Re: Forget the Deer?

From: A_Weisman (a_weisman_at_yahoo.com)
Date: 07/19/04 

Date: 19 Jul 2004 07:02:06 -0700

"Rita Stanley" <rlstanley@comcast.net> wrote in message news:<2uFKc.91710$WX.33596@attbi_s51>...
> http://www.nytimes.com/2004/07/18/opinion/opinionspecial/18WCameron.html
>
> The New York Times
> New York NYJuly 18, 2004
>
> WESTCHESTER
>
> Forget About the Deer
>
> By DANIEL CAMERON
>
> Mount Kisco - The Town of Greenburgh is so fed up with its abundance
> of deer
> that it has formed a committee to survey residents on their choice of
> shooting
> or poisoning them, or trapping and shipping them somewhere else. This is
> all
> well and good if you're trying to save shrubs and reduce motor vehicle
> accidents, two of the reasons cited for eliminating deer, but it won't
> help with
> another goal: lowering cases of Lyme disease, which have more than
> doubled
> nationwide during the 15 years that I have been treating the disease.
>
> Instead of blaming deer, we need to look at our own activities. Perhaps
> the most
> effective way to fight Lyme is to eliminate not deer, but a beloved
> fixture of
> suburban yards: the birdfeeder.
>
> The problem starts with a bug that should never have been called a deer
> tick.
> Its proper name is the black-legged tick.
>
> Deer aren't even carriers of Lyme
> disease; the main carrier is the white-footed mouse, while birds and
> rabbits also carry the disease. It's true that deer provide a blood meal
> to ticks that have been infected by white-footed mice and other
> carriers, but so do dogs,
> raccoons and striped skunks.
>
> The disease moves into suburban backyards in part because the infected
> ticks are attracted to birdfeeders, as are Lyme-carrying birds and small
> mammals.
>
> People who acquire the disease in their backyards aren't getting it just
> (or even
> mostly) from ticks on deer - all 27 species of birds in one Connecticut
> study
> carried the ticks that cause Lyme.
> Instead of fixating on the deer population, we should be looking at
> alternatives
> for combating Lyme and reducing our chances of developing this chronic
> disease.
>
> Getting rid of birdfeeders would help. DEET insect repellent, when used
> on
> clothes and shoes, can ward off 90 percent of the ticks. The American
> Academy ofPediatrics advises that DEET is safe for children if used
> sparingly and not applied to "a child's face, hands, or skin that is
> irritated or abraded."
>
> Spraying yards with the pesticides carbaryl and granular deltamethrin
> once or
> twice a year would eliminate up to 90 percent of the nymphal ticks.
> Pesticides
> should be used sparingly to protect other insects. And removing brush
> and leaf
> litter or creating a buffer zone of wood chips or gravel between forest
> and lawn
> or recreational areas can reduce the number of ticks by 50 percent to 90
> percent.
>
> Another focus of our attention should be how to treat this serious
> disease. I
> have witnessed the ravages of Lyme on countless occasions. I see
> patients who
> have been sick with Lyme disease for more than two years because a
> doctor would not treat them unless they had a positive laboratory test.
> I also have patients who have been sick for more than six months because
> they were never told that fatigue, poor memory, irritability and
> sleeplessness could be symptoms of
> neurologic Lyme disease. I have treated teenagers who were too sick to
> attend
> school and had to be tutored at home to finish their education.
>
> A National Institutes of Health trial found 107 chronic Lyme disease
> patients
> who were sick for more than four years.
>
> Quality of life was worse for them than
> for patients with diabetes and recent heart attacks.
>
> Yet as debilitating and fast-spreading as the disease is, doctors differ
> over
> how to diagnose and treat it. The Infectious Disease Society of America,
> for
> instance, recommends a one-time short-term treatment of 10 to 30 days.
>
> In contrast, the International Lyme and Associated Diseases Society
> guidelines
> on the prevention and management of chronic Lyme disease, of which I am
> the
> chief author, recommend more aggressive treatment for people at risk.
> Since the
> disease is chronic in up to half of patients treated for Lyme, these
> guidelines
> call for treatment of symptoms even when blood tests are negative for
> Lyme, and
> the early and prolonged use of antibiotics, including repeated courses
> should
> the disease recur. We still need lots of testing and research to find
> the best
> way to treat Lyme.
>
> For those who are frustrated with Lyme disease, forget about the deer.
> Killing
> them won't do the trick. Instead, lobby your local leaders for more
> financing on
> Lyme disease research and look in your own backyard.
>
> Daniel Cameron is a doctor in private practice.
> ****
> Letters to the Editor:
> email letters@nytimes.com or fax (212)556-3622.

