Tracking Lyme Disease in Dogs May Help Protect
WEDNESDAY, Aug. 10 (HealthDay News) -- Tracking Lyme disease
infections in dogs may help scientists predict possible outbreaks
of the tick-borne illness in humans, government researchers
Since dogs are also susceptible to Lyme disease, they can be a
good indicator of the risk of human infection, the scientists from
the U.S. Centers for Disease Control and Prevention said. When
blood tests show that few dogs in a given area carry the bacteria,
the risk to people is relatively low, they noted. Conversely, when
more dogs test positive for Lyme, people may be at increased risk,
"Public health authorities could use this to assess and evaluate changes in their region," said Dr. Gary P. Wormser, chief of infectious diseases at New York Medical College and Westchester Medical Center in Valhalla. "This could be of help in understanding the risk areas for humans."
The report, released Aug. 10, is published in the September
issue of the CDC journal
Emerging Infectious Diseases.
For the study, a team led by Dr. Paul Mead, a CDC medical
epidemiologist, used data from 46 states on human and canine Lyme
Comparing the data, Mead's team found that when 1 percent or
less of the dogs tested positive for Lyme disease, the risk of
people becoming infected was low. However, when more than 5 percent
of the dogs were infected, the risk to people was high.
A 5 percent (or higher) rate of positive blood test results in
dogs "can be a sensitive but nonspecific marker of increased risk
for human Lyme disease," the researchers wrote in a CDC news
release. "Because dogs do not transmit infection directly to humans
[or humans to dogs], this association reflects similar
susceptibilities to tick-borne infection."
Sometimes, this level of canine infection "appears to anticipate
increasing rates of human infection at the county level.
Conversely, canine [prevalence of 1 percent or less] is associated
with little to no local risk for human infection," Mead's group
Blood tests can detect a dog's exposure to the bacteria, even
when no symptoms appear. "Most of the time the dogs appear to be
asymptomatic, but they do develop clinical disease as well,"
Wormser said. As a result, they may develop problems walking and
possibly heart or kidney complications.
Like humans, dogs with the disease can be treated with
antibiotics. "There is also a vaccine for dogs," Wormser said.
Symptoms may abate without treatment, but Lyme disease can leave
Commenting on the study, Phillip J. Baker, executive director of
the American Lyme Disease Foundation, said, "You have to wonder if
a dog is a good sentinel animal."
Their travel history and the use of tick repellent can affect
estimates of Lyme disease prevalence in a specific area, he
To prevent being bitten by the deer tick, which spreads Lyme
disease, Baker advises checking your pet (and yourself) after
walking through woods, fields or tall grass. Many dog owners also
use tick repellent on their pets, he said.
Areas where cattle and goats are raised may have a reduced risk
of Lyme disease, according to another study in the same journal
Researchers from Charite Universitatsmedizin Berlin in Germany
found pastures containing livestock bore fewer ticks in general and
fewer ticks carrying Lyme disease. Hikers passing through these
pastures were 40 to 54 times less likely to contract Lyme disease
than those walking through meadows or fallow land, they said.
It's possible that grazing animals reduce the tick's habitat or
perhaps the ticks shed the Lyme disease bacteria when they feed on
animals, the researchers said.
"Extensive landscape management that uses domestic ruminants not only serves to maintain cultural and natural heritage in Germany but also seems to confer a health benefit for hikers and others seeking recreation," the researchers wrote in the CDC news release.
For more on Lyme disease, visit the
U.S. National Library of Medicine.
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