Assessment of the Persistence of Malaria To Control Measures in Dembia District, Northwestern Ethiopia: A Retrospective and Longitudinal Prospective Study

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Addis Ababa University


Despite more than six decades of continued control effort, malaria remains a major public health problem in Dembia District. In order to determine the causes for the persistence of malaria to the control measures, retrospective and longitudinal prospective studies were conducted in the District. A retrospective data on monthly malaria incidence, malaria control interventions and meteorological variables were collected for the period 2001 to 2015. For the prospective parasitological surveys, all consenting family members selected randomly from four rural Kebeles were examined for the presence of malaria parasites following standard parasitological procedures. Knowledge, attitude and practice survey was conducted in parallel with parasitological surveys. Adult and larval mosquito surveys were undertaken in four selected Kebeles following standard entomological methods. Adult mosquitoes were collected indoors and outdoors and identified into species morphologically based on keys; their host preference and sporozoite infection rates were determined by enzyme linked immuno sorbent assay. The identification of Anopheles arabiensis was confirmed by polymerase chain reactions. In spite of increased indoor residual spraying coverge, retrospective data showed high malaria incidence in most years, except a sharp decline in 2006, 2007, 2008 and 2014. The incidence of monthly total malaria due to Plasmodium falciparum significantly (P<0.05) correlated with rainfall at one to four months lag. In the six month prospective parasitological surveys, a total of 4568 samples were examined microscopically. This showed an average of 7.4% positivity for malaria, of which 74.3% were due to P. falciparum and 20.4% P. vivax, whereas the remaining 4.4% and 0.9% were P. falciparum/P. vivax co-infections and P. ovale, respectively. Lack of consistency in indoor residual spraying practice in lower altitude Kebeles and not including malarious mid-altitude Kebeles in indoor residual spraying program explain the highest malaria incidence ii observed in the major malaria transmsion season (Sepember-December) in the reterospective and prospective studies. The prevalence of Plasmodium falciparum infections during the dry season appears to be the consequence of river edge pools created mainly by irrigation activities. The study also provided evidence that frequent population movements in and out of malarious areas in the region and outdoor human activities at night are common features that would impede the efficiency of malaria control measures. In addition, poor utilization of long lasting insecticidal net was determined as a factor contributing to the persistence of malaria in the region. The detection of one Plasmodium falciparum infected Anopheles arabiensis from outdoor collection in a sprayed (September) low altitude Kebele is an indication that outdoor transmsion may be taking place. This is another possible reason for the ineffective malaria control. One evidence for the wrong timing of indoor residual spraying operations for malaria control in the District was 50% P. falciparum sprozoite infected An. arabiensis collected during the wet season (June and August 2015). Therefore, the failure to target May to August malaria transmsion season by the malaria control activities as well as the disregard for malaria control in the mid-altitude localities appear to be the main weaknesses of the malaria control program in the District. In addition, increasing human outdoor activities which will expose them to the outdoor biting and resting behavior of Anopheles arabiensis, population movement and irrigation activities are important contributors for the persistence of malaria in Dembia District.



Dembia, Malaria Persistence, Malaria Incidence, Malaria Control Interventions, Meteorological Variables, Population Movment, Sprozoite Rate