As bats hibernate through the winter, so does rabies
Every year, in mid-September, big brown bats throughout Colorado head for their favourite roosts, where they will spent the winter in hibernation. But some of the bats won’t sleep alone – they are carrying the rabies virus, and it will also hibernate through the winter in its slumbering host.
The rabies virus is a killer. Infections are almost always fatal, and around 55,000 people around the world succumb to the virus every year. Dogs are the leading carriers, but in North America, vaccination programmes have effectively eliminated dog rabies. Bats are another story – they are far more difficult to vaccinate and they have overtaken man’s best friend as the leading cause of American rabies.
Now, Dylan B. George from Colorado State University has shown that the rabies virus, by hibernating alongside the big brown bats, gets a free pass to the next generation.
In bats, the rabies virus isn’t always lethal; some of them develop antibodies that neutralise the virus and render them immune. Come the winter, these survivors take off for hibernation roosts. Their metabolism slows to a crawl and their body temperatures drop. These cooler temperatures also slow the development of the rabies virus so it ends up hibernating along with its host.
In early spring, the bats slowly rouse from their winter naps. For a while, the females are prone to shutting their bodies down again, but in the mean time, they form tight-knit colonies. In such close groups, viruses like rabies are easily transmitted from one bat to another. When the bats wake properly, they fly off to form maternity colonies. Again, they cluster in close quarters and they give birth to their pups. That gives rabies a chance to infect an entirely new generation of hosts, whose immune defences haven’t been trained against the virus yet.
George modelled all of this using data from a five-year project that tracked around 15,000 big brown bats in roosts around the city of Fort Collins. He used this big bat census to create a mathematical model, which simulated the rise and fall of the rabies virus in these hosts.
The model explained why rabies shows up in bats with a distinctive seasonal trend, peaking between spring and autumn, when the cycle of infection begins again. The model also showed why hibernation is so important for both the bats and the virus. When George took it out of his simulation, he found that the rabies virus quickly cut through the bat populations, causing them to crash. By hibernating, the bats manage to save themselves until they can raise a new generation – something that also benefits the virus.
These results have implications for understanding and controlling rabies, but they have a broader importance. Bats are natural reservoirs for many deadly viruses including rabies, Ebola, henipaviruses, and coronaviruses such as SARS. George thinks his model can be easily adapted to predict how new emerging diseases will behave in bat hosts.
Reference: George, Webb, Farnsworth, O’Shea, Bowen, Smith, Stanley, Ellison & Rupprecht. 2011. Host and viral ecology determine bat rabies seasonality and maintenance. http://dx.doi.org/10.1073/pnas.1010875108
Go Further
Animals
- How can we protect grizzlies from their biggest threat—trains?How can we protect grizzlies from their biggest threat—trains?
- This ‘saber-toothed’ salmon wasn’t quite what we thoughtThis ‘saber-toothed’ salmon wasn’t quite what we thought
- Why this rhino-zebra friendship makes perfect senseWhy this rhino-zebra friendship makes perfect sense
- When did bioluminescence evolve? It’s older than we thought.When did bioluminescence evolve? It’s older than we thought.
- Soy, skim … spider. Are any of these technically milk?Soy, skim … spider. Are any of these technically milk?
Environment
- Are the Great Lakes the key to solving America’s emissions conundrum?Are the Great Lakes the key to solving America’s emissions conundrum?
- The world’s historic sites face climate change. Can Petra lead the way?The world’s historic sites face climate change. Can Petra lead the way?
- This pristine piece of the Amazon shows nature’s resilienceThis pristine piece of the Amazon shows nature’s resilience
- Listen to 30 years of climate change transformed into haunting musicListen to 30 years of climate change transformed into haunting music
History & Culture
- Meet the original members of the tortured poets departmentMeet the original members of the tortured poets department
- Séances at the White House? Why these first ladies turned to the occultSéances at the White House? Why these first ladies turned to the occult
- Gambling is everywhere now. When is that a problem?Gambling is everywhere now. When is that a problem?
- Beauty is pain—at least it was in 17th-century SpainBeauty is pain—at least it was in 17th-century Spain
Science
- Here's how astronomers found one of the rarest phenomenons in spaceHere's how astronomers found one of the rarest phenomenons in space
- Not an extrovert or introvert? There’s a word for that.Not an extrovert or introvert? There’s a word for that.
- NASA has a plan to clean up space junk—but is going green enough?NASA has a plan to clean up space junk—but is going green enough?
- Soy, skim … spider. Are any of these technically milk?Soy, skim … spider. Are any of these technically milk?
Travel
- Could Mexico's Chepe Express be the ultimate slow rail adventure?Could Mexico's Chepe Express be the ultimate slow rail adventure?
- What it's like to hike the Camino del Mayab in MexicoWhat it's like to hike the Camino del Mayab in Mexico