phenomenon of diminishing –returns in the use of bed nets and indoor house spraying and the emerging place of antimalarial medicines in the control of malaria in Uganda

Background: The mosquito net existed long before it was known that mosquitoes transmitted malaria. Therefore it was not intended for malaria control. Objectives: To scrutinise the patterns of prevalence and identify any hitherto unknown factors that could explain the findings. Methods: Retrieval of records on malaria prevalence. Findings: Households sprayed in the previous 12 months or owning at least one ITN: 77.8% and IRS: 31.6% in mid-northern districts. Paradoxically, this was the highest malaria prevalence at 80.1%, hence the phenomenon of diminishing-returns. The urban children (28.6%), those of post-secondary education mothers (14.3%) and in the highest wealth quintile (33.3%) had a lower malaria prevalence than those without education (55.8%) and the less wealthy (67.6%), (p 0.001). In all, the connection was that the urban (77.4%) and the wealthy (63.8%) sought health care first from hospitals, for proper treatment. Hence the low prevalence is most likely to be due to anti-malarial medicines and not to bed-nets and IRS, since the other findings of the survey show that there are no significant differences in bed nets ownership and usage and IRS in both groups. Recommendation: Antimalarial medicines should therefore be used to control malaria instead of the nets and IRS.