More infectious diseases emerging because of climate change

February 15, 2015
In some areas of Costa Rica, howler monkeys like this one are infected with parasites once limited to capuchin and spider monkeys. After humans hunted capuchins and spider monkeys out of existence in the region, the parasites immediately switched to howler monkeys, where they persist today. Credit: Photo courtesy Daniel Brooks Photography

The appearance of infectious diseases in new places and new hosts, such as West Nile virus and Ebola, is a predictable result of climate change, says a noted zoologist affiliated with the Harold W. Manter Laboratory of Parasitology at the University of Nebraska-Lincoln.

In an article published online today in conjunction with a special issue of the Philosophical Transactions of the Royal Society B, Daniel Brooks warns that humans can expect more such illnesses to emerge in the future, as shifts habitats and brings wildlife, crops, livestock, and humans into contact with pathogens to which they are susceptible but to which they have never been exposed before.

"It's not that there's going to be one 'Andromeda Strain' that will wipe everybody out on the planet," Brooks said, referring to the 1971 science fiction film about a deadly pathogen. "There are going to be a lot of localized outbreaks putting pressure on medical and veterinary health systems. It will be the death of a thousand cuts."

Brooks and his co-author, Eric Hoberg, a zoologist with the U.S. National Parasite Collection of the USDA's Agricultural Research Service, have personally observed how climate change has affected very different ecosystems. During his career, Brooks has focused primarily on parasites in the tropics, while Hoberg has worked primarily in Arctic regions.

Each has observed the arrival of species that hadn't previously lived in that area and the departure of others, Brooks said.

"Over the last 30 years, the places we've been working have been heavily impacted by climate change," Brooks said in an interview last week. "Even though I was in the tropics and he was in the Arctic, we could see something was happening." Changes in habitat mean animals are exposed to new parasites and pathogens.

For example, Brooks said, after humans hunted capuchin and spider monkeys out of existence in some regions of Costa Rica, their parasites immediately switched to howler monkeys, where they persist today. Some lungworms in recent years have moved northward and shifted hosts from caribou to muskoxen in the Canadian Arctic.

But for more than 100 years, scientists have assumed parasites don't quickly jump from one species to another because of the way parasites and hosts co-evolve.

Brooks calls it the "parasite paradox." Over time, hosts and pathogens become more tightly adapted to one another. According to previous theories, this should make emerging diseases rare, because they have to wait for the right random mutation to occur.

However, such jumps happen more quickly than anticipated. Even pathogens that are highly adapted to one host are able to shift to new ones under the right circumstances.

Brooks and Hoberg call for a "fundamental conceptual shift" recognizing that pathogens retain ancestral genetic capabilities allowing them to acquire new hosts quickly.

"Even though a parasite might have a very specialized relationship with one particular host in one particular place, there are other hosts that may be as susceptible," Brooks said.

In fact, the new hosts are more susceptible to infection and get sicker from it, Brooks said, because they haven't yet developed resistance.

Though resistance can evolve fairly rapidly, this only changes the emergent pathogen from an acute to a chronic disease problem, Brooks adds.

"West Nile Virus is a good example - no longer an acute problem for humans or wildlife in North America, it nonetheless is hhere to stay," he said.

The answer, Brooks said, is for greater collaboration between the public and veterinary health communities and the "museum" community - the biologists who study and classify life forms and how they evolve.

In addition to treating human cases of an emerging disease and developing a vaccine for it, he said, scientists need to learn which non-human species carry the pathogen.

Knowing the geographic distribution and the behavior of the non-human reservoirs of the pathogen could lead to public health strategies based on reducing risk of infection by minimizing human contact with infected animals, much likethose that reduced the incidence of malaria and yellow fever by reducing human contact with mosquitos.

Museum scientists versed in understanding the evolutionary relationships among species could use this knowledge to anticipate the risk of the pathogen becoming established outside of its native range.

Brooks, who earned his bachelor's and master's degrees from the University of Nebraska-Lincoln, was a zoology professor at the University of Toronto for 30 years until he retired early in 2011 to devote more time to his study of emerging infectious disease. In addition to being a senior research fellow with UNL's Manter Laboratory, he is a visiting senior fellow at the Universidade Federal do Parana, Brazil, funded by the Ciencias sem Fronteiras (Sciences without Borders) of the Brazilian government, and a visiting scholar with Debrecen University in Hungary.

