Lyme Disease (LD)
is the number one tick-borne disease in North America. While it is
found in 48 states, it is most threatening to paddlers and other outdoor
enthusiasts in the northeast, from Massachusetts to Maryland, the
upper midwest in Wisconsin and Minnesota, and in California. The disease
is caused by the spirochete bacterium Borrelia burgdorferi, which
is carried by the western black-legged tick (Ixodes pacificus) on
the Pacific coast, and by the black-legged tick, commonly known as
the deer tick or bear tick (I. scapularis), in the upper midwest,
the northeast from Maryland to Maine and throughout Florida. Both
kinds of ticks live two years and pass through three life stages after
hatching from eggs. In early spring, newly hatched larvae ingest the
LD bacterium when they take their first blood meal on white-footed
mice. The larvae then molt into pinhead-sized nymphs that transfer
the disease to humans from late spring through mid-summer. In the
fall, although the adult ticks can still transmit LD, they are larger
and easier to see and remove, and are less likely to attach to passing
humans.
Ticks climb the branches and stems of low bushes and tall grasses
until they reach the tips of the leaves and blades of grass. There
they wait for unsuspecting paddlers to come thrashing through the
thickets on their way to the highest bluff or the most perfect place
to eat lunch or make camp. I once walked through a thicket on Cape
Cod, Massachusetts, and looked down to see an army of deer ticks marching
up my sleeves and pant legs. A friend of mine, Don Betts, told me
of a similar experience he had on an island in Narragansett Bay, Rhode
Island. We were lucky; we saw the ticks. Lyme disease has become prevalent
in areas where white-footed mice and large populations of white-tailed
deer live. A scientific study in Massachusetts found that, over seven
years, 35 percent of 190 residents living near a coastal refuge with
an abundant deer population had contracted LD. Among the residents
nearest the refuge, 66 percent had the disease.
Symptoms
The best early marker for LD is a red rash-like ring around the
site of the original bite, which can appear anywhere from three
days to a month after the bite has occurred. The ring starts small,
but then spreads outward to six inches or more in diameter with
a less inflamed center. Other early LD symptoms may include fatigue,
fever, headache, stiff neck, muscle and joint pain, inability to
concentrate. Unfortunately, nearly half of all LD victims do not
exhibit the bull's-eye rash. More than half of LD victims are unaware
that they have been bitten until symptoms appear weeks or months
later, but even then, they may think they have the flu. Advanced
cases of LD may result in severe arthritis, or cardiac, neurological
and other symptoms severe enough to require hospitalization. Some
victims have been diagnosed as having rheumatoid arthritis and other
diseases, only to find out later that it was advanced LD.
Treatment
LD has been hard to diagnose because laboratory tests have often
given either false-positive or false-negative results, which have
then been used as the basis for treatment decisions. If caught early,
LD is easily treated with antibiotics such as tetracycline. Doctors
in regions where LD is prevalent are now more willing to start antibiotic
treatment based on observed symptoms and circumstances instead of
basing their decision on the outcome of laboratory tests for LD.
(Using antibiotics to treat someone without LD is less serious than
failing to provide treatment when it really is LD.) Advanced LD
is very serious and very difficult to treat. Treatment of advanced
LD may require prolonged oral or even intravenous administration
of antibiotics. The debilitating effects of LD and the threat of
repeated annual cycles of infection and antibiotic treatment have
been powerful arguments for development of an LD vaccine. Note that
while doctors in the endemic areas keep on the lookout for LD, doctors
in inland regions who treat a patient who went paddling in one of
the endemic areas would be unlikely to look for LD.
Prevention
The best plan is to fastidiously avoid going into high grass and
brush. Wear light-colored, long-sleeved shirts and long pants that
can be tucked into your socks. The ticks are black or dark brown
and nymphs are the size of a pinhead or a period at the end of a
sentence. They are quite hard to see on dark clothing, so it helps
to wear light-colored clothing. Shoes and clothing may be sprayed
with either tick repellent DEET (diethyl-m-toluamide) or Permethrin,
but care should be taken not to spray directly on skin. Use a 30
to 35 percent DEET solution for adults and a maximum of 10 to 15
percent for children. DEET must not be used on babies. Be sure to
read and follow the directions on the product you purchase. The
instructions on a can of Permethrin state that you must spray the
clothing outdoors and then wait at least two hours before wearing
it. After a ramble in the brambles, both one's body and clothing
should be closely inspected for ticks. I have been bitten by ticks
that were hiding in pants or shirt seams I had put on again after
I thought the clothes were tick-free. Since then, clothes I wear
outdoors go into the wash before being worn again. The good news
is that if you find an imbedded tick and remove it within the first
24 hours, it will not infect you with its cargo of LD bacteria.
While the nymph-stage tick is the size of a pinhead, the adult is
about 1/16-inch long. When a tick feeds, the abdomen enlarges, and
it becomes much easier to see. Tick removal is not effectively done
with one's fingers. To remove a tick, use fine point tweezers to
grasp its head and gently pull it out. Do not squeeze the body of
the tick, cover it with petroleum jelly or burn it to try to remove
it.
Vaccine
There is good news on the tick front. Late last year, the FDA gave
final approval for commercial release of the first-ever vaccine
for LD. The new vaccine, LYMErix, by SmithKline Beecham, is approved
for persons 15 to 70 years of age. It is administered first when
LD is suspected and followed with another dose later, with a final
dose a year later. xAfter two doses it is 50 percent effective;
it reaches its maximum effectiveness-79 percent-after the third
dose. Thus, it won't make us safe this year, but those choosing
to use the new vaccine will be able to start the new millennium
with a high level of resistance to LD infection. How long such protection
will last is unknown at present. Trials are currently in progress
on children ages 4 and older. Observed side effects to the vaccine
include some redness and swelling around the injection site, flu-like
symptoms, and some joint and muscle pain. Side effects generally
disappear within three days. The viability of the vaccine is not
affected by whether or not the patient has been previously exposed
to LD. The series of three vaccine doses costs around $240, and
may be covered by some health plans in areas where LD is endemic.
Even if you elect to take the vaccine to prevent LD, you must still
make an effort to avoid being bitten by ticks, as they can also
carry human babesiosis (Babesia microti) or human granulocytic ehrlichiosis
(HGE). Studies have shown that ticks often carry combinations of
these diseases. HGE, also treated with antibiotics, develops more
rapidly than LD, and causes flu-like symptoms including fever, headache,
muscle aches, chills, nausea and vomiting. HGE can be life threatening
and must be treated promptly.
Charles A.
Sutherland Ph.D. is a medical writer, biochemist and coastal kayaker
on the east coast. He can be contacted at: skimmer@mail.enter.net
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Health
Lyme Disease: How to Avoid It 