Are We Ready For A Longer Mosquito Season From Climate Change?

Are We Ready For A Longer Mosquito Season From Climate Change?
Climate change affects the social and environmental determinants of health. With each passing year, we are reminded of how the increasing frequency and severity of extreme weather events are becoming the new normal. There are clear indications that climate change has direct and indirect adverse impacts on human health. Environmental health exposures, such as high temperatures or extreme weather events, amongst others, are putting large portions of the global population at risk of various negative health effects. The World Health Organisation (WHO) predicts that between 2030 and 2050, climate change will cause approximately 250,000 additional deaths worldwide each year.

We are well aware by now of the many ways in which climate change is reshaping the world we live in, but how are vector biologists experiencing these changes? As a mosquito-control professional, I have the luxury of closely observing mosquito populations in a specific area over a long period and can pick up on trends and changes. A lot of interesting current research sheds light on the relationship between climate change and mosquitoes. Studies have linked drought and rising temperatures to increased incidence of arthropod-vectored disease and a longer mosquito season.

The WHO predicts that countries with a fragmented health infrastructure are among the least able to cope with climate change health impacts when no assistance to prepare and respond will be provided. Extreme events, including heat and flooding, promote the spread of vector-borne diseases, transmitted by vectors such as mosquitos, ticks, and fleas. Increased temperature increases vector and pathogen metabolism, thus allowing for faster replication and spread, whereas erratic rainfall patterns may increase the availability of suitable breeding sites. These trends may expand the transmission season in tropical and sub-tropical areas. It also poses a risk of the establishment of invasive vector species and infectious diseases in temperate climates by making the environment more conducive for the proliferation of the vectors, a trend that could also be observed in some areas of Pakistan.

With increasing climate change, climate-sensitive infectious diseases, particularly mosquito-borne diseases, are on the rise. According to recent reports, 2019 has been an exceptionally active year of dengue fever outbreaks worldwide. In the case of Pakistan, there has been a significant increase in the incidence and severity of mosquito-borne disease outbreaks in recent past, calling for a better understanding of how climate change is shaping the future burden of mosquito-borne diseases in highly susceptible areas. As outlined, with increasing climate change and international mobility, such trends may become more likely, with prolonged transmission seasons, whereas invasive vector species and newly emerging viruses may infest and establish in yet non-affected but increasingly suitable areas. Addressing the health challenges of mosquito-borne epidemics is hence one important element in the quest for greater climate resilience.

As a mosquito control professional, I am often asked by friends and acquaintances to predict the upcoming mosquito season. This is never easy to do because mosquitoes are so weather dependent in very complex ways. At this stage, using historical and current mosquito population data, along with weather data, is an important part of the integrated vector management toolbox. The country’s metrological department is capable of predicting how much rainfall and/or flooding could happen in a year. There is an urgent need to establish a real-time data sharing mechanism among relevant departments. It can help most control experts in organising proactive activities for managing populations rather than reactive ones. The teams on the ground can plan beforehand to treat these future floodplains and/or high-risk areas for larvae as time, resources, and weather allows, hopefully reducing the need to resort to area-wide adulticiding. It will be interesting to see what the 2022 mosquito season brings.

The author is Assistant Professor at the Department of Medical Entomology and Parasitology at the Institute of Public Health, Lahore