|The adult tick
seeks a larger host, hence its name the deer tick; however, with man
encroaching upon the range of the deer, there are often plenty of dogs or humans for the
tick to attack. The adult ticks mate on their new host, feed, and transmit the Lyme
spirochete if they are carrying it. The male tick remains attached through the winter but
the female, once engorged with the hosts blood, drops off, hides under leaves and
other debris through the winter, and lays her eggs in the spring for the two-year cycle to
The feeding tick is basically a
blood-sucker. It must keep its hosts blood from clotting in order to continue
sucking so it is able to regurgitate assorted enzymes to keep the blood flow liquid and
smooth. It is during this regurgitation process that the Lyme spirochete is brought up
from the ticks mid-gut to its mouth parts.
This process requires a minimum of 48 hours which means
that if the tick is removed within 48 hours of attachment,
the spirochete cannot be transmitted and the host will not get the disease.
Tick control on the host is an effective means of infection
prevention. There are several effective tick control products available including: the
Preventic® collar, Advantix®, Frontline®,
Vectra 3D® and Promeris Canine®. All of these products either kill the
tick or cause it to drop off prior to the 48 hour deadline.
On the west coast of the United States, there is far less
Lyme disease than in the east, although the northern coast of California is considered to
have moderate risk. This is because the Lyme vector in these areas is primarily Oxides
pacificus, a tick that strongly prefers to feed on reptiles rather than mammals.
Reptile blood has natural anti-Borrelia factors which kill the Lyme spirochete and
prevent further transmission.
The CDC (Center for Disease Control) provides a map, below,
of the U.S. indicating risk.
There are several subspecies of Borrelia burgdorferi
in different parts of the world so Lyme disease is not unique to the United
The spirochete that causes Lyme disease cannot live outside
the body of a host. It must live within either a mammal or a tick.
In the mammals body, the spirochete is especially
adept at binding to connective tissue. If one is doing additional reading on this
organism, one will encounter references to the spirochetes surface proteins called
Osps (Osp stands for outer surface protein).
Different Osps are expressed depending on whether the spirochete is attached to the
tick midgut (OspA), the mammals connective tissue (OspC), or whether the tick is in
an early or late stage of mammal infection (Osps E and F respectively). By modifying its
Osps, the spirochete is able to change its presentation to the mammalian hosts
immune system thus escaping immune destruction. In addition to changing Osps, the
spirochete can change its shape into at least 3 different forms and is able to hide within
cellular folds. (The Lyme spirochete is a master of disguise and camouflage.)
This presents an enormous diagnostic challenge:
if the hosts immune system cant even find the organism,
how are we supposed to detect it?
A dog with symptoms of Lyme disease ideally should have a
test to confirm or rule out Lyme disease. Since it is almost impossible to culture
the Lyme spirochete, efforts have centered on detection of antibodies against the
Osps. Here are the problems encountered with this method:
|In a Lyme endemic area, as many as 90% of the dogs will have
antibodies against the Lyme spirochete. Most exposed dogs never get sick but almost all of
them will develop antibodies and these antibodies persist for years. How do we tell the
dogs that have active infection from those that have been exposed and are not sick from
|Vaccine has been available for Lyme disease for a decade or
more. How do we distinguish antibodies generated by the vaccine from those generate by
|How do we distinguish antibodies generated by similar
organisms (Leptospira, for example, or harmless other Borrelia species)?|
The solution to these problems has come about only
recently in the form of the C6 test. This is an immunological test for
antibody against the C6 peptide, a very unique section of the one of the Borrelia
burgdorgeri surface antigens. As the spirochete changes its configuration to escape
the hosts immune system, the C6 peptide remains constant and always detectable.
Vaccine does not contain the C6 peptide so vaccinated dogs will not test
positive. Dogs with other infections will not erroneously test positive. Further,
this test is simple enough to be available as an in-house test kit (the IDEXX Snap-3
Dx test or Snap-4 Dx test) which can be run in most veterinary
hospitals, with results in approximately 10 minutes.
This still does not address distinguishing active infection
from exposure. Dogs will test C6 positive within 3-5 weeks of infection. They stay
positive for over a year.
Which of these dogs get sick and which ones do not? Does the
dog with joint pain, fever, and a positive C6 test need medication? This is where the news
is particularly good.
Treatment of Lyme disease utilizes a 2-4 week course of
doxycycline a medication which is inexpensive and has limited side effects potential.
