Mosquitoes on accumulated rainwater in Chandigarh. (Express Photo by Jasbir Malhi)
THE LINK between changing weather patterns on account of climate change and the spread of diseases is still being studied and understood. The Intergovernmental Panel on Climate Change (IPCC) had predicted that warming due to climate change could lead to longer transmission seasons for malaria and dengue.
Also, rain and humidity are enablers for both diseases as they assist in the hatching of young mosquitoes and the survival of adult mosquitoes. Higher temperatures over longer periods are extending the transmission time for both dengue and malaria.
A study conducted by the Chandigarh health and weather department using data from 2000 to 2015 has also confirmed the co-relation between the climate and the chief vector-borne disease in the city, malaria. “In our analysis so far, we have found that malaria is co-related with rainfall in the city,” says Dr Gaurav Aggarwal, UT’s anti-malaria officer, who was part of the study.
During the study, it was found that the monthly mean maximum and minimum temperatures and monthly amount of rainfall were positively correlated with the monthly cases of malaria. In Chandigarh, the study found that the peak seasons of malaria were monsoon (June-September) and post monsoon (October-December). As per the health data, Chandigarh recorded 150 malaria cases in 2013; 114 in 2014; 152 in 2015; and 157 in 2016. This year, the city has had 36 cases of malaria so far.
Significantly, the overall decline in rainfall since 2012 has not led to a decline in the incidence of malaria. In fact, the incidence has only increased over the years, perhaps because of the extended post-monsoon period, and the delay in the arrival of winter.
“Over the years the rainfall in the city has recorded a decline and the rainfall pattern has changed to intermittent rainfall. This leads to stagnation of water. This situation leads to early conversion of larvae into an adult mosquito,” says Dr Gaurav. “Another reason is that the vector has adapted itself to the climatic change and vector-borne diseases are no more seasonal. They sustain even at extreme high temperature and now the cases can be seen throughout the year.”
While the study has found that malaria cases are negligible between March-May and January-December, there is incidence in all other months, and the incidence of other vector diseases like malaria and chikungunya has also been increasing. The study report lists other factors, such as change in land use patterns and construction of water storage devices due to reduced availability of water, positively correlating with malaria transmission.
Dr Aggarwal says more studies need to be done to come up with many strategies that can eradicate the malaria in Chandigarh. “We have already chalked out a strategy to bring down the number of malaria cases in the city, but studies like this one will help us understand the transmission of disease further.”
He says study will not be restricted to malaria alone. “We have started to access the importance of environment and climate on vectors in Chandigarh. We will do the same pattern of analysis for chikungunya, swine flu and dengue. Once we come up with analysis, it will help get an idea about the possible spread of these diseases, so that we can take steps beforehand,” says Aggarwal.
