Scientists: Climate change is attracting more disease-carrying insects to the UK, but don’t panic

Roz Pidcock

Disease-carrying insects are finding new places to call home, according to new research. A Royal Society special issue finds that as the climate warms, traditionally tropical insects are spreading to more temperate regions, including the UK and Europe.

The UK could play host to a black and white-striped insect known as the Asian Tiger Mosquito by the middle of the century, one paper finds.

As The Times reported today:

“Yellow fever and dengue threaten to reach Britain as climate change makes the country more hospitable to a mosquito that carries an arsenal of exotic diseases, a study warns.”

But it’s important not to overreact, the scientists involved tell Carbon Brief. While new health risks need careful monitoring, a public-health emergency isn’t on the cards in the UK.

New, unfamiliar territory

Disease-carrying insects, such as mosquitoes and ticks, respond very quickly to changes in their surroundings. Dr Paul Parham, expert in health and public policy at the University of Liverpool and organiser of the special issue, explains:

“The behaviour of disease vectors, such as mosquitoes, is known to be very sensitive to temperature and rainfall, for example, so it seems unquestionable that climate change will affect many, if not all, of these diseases.”

As new habitat becomes suitable and the insects expand their geographical ranges, scientists expect the UK could be exposed to new diseases. Parham tells Carbon Brief:

“Based on the latest modelling studies … it appears that the UK (and other areas of northern Europe) will become slightly more suitable for one of the key vectors of dengue and chikungunya, possibly by up to around 20 per cent over the next few decades.”
Image - Map showing habitat suitability for the Asian Tiger mosquito expressed as the increase between 2000-2009 and 2045-2054 (note)

Habitat suitability for the Asian Tiger mosquito expressed as the increase between 2000-2009 and 2045-2054 (a) North America and (b) Europe. Source: Proestos et al. (2015).

Southern parts of the UK already offer a suitable habitat for the Asian Tiger Mosquito, which scientists expect to increase in the next 35 years as temperatures rise. The Times says:

“Some scientists are now concerned that southern England could become a “hot spot” for the insect and the viruses it carries, although others said it was not yet clear whether it could thrive on this side of the Channel.”

While the potential impact on human health is arguably one of most important effects of climate change, predicting the scale of the risk in a given place is difficult, says Parham.

So, how worried should we be?

A complex set of causes

Many factors other than temperature affect the spread of disease, Yiannis Proestos, researcher at the Cyprus Institute and lead author on the Asian Tiger Mosquito paper, tells Carbon Brief:

“For instance, socioeconomic status, population movement and globalization, [are] all important factors that may have profound consequences in the spreading of vectors and, more generally, of diseases, have not been taken into account in this study.”

So, while climate change might govern the global distribution of a disease, other factors will determine the magnitude and extent of an outbreak. This means making predictions based on how temperatures are expected to change is far from straightforward, Parham explains:

“[A]n increase in the suitability of the UK to certain disease vectors certainly does not imply an increase in disease risk.”

Added difficulty comes from uncertainty in climate projections, particularly at regional and local scales that scientists need to determine how quickly a disease might spread, Parham says.

The insects themselves could change how effectively they carry disease, Dr Nina Fefferman from Rutgers University, lead author on another of the special issue papers, tells Carbon Brief. She says the mosquitoes’ DNA can evolve faster than scientists previously thought when the climate in their habitat changes:

“If vectors are evolving rapidly in response to changing conditions in their current habitats, they may incidentally change their ability to carry the disease among hosts (getting either worse or better).”
Image - A blacklegged tick (note)

Other papers in the special issue focus on blacklegged ticks, the cause of Lyme disease in Northeastern North America “The Wood Tick”. Credit: Shutterstock.

A nuanced debate

The uncertainty around projections means there needs to be a bit more subtlety when talking about disease and climate change, says Prof Andrew Townsend Peterson, a specialist in ecology and evolutionary biology at the University of Kansas and co-author of one of the special issue papers on the global distribution of mosquitoes. He tells Carbon Brief:

“Yes, there will be changes that are driven by mosquito vectors responding to climate, but they will not be huge epidemics that arrive the day after tomorrow. Rather, they will be trends in abundance or intensity, and they will open new opportunities for spread of disease.”

The latest report from the Intergovernmental Panel on Climate Change says local changes in temperature and rainfall have altered the distribution of some disease vectors. But it adds that at present, the worldwide burden of human ill-health from climate change is relatively small compared with effects of other stressors, and is not well quantified.

Gradual shifts and invasions of vectors into new areas will have implications for public health, but as long as some basic precautions are taken at harbours and airports, for example, there’s no need to panic about the Asian Tiger Mosquito in the UK, says Proestos.

On a global scale, there’s a lot to be gained by being more proactive when it comes to emerging health risks, says Parham:

“Humanity has tended to react to emerging diseases as they occur. We should perhaps be more proactive and use the past to help us anticipate the future. [P]roactive risk management is less expensive, and thus more effective, than responding after the crisis.”

The study of vector-borne diseases is a rapidly developing field, but many challenges remain. The research published in this special issue of papers is vital for developing better public health policies based on the latest evidence, Parham concludes.

“Whether you like it or not, climate change is happening and deaths from vector-borne diseases due to climate change are inevitable and unavoidable – doing nothing is not an option.”
Main image: Mosquitos on human skin at sunset.

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