Abstract
Since the 1970s, the northern part of Côte d'Ivoire has experienced considerable fluctuation in its meteorology including a general decrease of rainfall and increase of temperature from 1970 to 2000, a slight increase of rainfall since 2000, a severe drought in 2004–2005 and flooding in 2006–2007. Such changing climate patterns might affect the transmission of malaria. The purpose of this study was to analyze climate and environmental parameters associated with malaria transmission in Korhogo, a city in northern Côte d’Ivoire. All data were collected over a 10-year period (2004–2013). Rainfall, temperature and Normalized Difference Vegetation Index (NDVI) were the climate and environmental variables considered. Association between these variables and clinical malaria data was determined, using negative binomial regression models. From 2004 to 2013, there was an increase in the annual average precipitation (1100.3–1376.5 mm) and the average temperature (27.2°C—27.5°C). The NDVI decreased from 0.42 to 0.40. We observed a strong seasonality in these climatic variables, which resembled the seasonality in clinical malaria. An incremental increase of 10 mm of monthly precipitation was, on average, associated with a 1% (95% Confidence interval (CI): 0.7 to 1.2%) and a 1.2% (95% CI: 0.9 to 1.5%) increase in the number of clinical malaria episodes one and two months later respectively. A 1°C increase in average monthly temperature was, on average, associated with a decline of a 3.5% (95% CI: 0.1 to 6.7%) in clinical malaria episodes. A 0.1 unit increase in monthly NDVI was associated with a 7.3% (95% CI: 0.8 to 14.1%) increase in the monthly malaria count. There was a similar increase for the preceding-month lag (6.7% (95% CI: 2.3% to 11.2%)). The study results can be used to establish a malaria early warning system in Korhogo to prepare for outbreaks of malaria, which would increase community resilience no matter the magnitude and pattern of climate change.
Highlights
Malaria is a mosquito-borne infectious disease caused by parasitic protozoa of the genus Plasmodium that is transmitted by female Anopheles mosquitoes
90% of all malaria deaths occur in sub-Saharan Africa and most of them are in children under 5 years old [3].This is because the most effective malaria vector (i.e Anopheles gambiae) is the most widespread in Africa and the most difficult to control [4]
We modeled the expected value E(Y) of monthly malaria case counts Y by health center as an exponential function of a linear predictor defined by the scalar product of a column vector X of independent variables and a row vector β of associated regression coefficients, i.e., EðYÞ 1⁄4 expðbXÞ
Summary
Malaria is a mosquito-borne infectious disease caused by parasitic protozoa of the genus Plasmodium that is transmitted by female Anopheles mosquitoes. The efforts of the international community over the past 15 years have reduced malaria risk levels by 40% from 2000 to 2015, and large regions of Africa are in a position to consider elimination strategies [2]. Despite this progress, about 3.2 billion people remain at risk of malaria in 2015 [3]. Malaria’s geographic range, seasonal pattern, and/or intensity of transmission are influenced by social and ecological systems and any change is likely to affect the epidemiology of malaria [1, 5,6,7]. Because of the association between weather and climate patterns, temperature, precipitation, and extreme events, and malaria, climate change is expected to affect the distribution and seasonal activity of Anopheles mosquitoes, assuming no change in malaria control programs [8, 9]
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