Spatiotemporal Mapping of Annual Malaria Incidence in Rivers State, Nigeria

Abstract

Rivers State is the centre of Nigeria's oil industry and has the presence of oil prospectors including expatriates who are at risk of malaria infection.  Periodic analysis of epidemiological data will enable malaria control programmers to appraise the interventions carried out over the years and assist in  the development of sustainable and adaptive strategies directed from an informed local level. This study, therefore, examined spatiotemporal variations  in malaria incidence in the State using Annual Parasite Incidence (API) as an indicator. Monthly reported malaria cases from 2007-2017 at the local  government area (LGA) level were retrieved from the Integrated Disease Surveillance Response (IDSR) system of Rivers State Ministry of Health while  projected population data for the same period were obtained from the National Bureau of Statistics. API of the LGAs from 2007 to 2017 were computed,  integrated into GIS, and subjected to weighted overlay analysis to delineate the risk zones. The eleven-year retrospective study of malaria in Rivers State  displayed geographical variations which were statistically significant between the LGAs. Malaria incidence fluctuated throughout the study period. API  values increased from 13.746 in 2007 to 34.067 in 2013 and dropped to 8.721 in 2017. All the LGAs recorded API values below 100, indicating a very low  malaria burden in a controlled setting. However, none of the LGAs has reached the WHO standard level for the elimination of transmission. Ikwerre,  Eleme, Ogu-Bolo and Opobo/Nkoro LGAs were assigned to the very high malaria risk stratum (362.615 to 490.005) whereas Abua-Odual, Akuku-Toru and  Degema LGAs were assigned to very low-risk malaria stratum (103.281 to 113.897). The findings of this research will aid stakeholders in evaluating the  impact of control strategies employed over the years and possibly, revisit malaria extant interventions for improved malaria control outcomes.