A high-profile donation from the Bill and Melinda Gates Foundation threw a spotlight on neglected tropical diseases (NTD) earlier this year, but many fear progress toward eliminating some of these diseases could be scuppered by climate change.
NTDs are a group of chronic, disabling conditions - ranging from bacterial and parasitic infections to snakebites - affecting more than a billion people worldwide. These diseases contribute to an ongoing cycle of poverty and stigma, with many infected people unable to work or attend school. Controlling NTDs will be critical to the health and economic growth of developing countries - which are also disproportionately vulnerable to climate change.
Mark Booth, deputy director of the Wolfson Research Institute for Health and Wellbeing, said, “There’s a great deal of uncertainty. We’re not sure how much climate change will affect [disease] transmission rates. We’re not sure what will happen with the environment and how people and governments will adapt.”
Many researchers are concerned changes in rainfall patterns could result in a loss of “endemic stability” for diseases carried by mosquitoes, ticks and other disease hosts, and that environmental conditions could become favourable for disease transmission.
Rising average annual temperatures have already been blamed for increasing numbers of malarial mosquitoes at higher altitudes in Tanzania and Kenya. Increasing numbers of malaria cases have also been reported in the highlands of Madagascar, Rwanda and Ethiopia.
While malaria is not considered an NTD, similar patterns of expansion are feared for other tropical diseases carried by mosquitoes and flies. Temperature, rainfall and runoff could also affect the growth and spread of microbial diseases.
But many researchers believe there is simply not enough information available to warrant alarm.
Speakers at the International Society for Neglected Tropical Diseases (ISNTD) Bites conference in London, in October, were divided over the extent to which climate change is already having an impact on NTD control and whether it should be given priority over other disease drivers.
World Health Organization (WHO) senior scientist Diarmid Campbell-Lendrum said, “Unfortunately I think the discussion has got in to a rather unconstructive, polarized debate. There are those on one side that blame all changes in NTDs on climate change - a disaster scenario - and those that think climate change has nothing to do with it at all.”