When deer mice attack


Graying, skeletal aspens and fluid-filled lungs. No connection, right?


Photo courtesy Flickr user Colby Gutierrez-Kraybill

This little guy is a deer mouse. Cute, sure. But deer mice are the primary vectors for the "sin nombre" form of hantavirus -- a nasty bug transmitted primarily through the rodent's feces and urine which causes flu-like symptoms and, in later stages of infection, fills the lungs with fluid, resulting in death in more than a third of cases. (For more info, check out this rundown of a major outbreak in the Southwest from NASA's Earth Observatory.)

And it turns out Sudden Aspen Decline -- a largely drought-spurred die-off of aspens in the West -- may be upping the risk of hanta infection, according to physiological ecologist Erin Lehmer and colleagues at Fort Lewis College in Durango, Colo. In areas with lots of dead trees, the researchers found that deer mice were almost three times more likely to carry the virus than those in aspen stands that stayed healthy, reports ScienceNews:
In study sites that had lost at least two-thirds of their aspens, the researchers found fewer species of small mammals. The most abundant of those was the deer mouse ... Lehmer speculated that infection might have risen among deer mice as their growing dominance in the landscape let them encounter each other more frequently and get into more mouse fights.

The prospect of mouse fights may seem titter-worthy, but the trend implied by Lehmer's research is a sobering one. As climate change warms the West, nasty droughts like the one that parched the region in 2002 and kicked off the dramatic round of SAD that researchers have been following are likely to come again.

And hanta certainly isn't the only horror-show disease to rear its ugly head in the West in recent years whose increase in prevalence is likely due at least in part to climate change. As of July last year, some 60 cases of a fungal illness once thought to be exclusively tropical had been reported in the Northwest, according to Scientific American. Known as Cryptococcus gattii, the fungus attacks the nasal cavity and can lead to meningitis and other ill effects; of the 45 cases with known outcomes, 9 people died of the bug.

Then there are those widespread outbreaks of West Nile virus that have occurred across the West over the past decade, which researchers have linked with warmer temperatures, elevated humidity, and heavy precipitation -- all likely to increase in areas of the West as climate change proceeds.

And let's not forget the real creepies like Leishmaniasis, a protozoal infection spread by sand flies which causes ulceration of the skin and can damage the liver and spleen. In recent years, it's spread from tropical regions north across the U.S. border, including into Arizona. And my personal favorite (and by favorite I mean the one that gives me the fiercest willies) -- brain-eating amoebas, which turned up in the Southwest in 2007 when a fourteen-year old boy died after he picked them up swimming in the ever-warmer shallows of Lake Havasu in Arizona. Yikes.

All this should be delivered with a healthy dose of perspective, of course: In the long run, you're still much more likely to succumb to that Big Mac you had for lunch than to a mousy little package o' death.

Sarah Gilman is High Country News' associate editor.