>GregGerber@hotmail.com (Greg Gerber) wrote in Message-ID:
><146041df.0407190419.419a1045@posting.google.com>

>Ixodes scapularis must overwinter on a host to survive for the three
>stages --larval, nymphal, and adult-- of its two-year life cycle.
>Adult I. scapularis ticks are large and can overwinter (and mate) in
>large numbers only in an area with an abundance of large mammals or
>large birds. Birds fly and are migratory. Deer --the large mammalian
>hosts in most scenarios-- rarely wander more than a mile or so from
>the place where they were born. The white-tailed deer is indeed
>responsible for the survival and mating of I. scapularis adults in
>enough abundance to perpetuate an epidemic; without large mammals
like
>deer, I. scapularis adults could not survive the winter or give rise
>to the next generation of larval Ixodes ticks.

Overwinter on a host? Huh? ? ?

Where'd you get that?

Wow.

You always state things with such certainty. But this is just flat out
wrong.

Ticks are inactive in the winter (although can come out in
temperatures over 32 degrees). They sort of hibernate. They do NOT
spend time on hosts except when feeding. And in the first stage of
their lifecycle they don't spend it on a host at all. They are born
nymphs, uninfected and only become infected when they take their first
blood meal which is when they transform into the next stage of their
lifecycle.

There is Lyme in places where there are no deer.

And Dr Cameron is really just talking about other effective ways to
cut down on transmission to humans.

Read the info below. If someone doesn't like that the sites are the
ALDF and CDC well find any site on deer tick ecology. Those are the
first two with a good explanation I saw. We're not talking about
diagnosis and treatment.

And if you want to see the images, go to the websites.

===============================================================================
 American Lyme Disease Foundation - Deer Tick Ecology
http://www.aldf.com/DeerTickEcology.asp

DEER TICK ECOLOGY

What is a tick?

Ticks are not insects but Arachnids, a class of Arthropods, which also
includes mites, spiders and scorpions. They are divided into two
groups - hard bodied and soft bodied - both of which are capable of
transmitting diseases in the United States.

Ticks are parasites that feed by latching on to an animal host,
imbedding their mouthparts into the host's skin and sucking its blood.
This method of feeding makes ticks the perfect vectors (organisms that
harbor and transmit disease) for a variety of pathogenic agents. Ticks
are responsible for at least 9 different known diseases in humans in
the U.S., including Lyme disease, Rocky Mountain spotted fever,
babesiosis, and more recently, ehrlichiosis.

The Deer Tick Life Cycle

The deer (or black-legged) tick in the East and the related western
black-legged tick are the primary (and possibly the only) known
transmitters of true Lyme disease in the United States. Both are
hard-bodied ticks with a two-year life cycle. Like all species of
ticks, deer ticks and their relatives require a blood meal to progress
to each successive stage in their life cycles.

The life cycle of the deer tick comprises three growth stages: the
larva, nymph and adult. In both the northeastern and mid-western U.S.,
where Lyme disease has become prevalent, it takes about two years for
the tick to hatch from the egg, go through all three stages,
reproduce, and then die. A detailed description of this life cycle and
the seasonal timing of peak activity, as they occur in these regions,
is provided below.

Stage 1: Larva - As shown in the upper left corner of the life-cycle
diagram above, eggs laid by an adult female deer tick in the spring
hatch into larvae later in the summer. These larvae reach their peak
activity in August. No bigger than a newsprinted period, a larva will
wait on the ground until a small mammal or bird brushes up against it.
The larva then attaches itself to its host, begins feeding, and over a
few days, engorges (swells up) with blood.

If the host is already infected with the Lyme disease spirochete (a
form of bacterium) from previous tick bites, the larva will likely
become infected as well. In this way, infected hosts in the wild
(primarily white-footed mice, which exist in large numbers in
Lyme-endemic areas of the northeast and upper mid-west) serve as
spirochete reservoirs, infecting ticks that feed upon them. Other
mammals and ground-feeding birds may also serve as reservoirs.

Because deer tick larvae are not born infected, they cannot transmit
Lyme disease to their human hosts. Instead, "reservoir" hosts, as
mentioned above, can infect the larvae. Having already fed, an
infected larva will not seek another host, human or otherwise, until
after it reaches the next stage in its life cycle. Therefore, larvae
do not, in themselves, pose a threat to humans or their pets.

Stage 2: Nymph - Most larvae, after feeding, drop off their hosts and
molt, or transform, into nymphs in the fall. The nymphs remain
inactive throughout the winter and early spring.

