Impact of insecticide treated nets and indoor residual spraying on malaria case prevalence in Geita and Nyang’hwale districts of Tanzania.

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Kiputa, Thobias Gaudenxce
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The University of Zambia
A retrospective longitudinal study was conducted to assess the impact on malaria prevalence of ITNs combined with IRS in Geita district, IRS alone in Nyang’hwale district and to compare the two interventions between the two districts. Malaria is a protozoan disease and one of the leading causes of illness and deaths in the world. Infection occurs after exposure to blood-feeding infective Anopholes mosquitoes. Malaria is predominant in the tropics and subtropics and it is reported that malaria kills a child every minute. In Tanzania, at least 40% of outpatient attendances are attributable to malaria. Geita and Nyang’hale districts are within Geita region where malaria prevalence is highest in Tanzania. Geita and Nyang’hwale districts of Tanzania have been controlling malaria transmission by using the combined intervention of insecticide-treated nets (ITNs) with indoor residual spraying (IRS) and IRS alone respectively. District malaria surveillance data for five years (2011-2015) and two years (2013-2014) were collected and analyzed for Geita and Nyang’hwale districts, respectively. Results show that a total of 1,387,805 ITNs were distributed and 435,719 households sprayed between 2011 and 2015, however IRS coverage was uneven. There was evidence of malaria prevalence reduction, from 53% to 12%, in Geita district within the five years of intervention. The ITNs coverage was associated with a reduction in malaria prevalence while IRS was not. In Nyang’hwale district malaria cases increased from 103,788 cases in 2013 to 123,337 in 2014, and were accompanied by decreased households spraying from 49,554 to 41,632. The combined intervention reduced malaria prevalence in Geita district while an increase in malaria cases was observed in Nyang’hwale district where IRS alone was applied. Malaria prevalence difference between ITNs combined with IRS intervention and IRS intervention alone was 0.09 and prevalence ratio was 0.73. Only ITNs had a significant effect on malaria cases reduction (p<0.001). However, even at 100% ITN coverage, the estimated probability of finding malaria cases was not zero. Therefore, based on this study, it can be concluded that ITNs were responsible for the observed reduction in malaria prevalence in the combined use of ITNs and IRS that both use pyrethroid insecticides under the prevailing field conditions in Geita district. The use of IRS either in the combined intervention in Geita district or alone in Nyang’hwale district had insignificant effects on malaria control.
Malaria--Tanzania , Malaria--Immunological aspects--Tanzania