Via the Pacific Institute for Climate Studies in Victoria, BC: PICS Climate News Scan-October 16, 2014.
When climate change meets Ebola: Vector-borne diseases in a warming world
The Ebola virus has now infected over 8000 people and claimed over 3,000 lives in the most deadly outbreak to date. Ebola is a virus that lives in wild animals, and makes the jump to the human population when humans consume bush meat or come in contact with fluids from wild animals that are infected.
This jump, which can trigger an outbreak, is more likely to happen under certain conditions. One is deforestation, which brings humans more into contact with ‘survivor’ species such as bats that are likely to carry the disease. A second is drought or food insecurity, which increases the likelihood that people will turn to food sources such as bush meat for sustenance. And a third factor for Ebola is a sudden shift from dry to wet conditions, seen during outbreaks in the 1990s.
Does this mean that climate change will affect the likelihood of such outbreaks? Not necessarily. But while precipitation patterns in Africa are largely uncertain in future warming scenarios, there are projected increases in both drought, and warm temperatures that, depending on location, can lead to both more evaporation and precipitation. These suggest favourable scenarios for this switch. At present, however, there is no clear link between climate change and the Ebola epidemic that is that afflicting western Africa.
In contrast, the link between climate change and the incidence of certain other pathogens is well established. Malaria distribution patterns are anticipated to change under a changing climate, potentially increasing its death toll. So will trachoma. Water-borne cholera survives best in warmer temperatures. Dengue fever, carried by mosquitoes, is the fastest-growing vector-borne pathogen.
Vector-borne diseases - those carried by rats, ticks, fleas or mosquitoes - are most likely to be affected because climate change affects whole ecosystems, shifting ranges and bringing humans into contact with new pathogens for which they may not have resistance.
One that is causing some worry in Canada is Lyme disease, a bacterial infection introduced to humans by tick bites. The disease, if not diagnosed and treated early can affect the joints, heart, and central nervous system and be quite debilitating.
The bacteria responsible for Lyme disease are carried by ticks, and as temperatures warm ticks are moving north. Outbreaks in Atlantic Canada, southern Ontario and British Columbia (BC) have led to calls to develop a national strategy on Lyme disease.
While the impact of Lyme disease in Canada pales in the face of the Ebola epidemic in Africa, the growing incidence of the disease in this country reinforces the need to understand and deal with the human health implications of a changing climate.