In May, nymphal activity begins. Host-seeking nymphs wait on
vegetation near the ground for a small mammal or bird to approach. The
nymph will then latch on to its host and feed for 4 or 5 days,
engorging with blood and swelling to many times its original size. If
previously infected during its larval stage, the nymph may transmit
the Lyme disease spirochete to its host. If not previously infected,
the nymph may become infected if its host carries the Lyme disease
spirochete from previous infectious tick bites. In highly endemic
areas of the northeast, 25% of nymphs have been found to harbor the
Lyme disease spirochete.

Too often, humans are the hosts that come into contact with infected
nymphs during their peak spring activity (late May through July).
Although the nymphs' preferred hosts are small mammals and birds,
humans and their pets are suitable substitutes. Because nymphs are
about the size of a poppy seed, they often go unnoticed until fully
engorged, and are therefore responsible for the majority of human Lyme
disease cases.

Stage 3: Adult - Once engorged, the nymph drops off its host into the
leaf litter and molts into an adult. These adults actively seek new
hosts throughout the fall, waiting up to 3 feet above the ground on
stalks of grass or leaf tips to latch onto deer (its preferred host)
or other larger mammals (including humans, dogs, cats, horses, and
other domestic animals). Peak activity for adult deer ticks occurs in
late October and early November. Of adults sampled in highly endemic
areas of the northeast, 50% have been found to carry the Lyme disease
spirochete.

Adult deer tick questing for a host. Note the upper legs are raised in
preparation for latching on to a passing animal.

Adult deer tick seeking a suitable spot to feed.

As winter closes in, adult ticks unsuccessful in finding hosts take
cover under leaf litter or other surface vegetation, becoming inactive
in temperatures below 40 degrees F. Generally, winters in the
northeast and upper mid-west are cold enough to keep adult ticks at
bay until late February or early March (an exception was the warm
winter of 1997-1998) when temperatures begin to rise. At this time,
they resume the quest for hosts in a last-ditch effort to obtain a
blood meal allowing them to mate and reproduce. This second activity
peak typically occurs in March and early April.

Adult female ticks that attach to deer, whether in the fall or spring,
feed for approximately one week. Males feed only intermittently.
Mating may take place on or off the host, and is required for the
female's successful completion of the blood meal. The females then
drop off the host, become gravid, lay their eggs underneath leaf
litter in early spring, and die. Each female lays approximately 3,000
eggs. The eggs hatch later in the summer, beginning the two-year cycle
anew.

For residents of regions other than the northeast and upper mid-west:
Please note that where the range of the deer tick (or its close
relative the western black-legged tick) extends beyond the northeast
or upper mid-west, the timing of peak activity for each life stage of
the tick may differ from that described above. In these areas,
information on peak nymphal and adult tick activity can probably be
obtained from local universities and health departments.

============================================================================

Vector Ecology

Lyme disease is spread by the bite of ticks of the genus Ixodes that
are infected with Borrelia burgdorferi. For Lyme disease to exist in
an area, at least three closely interrelated elements must be present
in nature: (1) the Lyme disease bacteria B. burgdorferi (2) Ixodes
ticks that can transmit the bacteria, and (3) mammals such as mice and
deer to provide a blood meal for the ticks through their various life
stages.

 
Picture of the type of forested area that could be a habitat for
ticks.
 
 
Tick Habitat: In the United States, ticks of the genus Ixodes serve as
the competent vectors for transmitting the Lyme disease bacteria, B.
burgdorferi to humans. Ixodes ticks can be found in temperate regions
with high relative humidity at ground level. Known as the deer tick or
black-legged tick, Ixodes scapularis is responsible for transmitting
bacteria to humans in the northeastern and north-central United
States. In eastern states, ticks are associated with deciduous forest
and habitat containing leaf litter. Leaf litter provides a moist cover
from wind, snow, and other elements. Importantly, research
demonstrates that tick populations are reduced 72-100% when leaf
litter is removed. In the north-central states, I. scapularis is
generally found in heavily wooded areas often surrounded by broad
tracts of land cleared for agriculture. On the Pacific Coast, the
bacteria are transmitted to humans by the western black-legged tick
(Ixodes pacificus) and habitats are more diverse. Here, ticks have
been collected in habitats with forest, north coastal scrub, high
brush, and open grasslands. Coastal tick populations thrive in areas
of high rainfall, but ticks are also found at inland locations.

Life cycle of the deer tick: Knowing the complex life cycle of Ixodes
ticks is important in understanding the risk of acquiring Lyme disease
and in finding ways to reduce this risk. For this example, we will
describe the two year life cycle of an I. scapularis deer tick located
in a northeastern state. Life cycles may vary slightly for other ticks
located in different regions of North America.

Image presented by authority from the American Lyme Disease
Foundation.
 
