Topic: Lyme Culprits: The Story of the Mouse and the Fragmented Forest
CaliforniaLyme
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Lyme Culprits: The Story of the Mouse and the Fragmented Forest
By: Megan S. Smith 05/09/2007
Four little white feet and a long tail dangled from Roscoe's mouth. The dog had eaten a vector. A bacterium-carrying vector for Lyme disease, that is, known around zoological circles as the white-footed mouse.
The brown mouse with its big black bulging eyes is the primary carrier - or vector - for the spread of Lyme disease in the U.S. From the mouse the bacterium has an arduous, seemingly impossible trip to make before infecting people, leaving them miserable for days, months, even years.
Lyme disease is the most common tick-borne illness in the U.S. and Europe. Caused by bacterium Borrelia burgdorferi, it was discovered in 1981 following a bizarre outbreak of arthritis in children years earlier in Lyme, Connecticut. Its various symptoms are difficult to diagnose and harder still to cure if left untreated.
According to Dr. David Gaines, epidemiologist and tick tracker for the Virginia Department of Health, here is how the story unfolds.
White-footed mice are quite common in forested areas and the main meal ticket for the black-legged tick, commonly known as the deer tick.
When larval ticks feed on infected mice, they turn into infected nymphal ticks - the primary link between Lyme disease and humans.
Here enters the white-tailed deer, also lovers of the forest and accomplices for spreading Lyme. The adult tick prefers deer blood to that of the white-footed mouse, so it transfers vehicles and motors out. The faster paced deer allows adult ticks to lay its eggs in far away lands.
Here enters the bulldozers. Also lovers of forests, they chop, chop, chop down trees, opening forests up to suburban sprawling. This "fragmented forest" is a happy home to deer because of the plentiful food. In fact, deer thrive there.
Unlucky for people, the infected white-footed mouse likes to sprawl along with dozers, houses and deer - the latter wiping out grass, honeysuckle, Rappahannians gardens, etc., along the way.
And so, Lyme-infected ticks have been meandering slowly from New England to Virginia aboard the white-tailed deer/white-footed mouse express for several decades. In fact, Virginia appears to be dividing the Lyme-heavy north from the Lyme-light south, making our Commonwealth a type of "Mason-Dixon Lyme line."
The deer-mouse caravan is aided in part by something lacking any feet at all: Acorns. Deer like acorns. So do mice, according to Gaines, which become more plentiful soon after ingestion. Researchers have noted - due to the two-year life cycle of ticks - an increase in Lyme two years following a heavy acorn crop.
Long-time Rappahannock resident E.C. "Pete" Jenkins said 2006 was a very large acorn year, "the biggest I ever saw." So 2008 could possibly be a whopper for deer ticks and Lyme incidence in the county.
According to three Massachusetts-based scientists, here are the basics to a deer tick's 2-year life cycle: Adult ticks, following a yummy blood meal in the fall, leave the deer to lay eggs in the ground, which hatch the following spring; larval ticks prefer to dine on mice in the late summer, whereas nymphal ticks abandon their Mice Taxis late spring and early summer to feed on unsuspecting humans.
It is this nymphal tick - the tiny little dot not more than a millimeter long -that primarily transfers Lyme to humans. And this is bad news for man because, due to their size, nymphs are often overlooked as moles and even specks of dirt.
While it is possible to become Lyme infected by adult ticks later in the fall, the spring/summer time period should be high-alert season for suspicious new "moles" popping up from nowhere or fast moving flecks of dirt.
Dispensing of ticks can be a real challenge. Master chef Heidi Morf of "Four and Twenty Blackbirds" fame tried to get rid of a tick by tossing it into a sink with a chaser of water. When Vinnie DeLuise entered the bathroom later, he was surprised to find "the little bugger climbing its way back out of the drain!"
As for Roscoe-the-Vector-Dog, can a dog get Lyme by eating a white-footed mouse? Can humans contract Lyme from a canine kiss? Is Roscoe a ticking Lyme-bomb waiting to explode? These are all questions needing further investigation.
But for right now, suffice to say that Vector Dog is going to get a really good sudsy bath and a big mouth full of soap.
@Times Community Newspapers 2007
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