Climate Change And How It Is Giving Rise To Vector-Borne Diseases

One of the most serious consequences of climate change is the profound impact on human health and wellbeing. Almost every element of climate change affects populations across the world – be it deforestation, melting glaciers, extreme climate events or pollution.

But it is the rise in global temperatures that is most worrying. Apart from the known and visible effects of rising heat, like exhaustion and heat stroke, an almost invisible-till-you-think-about-it change is being seen in the spread of vector-borne diseases.

Vector-borne diseases are diseases transmitted to humans and animals through the bite of infected arthropods, such as mosquitoes, ticks, and flies. The relationship between climate change and vector-borne diseases is complex and multifactorial, involving various environmental, ecological, and socio-economic factors. Let’s explore how climate change is driving the increase in vector-borne diseases and what mechanisms are aiding this.

One of the primary ways in which climate change is contributing to the rise of vector-borne diseases is by influencing the distribution and abundance of vectors through rising temperatures and precipitation patterns.

Rising temperatures across the planet are changing the geographic distribution of vectors. With this rise in temperature, vectors are now being found to survive and thrive in places with higher latitude and altitude which were not conducive to vector survival, breeding and disease transmission. Let’s consider the example of tick-borne encephalitis virus (TBEV) that has recently been reported to infect hikers in the United Kingdom. Such reports were rare earlier but now could be a result of the rise in temperatures (last winter was one of the warmest ever in Europe).

Even mosquitoes that transmit diseases such as dengue fever, zika virus, and chikungunya are moving into new geographies causing the emergence of these diseases in previously unaffected regions. Other diseases like Lyme’s disease and West Nile virus disease are being found in newer regions.

The change in rainfall patterns are also a source of concern. With more frequent and intense rainfall events, occurring in months when rain is not expected there is a creation of new breeding sites for vectors and existing breeding sites are expanding – the stagnant water provides ideal conditions for vectors like mosquitoes to reproduce. Even in areas with drought conditions, where water availability poses a challenge, humans are creating options for water storage and modifying usage practices – something that can increase exposure to vector-borne diseases

The vectors themselves are undergoing changes in their lifecycles and in the way they behave. Warmer temperatures are accelerating the reproduction and development of vectors, leading to increased rates of vector populations. The feeding behaviour of vectors is also undergoing modification in frequency of feeding and thereby reduction in the time it takes for pathogens to replicate within the vector. This increases the probability of transmission to a host.

It is well known that vectors depend upon hosts for survival. And climate changes is also impacting these hosts. With an increasing density of hosts such as birds, rodents and other mammals, (as land is lost to forest fires and droughts) blood meals for vectors become more easily available and impact vectors’ ability to reproduce and transmit diseases. This change in host-vector-pathogen interaction is also altering the dynamics of disease transmission.

Changes in climate are impacting human as well, modifying migration and settlement pattern. Displaced populations may not be able to access basic necessities like clean water, sanitation, and healthcare and become vulnerable to vector-borne diseases.

Vector-borne diseases remain a major public health concern, causing significant morbidity and mortality worldwide. These diseases disproportionately affect vulnerable populations, including the poor, children, and marginalized communities, who may have limited access to healthcare and resources for prevention and control. International SOS is working with large corporations to provide an early warning system on vector-borne diseases and helping them to develop strategies that mitigate the increasing risks of these diseases globally.