THE BLOG
10/11/2012 09:38 am ET Updated Dec 11, 2012

The Spread of Diseases in a Changing World

In July 2012, I was in Coldfoot, Alaska, a small hamlet along the Dalton Highway above the Arctic Circle. Speaking with some of the long time residents, I heard an all too familiar story: Things are just not the way they were when they were kids. The permafrost is melting, the weather is different, and somehow things just don't seem right. I have had the opportunity to travel extensively and have heard similar stories from people in rainforest regions of Africa and Peru as well as India, Turkey, Europe and the United States. We all know it. There are fewer forests, more people and more pollution.

So much of the news these days plays into our fears. A catchy headline will often evoke thoughts of a loss or major disaster, and we are hounded regularly by information overload that seems ever escalating in exigency. There is a lot of coverage of potential environmental disasters associated with global climate change, but are the fears justified?

In Alaska, my colleagues and I examined birds to determine whether climate change is driving diseases, in particular avian malaria, north as the earth warms. And in this case, we found there may be reason for concern.

There are at least 40 known species of Plasmodium, the parasite that causes malaria, that can infect birds. In all cases, malaria is transmitted by mosquitoes, and there are a lot of mosquitoes in Alaska! Previous research established that migratory birds in Alaska had malaria, but our team, led by San Francisco State University post-doctoral fellow Claire Loiseau, wanted to know whether the disease was being transmitted locally. Our work, published in the journal PLoS ONE in September, shows that, yes, avian malaria is transmitted in Alaska. It is found both in young birds that have not yet migrated and birds that live there throughout the year, such as the Black-capped chickadee. We found infected birds in Anchorage and Fairbanks, but not farther north in Coldfoot. However, some sophisticated climate modeling showed that by 2080, avian malaria will proceed northward, passing the Arctic Circle and Coldfoot, but not quite reaching the Arctic Ocean.

What does this mean? It adds to the list of possible unfortunate outcomes of climate change. Unfortunately, we do not know when avian malaria arrived in Alaska, but we do know the disease devastated bird populations of Hawaii when it arrived there in the mid-19th century. We know penguins in zoos die of avian malaria regularly. In many other bird species the disease is not lethal, but may affect their fitness, such as how many eggs they lay. It appears that birds that have never been exposed to malaria in their evolutionary history, akin to those in the High Arctic, are the most susceptible. With funding from the National Geographic Society, our team, along with researchers at UC Davis, is now trying to identify which species of mosquitoes are responsible for transmitting avian malaria in Alaska. We also plan to eventually decipher the role increasing temperatures will play in the parasite's life cycle. We hope to make strides in clarifying the spread of the disease but, more importantly, highlight a major problem associated with rapid environmental changes.

Perhaps even more pressing than global climate change is the rapid deforestation of the planet. In Africa, deforestation is omnipresent, with huge logging trucks clogging the newly paved roads of Cameroon and other sub-Saharan nations. How does this affect disease transmission? With the Center for Tropical Research at UCLA, we have been studying avian malaria in African rainforest birds and found that the prevalence of the parasites changes in deforested regions. Some malaria species increase, and others decrease. But again, we have little knowledge about the virulence of these parasites, and how the different strains may affect the various species of birds. These avian malarias will most likely never spread to humans, but they do serve as a model to understand how rapid environmental change may affect the transmission of diseases relevant to all species on the planet.

So are the headlines justified? Should we be worried about environmental changes and diseases? We now know that environmental changes contributed to the emergence of one of the world's deadliest diseases, HIV/AIDS, from African chimpanzees. In the case of avian malaria, there are no definite answers, but the evidence suggests we should keep alert. The disease could affect threatened bird populations and it serves as a good model to study the phenomenon of disease emergence in general. The National Science Foundation has sponsored a group of researchers called a Research Coordination Network to study malaria in wildlife worldwide. Eventually with deeper scientific studies from concerted efforts, I predict future headlines will outline concrete solutions and definite answers about how we can work together to minimize the risks of disease emergence.

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