Climate change could result in the spread of tropical diseases such as malaria, dengue, Lyme disease and yellow fever, according to a leading disease ecologist.
Speaking today to mark the World Health Organisation’s World Health Day, Durham University School of Biological and Biomedical Sciences Professor Steve Lindsay said that everyone from government and health organisations to individuals needed to be “alert” to the possibility that disease-carrying insects, known as vectors, could spread to more areas of the world.
“The world is continually changing and we are seeing vectors moving to new areas. Governments and health organisations, and individuals, need to be alert to these changes,” said Lindsay.
Lindsay, who has been researching the tools for malaria prevention such as treated bednets, said that in some areas this has already started to happen.
“The Asian Tiger mosquito, for example, is spreading across the northern shores of the Mediterranean, where it wasn’t found 20 years ago. It can transmit diseases such as Chikungunya that won’t kill, but are pretty unpleasant,” explained Lindsay.
“That is a concern for countries such as Spain and France, for example, and potentially the UK in the future, depending on environmental changes.”
According to University of Exeter associate lecturer Dominic Henri, one type of malaria, Plasmodium vivax, which is found in Asia and is less dangerous than its African cousin Plasmodium falciparum, did previously exist in Europe.
“The symptom people ascribed to miasma, people think was actually plasmodium vivax,” explained Henri, adding that in areas such as Italy this was wiped out because “proper drainage systems and proper houses” were built that stopped its transmission.
Because of this and general increased urbanisation, Henri does not see a return of malaria in Europe due to a rise in temperatures as the wet, leafy environments that the insects thrive in no longer exist in large quantities.
The exception to this is in areas high above sea level, where changes in temperatures have allowed mosquitoes to venture further than they previously have managed. “There’s been a big increase in the altitude that you can get malaria,” explained Henri. “That is global warming, increasing the altitude.”
However, he explained that the impact of climate change was likely to come more from rising sea levels. “You’d be more likely to get freshwater wetlands that would allow mosquitos to survive,” said Henri.
Perhaps of greater concern, though, is that mosquitoes are increasingly building up a resistance to the most common anti-malarial treatment taken by travellers, chloroquine prophylaxis, meaning that the disease is being carried home to non-malarial countries where it can survive for the summer, infecting others who have remained at home.
Henri explained that even those who have followed their treatment regiment properly can still get the illness, and cited a study that found a 22% increase in malaria cases returning from holidays to the Indian subcontinent.
While individuals can do little to fight climate change on their own, he stressed that travellers to malaria-infection regions must make sure that they do complete the full course of their antimalarial treatment as not finishing it can aid resistance among mosquitoes.
Although he acknowledged that the tablets were expensive, they are an important consideration for any trip to an infected region. He also highlighted to benefit of treated bednets, which can easily be purchased before departure.
“Before you go you need to know if it’s in a malaria area, and before you go you need to take the prophylaxis and you need to take it correctly,” said Henri.