The life cycle requires 2 years to complete. Adult female ticks lay
eggs on the ground in early spring. By summer, eggs hatch into larvae.
Larvae feed on mice, other small mammals, deer, and birds in the late
summer and early fall, molt into nymphs, and then are dormant
(inactive) until the next spring. Nymphs feed on rodents, small
mammals, birds and humans in the late spring and summer and molt into
adults in the fall. In the fall and early spring, adult ticks feed and
mate on large mammals (especially deer) and bite humans. The adult
female ticks then drop off these animals and lay eggs in spring,
completing a 2-year life cycle.

Picture of some natural sources of blood meals for Lyme disease ticks
(e.g., deer, dogs, birds, mice).
 
Natural reservoirs for Borrelia burgdorferi: Ticks, small rodents, and
other non-human vertebrate animals all serve as natural reservoirs for
B. burgdorferi. This means that the Lyme disease bacteria can live and
grow within these hosts without causing them to die. Larvae and nymph
ticks typically become infected with the Lyme disease spirochete, B.
burgdorferi, when they feed on small animals that carry the bacteria
in spring and summer. The bacteria remain in a tick as it changes from
larva to nymph or from nymph to adult in late summer or early fall.
Infected nymphs bite and transmit B. burgdorferi bacteria to other
small rodents, mammals, and humans, all in the course of their normal
feeding behavior.

>From left to right: The deer tick (Ixodes scapularis) adult female,
adult male, nymph, and larva on a centimeter scale.
(View enlarged image.)

Transmission to Humans: Research in the eastern United States has
indicated that, for the most part, nymphal ticks transmit Lyme disease
bacteria to humans from May to July. Feeding nymphs are rarely noticed
because of their small size, and thus have ample time to feed on
humans. Tick-to-human transmission of the Lyme disease bacteria
usually occurs after approximately 2 or more days of feeding. Although
tick larvae are smaller than nymphs, they rarely, if ever, carry B.
burgdorferi at the time of feeding and are not important in the
transmission of Lyme disease to humans. Adult ticks can transmit the
disease, but since they are larger and more likely to be removed from
a person's body within a few hours, they are less likely than nymphs
to have sufficient time to transmit the infection. As expected, few
cases of Lyme disease are reported in the cooler months of the year,
when adult Ixodes ticks are most active.
 
National Lyme disease risk map with four categories of risk.
(View enlarged image.)
 
Ticks search for host animals from the tips of grasses, shrubs, and
leaf litter and transfer to animals or persons that brush against
vegetation. They only crawl, not fly or jump. Ticks can attach to any
part of the human body but often crawl to the more hidden areas to
feed such as the groin or armpit and often where clothing is tight.
They feed on blood by inserting their mouths into the skin of a host
animal. Their bodies slowly enlarge with blood as they feed over
several days.

Picture of people enjoying the outdoors in a spot where risk of
exposure to ticks may be greatest.
 
Campers, hikers, outdoor workers, and others who frequent wooded,
brushy, and grassy places are commonly exposed to ticks, and this may
be important in the transmission of Lyme disease in some areas.
Because new homes are often built in wooded areas, transmission of
Lyme disease near homes has become an important problem in some areas
of the United States. The risk of exposure to ticks is greatest in the
woods and garden fringe areas of properties, but ticks may also be
carried into lawns and gardens by animals.

There is no evidence that a person can get Lyme disease from the air,
food or water, from sexual contact, or by handling wild or domestic
animals. There is no convincing evidence that Lyme disease can be
transmitted by insects such as mosquitoes, flies, or fleas. Lyme
disease infection from a blood transfusion or other contact with
infected blood or urine has never been documented.

United States map of reported cases: Lyme disease cases have been
reported by 49 states and the District of Columbia. Cases remain
concentrated in the northeastern, north-central, and Pacific coastal
regions. Another approach to understanding the distribution of Lyme
disease is to examine where the tick vectors are present. Not
surprisingly, areas with black-legged ticks report the highest
incidence of Lyme cases, and studying the tick distribution can also
highlight areas of potential risk.
The map at right is based on a comprehensive review of the literature
in the United States regarding established and reported distribution
of the Lyme disease vectors Ixodes scapularis and Ixodes pacificus.
Data compiled from the literature review are presented by county.
"Established" means at least six ticks or two life stages (larvae,
nymphs, adults) were identified in the county. Note that the principal
vectors are Ixodes scapularis in the northeast and upper-Midwest
states and Ixodes pacificus along the West Coast of the United States.
Although I. scapularis is widely distributed in the southern U.S., it
is not an established vector of Lyme disease to humans in that area.
This map is useful in helping the public and health authorities assess
the relative importance of Lyme disease in their area.

Relevant Pages