How Climate-Change Spreads Mosquito-Borne Diseases

By Andrew Mambondiyani

Antwerp, Belgium– Climate-change is contributing to the spreading and worsening of mosquito-borne diseases, experts have said.

Various experts at 10th European Congress on Tropical Medicine and International Health (ECTMIH) in Antwerp, Belgium concurred that climate-change was contributing to the spread of mosquito-borne diseases.

These mosquito-borne diseases include Zika virus, West Nile virus, Chikungunya virus, dengue, yellow-fever, and malaria.

Tiago Canelas Ferreira, a Ph.D. candidate in Global Health and Sustainability at the School of Public Health, the University of São Paulo in Brazil, said it was clear that part of the malaria problem depends on environmental factors so a change in the climate would change malaria transmission.

Ferreira said three components might change and these elements include host, vector, and parasite.

“Faster rates of reproduction, shorter time of development and other changes in times might happen due to climate changes as we know for a lot of research mosquitoes and parasites adapts themselves to different climates, and they did it for the last 10 000 years at least,” Ferreira said.

He said the same rationale for humans, changes in climate might represent changes in the behaviours, switching ways of life and house behaviours.

“The important point is that climate-change won’t make malaria disappear. In my opinion, it will alter dynamics and therefore during a period populations will be much more vulnerable if prevention isn’t applied,” he said.

He also said climate-change would bring some changes that would make difficult the fight against the disease.

“We’ll have to think differently [from what we] are used to, and this isn’t easy. This adaptation to new scenarios will cost money and resources, that’s why we have to start to change the paradigm from malaria risk to malaria vulnerability and make populations more resilient [to] decrease the impact of this climate changes,” he added.

Veerle Vanlerberghe from the Institute of Tropical Medicine in Antwerp, Belgium, said climate-change was among the factors causing the fast spread of mosquito-borne diseases.

“Yes, climate change is contributing to that ( the spread of mosquito-borne diseases). But also the uncollected garbage in urban areas has created breeding places for mosquitoes,” Vanlerberghe said.

Another expert, Joe Brew said the effects of climate change on the fight against malaria make everything a bit more unpredictable.

Brew said when climate conditions change, mosquito habitats and behaviours also change.

“This means that malaria (and other mosquito-borne illnesses) will stop being a problem in some areas, but it also means that the disease may emerge or re-emerge in places which are not familiar with them, have not recent history of vector control, and whose surveillance systems are not equipped for handling them,” Brew said.

He said a recent example was the re-emergence of malaria in Italy.

“A similar phenomenon is taking place with the spread of Dengue in the Caribbean. Can these be attributed to climate change? I’m not sure, but I do believe that the phenomenon of unexpected changes in the epidemiology of these diseases will become more common,” he said.

Brew said, on the one hand, climate-change could provoke conditions where more resources going to malaria are necessary; on the other hand, the opportunity cost of spending on malaria might be greater due to the fact that climate change is also likely to cause conditions like drought, migration, and famine which will compete for funding resources

And a study published by the journal, BioMed Central revealed that the advent of climate change especially increases in temperature, threatens to complicate the situation by extending the geographical distribution of malaria globally, in parts of Europe, Asia and Africa.

The report said insecticide residual spraying has been documented as an effective way to control malaria and has been adopted globally by the WHO and national governments.

However, the report added, both insecticide resistance and climate change threaten to reverse the progress made by insecticide residual spraying in malaria control.

“Resistance has been reported in all four classes of insecticides approved by the WHO for vector control intervention,” the report said. “Variability of environmental temperature is suspected to complicate the situation through alteration in the genetic structure, and enzyme and protein profiles of mosquitoes”.

In Zimbabwe, the study also revealed, little research had been done on the interaction between climate change, temperature variability and insecticide resistance in malarial mosquitoes over time.

But researches have shown that mosquitoes were migrating from low to high altitude areas along river valleys in Zimbabwe the country’s “highlands will be climatologically habitable to malarial mosquitoes by 2015.”