Abstract
BackgroundMalaria control remains a significant challenge in the Solomon Islands. Despite progress made by local malaria control agencies over the past decade, case rates remain high in some areas of the country. Studies from around the world have confirmed important links between climate and malaria transmission. This study focuses on understanding the links between malaria and climate in Guadalcanal, Solomon Islands, with a view towards developing a climate-based monitoring and early warning for periods of enhanced malaria transmission.MethodsClimate records were sourced from the Solomon Islands meteorological service (SIMS) and historical malaria case records were sourced from the National Vector-Borne Disease Control Programme (NVBDCP). A declining trend in malaria cases over the last decade associated with improved malaria control was adjusted for. A stepwise regression was performed between climate variables and climate-associated malaria transmission (CMT) at different lag intervals to determine where significant relationships existed. The suitability of these results for use in a three-tiered categorical warning system was then assessed using a Mann–Whitney U test.ResultsOf the climate variables considered, only rainfall had a consistently significant relationship with malaria in North Guadalcanal. Optimal lag intervals were determined for prediction using R2 skill scores. A highly significant negative correlation (R = − 0.86, R2 = 0.74, p < 0.05, n = 14) was found between October and December rainfall at Honiara and CMT in northern Guadalcanal for the subsequent January–June. This indicates that drier October–December periods are followed by higher malaria transmission periods in January–June. Cross-validation emphasized the suitability of this relationship for forecasting purposes {text{R}}^{2}{_{text{LOOCV}}} = 0. 6 3 as did Mann–Whitney U test results showing that rainfall below or above specific thresholds was significantly associated with above or below normal malaria transmission, respectively.ConclusionThis study demonstrated that rainfall provides the best predictor of malaria transmission in North Guadalcanal. This relationship is thought to be underpinned by the unique hydrological conditions in northern Guadalcanal which allow sandbars to form across the mouths of estuaries which act to develop or increase stagnant brackish marshes in low rainfall periods. These are ideal habitats for the main mosquito vector, Anopheles farauti. High rainfall accumulations result in the flushing of these habitats, reducing their viability. The results of this study are now being used as the basis of a malaria early warning system which has been jointly implemented by the SIMS, NVBDCP and the Australian Bureau of Meteorology.
Highlights
Malaria control remains a significant challenge in the Solomon Islands
seasonal climate outlooks in Pacific Island countries” (SCOPIC) showed that the predictability of malaria incidence based on climate variables in the first half of the year was significantly better than in the second half, where little predictability existed
This study attempts to quantify the relationship between climate and malaria in Guadalcanal on an inter-annual timescale
Summary
Malaria control remains a significant challenge in the Solomon Islands. This study focuses on understanding the links between malaria and climate in Guadalcanal, Solomon Islands, with a view towards developing a climate-based monitoring and early warning for periods of enhanced malaria transmission. There has been a renewed major focus on malaria eradication at the edges of this region to effectively shrink the worldwide malaria endemic region [1,2,3,4]. Under this strategy, the countries of the western Pacific, including the Solomon Islands and Vanuatu have become an obvious target for malaria elimination. With the precise composition of these programmes and their associated funding allocations decided at the provincial level, there was substantial variation in the effectiveness of control practices across the country
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