Brooks' and Hoberg's article, "Evolution in action: climate change, biodiversity dynamics and emerging infectious disease," is part of a Philosophical Transactions of the Royal Society B issue on "Climate change and vector-borne diseases of humans," edited by Paul Parham, a specialist in infectious disease epidemiology at Imperial College in London.

"We have to admit we're not winning the war against emerging diseases," Brooks said. "We're not anticipating them. We're not paying attention to their basic biology, where they might come from and the potential for new pathogens to be introduced."

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13 comments

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Shootist
2.5 / 5 (11) Feb 15, 2015
More infectious diseases . . .


Climate Change: Is there anything it cannot do?

Warmer climates have always been kinder to man than the Wurm (won't display the u-umlaut)
mememine69
1.4 / 5 (11) Feb 15, 2015
History has a special place for you climate blamers.
Deny this;
The pause in global warming is now old enough to vote and deniers have successfully prevented climate action for 34 years and Occupywallstreet now does not even mention CO2 in its list of demands because of the bank-funded and corporate run carbon trading stock markets ruled by politicians.
Nice work girls, climate blame has done to the left what Bush and his false wars did for the neocons.
Deny that.
verkle
Feb 15, 2015
This comment has been removed by a moderator.
Vietvet
4.3 / 5 (12) Feb 15, 2015
I truly feel sorry for these so-called scientists that try to attach any change and evil on climate. Such a narrow-minded world view.


No one is more narrow minded than religious fundamentalists.
Maggnus
4.3 / 5 (11) Feb 15, 2015
I truly feel sorry for these so-called scientists that try to attach any change and evil on climate. Such a narrow-minded world view.


No one is more narrow minded than religious fundamentalists.


Well, the willfully stupid give them a run for their money!
Climate Change: Is there anything it cannot do?

Warmer climates have always been kinder to man than the Wurm (won't display the u-umlaut)
See what I mean?
samohta
1.4 / 5 (9) Feb 15, 2015
If tropical diseases spread due to warmer climates/warmer temperatures, then logically illnesses associated with colder climates/colder temperatures should decrease. So long influenza!
mbee1
1.7 / 5 (11) Feb 15, 2015
More junk articles from people who would do well as the mad hatter in Oz. The parasites were most likely already in the monkeys in question. they simply just like fleas prefered a different host Fleas like rats, mice, cats and dogs but will bit humans if no better food source is available. Why should climate have made any different here especially as the climate has not changed where these animals live.
dcbru
1.9 / 5 (13) Feb 15, 2015
Climate change is making my hemorrhoids worse; it must be stopped!
Rustybolts
1.5 / 5 (4) Feb 16, 2015
It's not that bad of a article. It kinda makes sense but it's just a theory. Nothing proven at all.
greenonions
3.7 / 5 (9) Feb 16, 2015
Verkle
I truly feel sorry for these so-called scientists that try to attach any change and evil on climate. Such a narrow-minded world view.


And you display the heart of a huge problem with this comment. Medical science spends it's time studying the pathologies that plague us - and then developing counter strategies. Literally trillions of hours have gone into this endeavor, and of course the study will go on for ever. Every day there is another article on Physorg - highlighting another advance in a medical science - working on cancer, and parkinsons, etc. One major aspect of this process is the study of infectious diseases. http://www.scient...us-gain/ Our climate is warming (fact), and that warming obviously has to be a part of this study. You then accuse the very scientists who are trying to understand our world - and bring us this progress - of being narrow minded. cont.
greenonions
3.6 / 5 (9) Feb 16, 2015
cont. Re-read this article, and look at the credentials of the one scientist spotlighted by this article. This is one of millions of scientists who are (and have been) moving our species forward in this great endeavor. What right do you have to dismiss this science - and to insult these scientists - by calling them narrow minded? Please don't side step this direct question.
antigoracle
2.1 / 5 (7) Feb 16, 2015
Truly, the only parasites to emerge due to climate change, are those hypocrites in the AGW Cult. Like the do-as-I-say-not-as-I-do followers of the False "Profit" Al.
Maggnus
3.9 / 5 (7) Feb 16, 2015
If tropical diseases spread due to warmer climates/warmer temperatures, then logically illnesses associated with colder climates/colder temperatures should decrease. So long influenza!
Except that influenza is not a cold climate disease, it probably originates in south-east Asia: http://abcnews.go...=5677533

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