The year 2014 was marked with the emergence and spread of diseases at an unprecedented rate. The Ebola epidemic that severely hit West Africa, for instance, has been described as the worst outbreak of its kind in history.
Now, scientists claim that the appearance of infectious diseases, such as Ebola and the West Nile virus, in new places and new hosts has something to do with our warming planet.
Daniel Brooks from the University of Nebraska State Museum of Natural History has claimed that these health problems are a predictable result of climate change.
In a study published in the Philosophical Transactions of the Royal Society B on Feb. 16, Brooks and zoologist Eric Hoberg from the U.S. National Parasite Collection, warned that humans can anticipate the emergence of more diseases in the future as climate change leads to the alteration of habitats.
This alteration leads to wildlife, livestock, crops and humans getting in contact with pathogens that they are susceptible to but have not been previously exposed to.
Brooks, whose research studies are primarily focused on tropical parasites, and Hoberg, who has mainly worked in the Arctic regions, have both observed the appearance of species that did not previously live in the area and also the exodus of other species. The changes in habitat result in animals being exposed to new parasites and pathogens.
"Over the last 30 years, the places we've been working have been heavily impacted by climate change," Brooks said. "Even though I was in the tropics and he was in the Arctic, we could see something was happening."
Brooks cited the example of the capuchin and spider monkeys that were hunted to extinction in some regions in Costa Rica. Their disappearance has led to their parasites switching to howler monkeys. Some lungworms have also moved habitats and shifted hosts in the Canadian Arctic.
Previous theories posited that when hosts and pathogens become more tightly adapted, emerging diseases become rare because they have to wait for the right random mutation to happen. It appears now that such jump occurs faster than previously thought with pathogens, which are highly adapted to a host, able to shift to new ones given the right circumstances.
Brooks likewise said that because they have not yet developed resistance, new hosts tend to be more susceptible to infection and get sicker from it.
"Episodic shifts in climate and environmental settings, in conjunction with ecological mechanisms and host switching, are often critical determinants of parasite diversification, a view counter to more than a century of coevolutionary thinking about the nature of complex host-parasite assemblages," the researchers wrote.