Researchers find no safe place to sit in California tick-infested forest

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Several members of a group I belong to have been discussing if ticks are

in trees - including *Christmas Tress*.......

blessings

Shan

 

Researchers find no safe place to sit in California tick-infested forest

By Sarah Yang, Media Relations

_http://berkeley.edu/news/media/releases/2004/04/08_tick.shtml_

(http://berkeley.edu/news/media/releases/2004/04/08_tick.shtml)

 

 

BERKELEY – After a long hike through some of California's forests, it may

be tempting to rest on a log or lean against a tree. Wrong move, say

researchers at the University of California, Berkeley, who found that such

activities may increase the risk of acquiring ticks harboring the Lyme disease

bacterium.

 

 

UC Berkeley researcher Denise Steinlein demonstrates the three actions

found to be riskiest for acquiring the western black-legged tick: leaning

against a tree, carrying wood and sitting on a log. (Photos by Robert Lane)

 

 

" We sat on logs for only five minutes at a time, and in 30 percent of the

cases, it resulted in exposure to ticks, " said Robert Lane, professor in

the Division of Insect Biology at UC Berkeley's College of Natural Resources

and lead investigator of the study. " It didn't matter if we sat on moss or

the bare surface; the ticks were all over the log surface. The next

riskiest behavior was gathering wood, followed by sitting against trees, which

resulted in tick exposure 23 and 17 percent of the time, respectively. "

 

 

The study, published in the current issue of the Journal of Medical

Entomology, is the first quantitative analysis of human behaviors that may

increase the risk of tick exposure in California's hardwood forests. The paper

has come just weeks before the start of northwestern California's nymphal

tick season, which begins in early spring and continues into summer.

 

 

[PICTURE]

Once on a person, the nymph of the western black-legged tick (shown

enlarged in inset) is readily overlooked because of its minute size.

 

 

The western black-legged tick, found primarily in the far western United

States as well as in British Columbia, is the primary carrier of the

corkscrew-shaped spirochete Borrelia burgdorferi, a bacterium named after its

discoverer, Dr. Willy Burgdorfer. B. burgdorferi is responsible for Lyme

disease, which can lead to debilitating symptoms in humans. Most human cases of

Lyme disease in northwestern California appears to be transmitted by young

nymphal ticks, which are notoriously difficult to detect because they are as

small as poppy seeds.

 

 

Lane and study co-author Denise Steinlein, a UC Berkeley graduate student

in insect biology, trekked through a hardwood forest at the UC Hopland

Research and Extension Center in southeastern Mendocino County to conduct the

field trials. The area, dominated by California black oak, is endemic for

Lyme disease.

 

 

Jeomhee Mun, a UC Berkeley research specialist in insect biology, is

another co-author of the paper.

 

 

Lane and Steinlein conducted the experiments on two back-to-back days in

three consecutive weeks in 2002 between late May and mid-June. Decked out in

white clothing from top to bottom, with pant legs tucked into white socks

and seams sealed with duct tape, the researchers set out to learn how

people might acquire nymphal ticks.

 

" If we're going to develop effective strategies and educational programs

for the prevention of Lyme disease, it is critical that we understand how

people are exposed to the ticks that transmit the bacteria in the first

place, " said Lane. " We intentionally looked at behaviors that people would

typically engage in while spending time in the woods. "

 

 

The researchers sat on logs, sat against trees, gathered wood, walked

through leaves, sat still on leaf litter and sat and stirred up leaf litter for

set amounts of time. Lane noted that turkey hunters can easily spend up to

an hour or longer sitting with their backs against trees while trying to

call in toms during the spring hunting season.

 

 

After each activity, in scenes strikingly reminiscent of primate grooming

behavior, the researchers meticulously picked off and counted the ticks on

their clothing and bodies. They also used an adhesive lint roller to pick

up ticks that might otherwise have escaped their attention. All told, they

found a total of 86 nymphal ticks on their bodies during the field trials.

 

 

" Activities that were riskiest involved considerable contact with wood, "

said Steinlein. " Of the six behaviors we analyzed, sitting still on leaf

litter was the least riskiest behavior, resulting in tick exposure only eight

percent of the time. "

 

 

Why the difference between wood products and leaf litter? The clue may be

in an important animal host for the larvae and nymphs of the western

black-legged tick.

 

 

" The western fence lizard is an important host for the ticks, and the

lizards often use logs in sunlit areas as basking sites, " said Lane. " Nymphal

ticks that are seeking hosts to feed upon may be going to the place where

they'll have the greatest chance of finding a lizard. Humans or pets that

happen to come along for a picnic lunch or a short rest on a log may be putting

themselves in harm's way. "

 

 

DNA tests revealed that 3 to 4 percent of the ticks the researchers found

on their bodies, as well as through drag sampling leaf litter with a white

flannel cloth, tested positive for B. burgdorferi and another, less

prevalent human disease-causing bacterium Anaplasma phagocytophilum. Estimates

from prior studies of ticks infected with B. burgdorferi in Mendocino County

are higher, ranging from 5 to 10 percent on average, with some spots

occasionally yielding rates of 15 percent or higher.

 

 

Tick infection rates normally are significantly higher in the northeastern

and upper midwestern United States, where most cases of Lyme disease

occur. Lane cautioned that the findings in this study are not intended to be

applicable to forested areas in other regions of the country.

 

 

But for people frequenting areas of California where Lyme disease is

endemic, the researchers recommend precautions to prevent tick exposure.

 

 

" I would avoid prolonged contact with wood as well as with leaf-litter

areas, and I would strongly suggest that people inspect themselves carefully

after spending time in tick-infested areas, " said Lane. " Moreover, I would

advise people to continue checking their skin for two to three days after

the potential exposure. Nymphal ticks are so hard to see in the beginning -

probably less than one in three people bitten by nymphs ever discovers the

tick that bit them. But they become easier to detect once they start swelling

up a bit after they've had a blood meal.

 

 

" Animal studies suggest that it usually takes longer than one day after

the tick becomes attached for the bacteria to be transmitted to the host, so

the sooner the tick is found and removed, the better, " said Lane.

 

 

The National Institutes of Health and the U.S. Centers for Disease Control

and Prevention helped support this research.

 

 

Related

 

Chipmunks And Shrews, Not Just Mice, Harbor Lyme Disease

The paper demonstrates that chipmunks and two shrew species, not just

mice, are the four species that account for major outbreaks. According to the

study, white-footed mice account for about a quarter of infected ticks.

Short-tailed shrews and masked shrews were responsible for a quarter each and

chipmunks for as much as 13 percent. Deer, a popular culprit of the Lyme

disease epidemic, play a rather minor role in transmitting the bacteria to

feeding ticks, although they are a major cause of the elevated tick densities

that are important for the spread of the disease to humans. Emerging

zoonotic pathogens, the 132 infectious diseases that cross the line between

animal and human species, like Lyme disease, are a constant threat to world

health.

_http://www.sciencedaily.com/releases/2007/11/071129183745.htm_

(http://www.sciencedaily.com/releases/2007/11/071129183745.htm)