Amoxicillin is another effective alternative, also inexpensive and with minimal side
effects. If Lyme disease is a consideration, many veterinarians simply prescribe the
medication. Obvious improvement is seen within 48 hours. Further, most tick-borne
infections capable of causing joint pain, fever, and signs similar to Lyme disease
generally all share doxycycline responsiveness so a simple course of medication actually
covers several types of infection.
Eradication of the Lyme spirochete is not a reasonable
expectation with treatment; the organism is simply too good at hiding. The goal instead is
to bring the patient into what is called a premunitive state. This is the
state that 90% of infected dogs achieve when they get infected but never get ill: the
organism is in their bodies latently but is not causing active infection.
Some dogs are in fact harmed by the long time presence of an
infectious organism in their bodies. The immune system is constantly active in its
attempt to remove the invading spirochete and over the years these complexes of antibodies
may deposit in the kidney and cause damage. It has been recommended that dogs with
positive Borrelia burgdorferi antibody levels be regularly screened for significant
protein loss in their urine with a test called a urine protein to creatinine
ratio. This group of dogs may require medication for their kidney disease.
Recently an especially sensitive test has been developed for
the detection of minute quantities of blood proteins in the urine. This test, called the
Erd test, is so sensitive that its use is not yet determined (i.e. at what point is
albumin loss in the kidney significant and under what circumstances might some albumin
loss be normal and expected?).
Vaccine prevents infection in dogs vaccinated before any
exposure to Lyme spirochetes. This means it is only helpful for dogs not yet exposed such
as puppies and dogs from non-endemic areas travelling to endemic areas. Annual boosters
continue the vaccine-based immunity.
There are two types of vaccine available: the killed whole
spirochete vaccine (Fort Dodges vaccine) where basically intact dead spirochetes are
injected into the host. By using the entire spirochete, the host is exposed to parts of
the organism that are not useful in immunization and may lead to vaccine reaction. The
other type of vaccine is felt to be superior in preventive reactions and that is the
recombinant vaccine (Merials vaccine). This vaccine generates antibodies
specifically against OspA, the surface protein the spirochete uses to attach to its tick
host. When the tick bites and sucks blood full of Anti-OspA antibodies, the
spirochetes migration sequence is blocked and the spirochete is prevented from even
exiting the tick. The vaccine utilizes DNA for OspA cloned into a harmless virus so that
the entire Lyme spirochete is not used; only the OspA DNA is used.
Vaccination against the Lyme organism remains controversial.
We will present both sides of the argument and the pet owner can decide if they want to
include vaccination in their Lyme prevention efforts.
Argument Against Vaccination
|Lyme disease in the dog is an infection for which over 90% of
infected dogs will never get sick and the 5-10% that do get sick can be easily treated
with a safe inexpensive course of antibiotics. This situation would seem to indicate that
vaccination is simply not worth the expense.|
|As for the kidney disease that can occur in some individuals
with long term antigen exposure: we do not know what Borrelia antigens are involved
in the immune stimulation that causes this condition. It might be that the same antigens
used in the vaccines are involved in which case vaccination might be just as hazardous as
actual infection. Even OspA, the same antigen of the recombinant vaccine, has been
implicated in chronic human disease. |
Argument For Vaccination
|We vaccinate ourselves for the flu, an infection that is for
most people more of a nuisance than a|
life-threatening event, and think nothing of it. Vaccination is about prevention of
infection; just because an illness is not life-threatening does not mean that we should
not prevent it with vaccine. Further, in a
non-endemic area, Lyme disease is not going to be a cause of arthritis that most
veterinarians will consider. Treatment is only simple if one thinks to perform the
treatment but in an area where there is very little Lyme disease, this treatment may
easily be omitted. Why not just prevent the infection outright from the beginning if the
dog is going to travel to a tick endemic area?
|If we allow our dogs to readily become infected with the Lyme
organism, do they not become a potential source for human infection (through their ticks)?
We try to minimize the deer and mice in our vicinity but we want to keep company with the
family dog but who wants a reservoir of Lyme spirochete in their home?|
|As for the kidney disease, we do not know what spirochete
antigens are implicated in this condition. The recombinant vaccine exposes the
patient only to one spirochete antigen (OspA) and prevents the introduction of the
spirochete into the mammals body. Vaccination, at least with the recombinant
vaccine, may be preventive to this syndrome. |
Again, when it comes to prevention, there is nothing
controversial about tick control.
It is crucial in Lyme endemic areas to use tick controlling products.
Lyme disease is a regional problem. For more guidance
regarding this infection in your area or areas where you will be travelling, see your