Browsing by Author "Ngenokesho, Padelia N."

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    Incedence of Malaria in relation to residual efficacy of 2017 indoor residual spraying during 2018 Malaria season in Engela district, Ohangwena, Namibia
    (University of Namibia, 2020) Ngenokesho, Padelia N.
    ntroduction: Malaria remains a public health problem in Africa and other countries of subtropical. In 2017, an estimated 219 million cases of malaria occurred worldwide (95% confidence interval [CI]: 203–262 million), compared with 215 million malaria cases in 2016. Most malaria cases in 2017 were in the WHO African Region (200 million or 92%), followed by the WHO South-East Asia Region with 5% of the cases and the WHO Eastern Mediterranean Region with 2%. In 2017, there were an estimated 435 000 deaths from malaria globally, compared with 451 000 estimated deaths in 2016. In 2017, Namibia recorded high number; (66141 (27.3%) of malaria cases as compared to 2016 (24869 (10.3%) and 2018 (36451(14.8%). Primary malaria prevention on a large scale depends on two vector control interventions which are indoor residual spraying (IRS) and insecticide treated mosquito nets (ITNs). In 2017, Engela district, Ohangwena region used only Deltamethrin in both structures because of unavailability of DDT at the moment of spraying season. The duration of Deltamethrin effectiveness (residual efficacy) is 6 months as per WHO guideline. Therefore, the researchers determined the residual efficacy of insecticide (Deltamethrin) used in 2017 Indoor residual Spraying program in relation to incidence of malaria in Engela district, Ohangwena region. Methods: The researchers conducted an analytic quantitative cross sectional study to determine the residual efficacy of insecticide used in 2017 Indoor residual Spraying program in relation to incidence of malaria in Engela district, Ohangwena region. Malaria line list for 2018 was used to identify the villages affected by Malaria. The researchers collected mosquito larva for wild mosquitoes at mosquito breeding sites around Engela district and grew them into adult mosquitoes at the Oshakati Insectary laboratory. Wild common malaria vectors, which were unfed adult female anopheles’ mosquitoes were transported in the cage to the field at the time of testing. The WHO bioassays cone was used during testing of Deltamethrin residual efficacy which was used for both traditional (rough) and modern (smooth) sprayed walls. Four cones (high, middle and low surface level) per surface with twenty mosquitoes per cone were used. Three cones were experimental cones and one was control cone per structure. The study was done during 2018 malaria season after five and six months (April to May 2018) from 2017 IRS to find out the residual efficacy of 2017 IRS insecticide used. Bi-variate analysis was calculated to determine the statistical significant between mortality rate and types of the walls as well as time interval. Statistical significant was calculated at P-value < 0.05 and odds ratios at Confident Interval (CI) 95% confidence level to determine significant associations. Results: The district recorded 460 malaria cases from January –July 2018, of which 65 (14%) were local transmission and did not travel outside the district for about one incubation period (2-14 days) before the onset of symptoms. The peak months were March (23%), April (26%) and May (25%). The district had the total of 376 villages of which 156 (41%) were managed to be sprayed in 2017 and 220(59%) were not sprayed. Malaria local transmission cases were reported in 44 (10%) villages; of which 30/44 (68%) villages received IRS while 14/44 (32%); Odd ratio=3.8 CI 1.9-7.5; P value=0.0006). Only villages reported cases in the last 3 years were part of spraying campaign. In 2017, Engela district, Ohangwena region used only Deltamethrin in both structures because of unavailability of DDT during spraying season. Residual efficacy was tested in 23 malaria affected villages and on 50 sprayed structures. The time interval was one month, five to six-month time interval between IRS and testing of residual efficacy. The overall mortality rate (residual efficacy) was 46%. There is statistically significant between mortality rate and traditional structures with OR 1.66 CI 1.42-1.95 (P0.001), painted modern structures OR 0.77 CI 0.65 – 0.91 (P 0.002), time interval with OR 0.35 (0.29 – 0.41) P 0.001 and high position of the cone on the wall OR 0.76 CI 0.65 -0.88 (P 0.001). Conclusion: In conclusion, it is worth noting that villages that were sprayed during 2017 IRS program recorded many cases as compared to non-sprayed villages and it were found to be significant. This can be influenced by areas with source of infection, travelling, evening activities, and age. The effectiveness (residual efficacy) of 2017 IRS during malaria peak months was 46% and it was found that it was direct proportional with time interval. Therefore, the researchers recommended active case detection team to consider other control intervention such as use of Long Lasting Insecticide Treated Nets, increase community malaria awareness and early seeking of treatment, early contact tracing of malaria cases to cut-of the infection and behavioral community change.