Mayilsamy Muniaraj, Veeramanoharan Rajamannar, Jain Kamala, Balakrishnan Vijayakumar, Rajaiah Paramasivan
ICMR-Vector Control Research Centre Field Station, No. 4, Sarojini Street, Chinna Chokkikulam, Madurai 625 002, Tamil Nadu, India.
Department of Biotechnology, Madha Enginerring College, Chennai 600 069, Tamil Nadu, India.
Trop Med Infect Dis. 2024 Dec 19;9(12):309. doi: 10.3390/tropicalmed9120309.
Malaria remains a significant public health problem in India. Although temperature influences Anopheline mosquito feeding intervals, population density, and longevity, the reproductive potential of the Plasmodium parasite and rainfall influence the availability of larval habitats, and evidence to correlate the impact of climatic factors on the incidence of malaria is sparse. Understanding the influence of climatic factors on malaria transmission will help us predict the future spread and intensification of the disease. The present study aimed to determine the impact of temporal trend of climatic factors such as annual average maximum, minimum, mean temperature, and rainfall on the annual incidence of malaria cases in India for a period of 61 years from 1961 to 2021 and relative humidity for a period of 41 years from 1981 to 2021. Two different analyses were performed. In the first analysis, the annual incidence of malaria and meteorological parameters such as annual maximum, minimum, and mean temperature, annual rainfall, and relative humidity were plotted separately in the graph to see if the temporal trend of climatic factors had any coherence or influence over the annual incidence of malaria cases. In the second analysis, a scatter plot was used to determine the relationship of the incidence of malaria in response to associated climatic factors. The incidence of malaria per million population was also calculated. In the first analysis, the annual malaria cases showed a negative correlation of varying degrees with relative humidity, minimum, maximum, and mean temperature, except rainfall, which showed a positive correlation. In the second analysis, the scatter plot showed that the rainfall had a positive correlation with malaria cases, and the rest of the climatic factors, such as temperature and humidity, had negative correlations of varying degrees. Out of the total 61 years studied, in 29 years, malaria cases increased more than 1000 square root counts when the minimum temperature was at 18-19 °C; counts also increased over a period of 33 years when the maximum temperature was 30-31 °C, over 37 years when the mean temperature was 24-25 °C, over 20 years when the rainfall was in the range of 100-120, and over a period of 29 years when the relative humidity was at 55-65%. While the rainfall showed a strong positive correlation with the annual incidence of malaria cases, the temperature and relative humidity showed negative correlations of various degrees. The increasing temperature may push the boundaries of malaria towards higher altitude and northern sub-tropical areas from the southern peninsular region. Although scanty rainfall reduces the transmission, increases in the same would increase the malaria incidence in India.
疟疾在印度仍然是一个重大的公共卫生问题。尽管温度会影响按蚊的进食间隔、种群密度和寿命，疟原虫的繁殖潜力以及降雨会影响幼虫栖息地的可用性，但关于气候因素对疟疾发病率影响的相关证据却很少。了解气候因素对疟疾传播的影响将有助于我们预测该疾病未来的传播和加剧情况。本研究旨在确定1961年至2021年61年间，诸如年平均最高、最低、平均温度和降雨量等气候因素的时间趋势，以及1981年至2021年41年间相对湿度对印度疟疾病例年发病率的影响。进行了两种不同的分析。在第一次分析中，分别在图表中绘制疟疾病例年发病率和气象参数，如年最高、最低和平均温度、年降雨量以及相对湿度，以查看气候因素的时间趋势是否与疟疾病例年发病率具有任何一致性或影响。在第二次分析中，使用散点图来确定疟疾病例发病率与相关气候因素之间的关系。还计算了每百万人口的疟疾病例发病率。在第一次分析中，除降雨量呈正相关外，疟疾病例年发病率与相对湿度、最低、最高和平均温度呈不同程度的负相关。在第二次分析中，散点图显示降雨量与疟疾病例呈正相关，而其余气候因素，如温度和湿度，呈不同程度的负相关。在研究的61年中，有29年当最低温度为18 - 19°C时，疟疾病例增加超过1000平方根计数；当最高温度为30 - 31°C时，在33年期间计数也增加；当平均温度为24 - 25°C时，在37年期间增加；当降雨量在100 - 120范围内时，在20年期间增加；当相对湿度为55 - 65%时，在29年期间增加。虽然降雨量与疟疾病例年发病率呈强正相关，但温度和相对湿度呈不同程度的负相关。温度升高可能会将疟疾的边界从南部半岛地区推向更高海拔和北亚热带地区。虽然降雨稀少会减少传播，但降雨量增加会增加印度的疟疾发病率。
