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Lymes, Rocky Mountain Spotted Fever, Ehrlichia
By Dr. Kathleen Connor, DVM
The tick season is here and so is tick disease season. This is a subject near and dear to my heart as my current Wilderness Search and Rescue dog was severely affected by Rocky Mountain Spotted Fever (RMSF) last summer. Here is an overview of the three main tick borne diseases: Lyme Disease, Rocky Mountain Spotted Fever, and Ehrlichia and steps on how to protect your Lab during tick season.
The tick season is fast upon us and so is the tick disease
season. This is a subject near to my
heart as my current Wilderness Search and Rescue dog was severely affected by Rocky
Mountain Spotted Fever (RMSF) last summer.
Here is an overview of the three main tick borne diseases: Lyme Disease, Rocky Mountain Spotted Fever,
and Ehrlichia.
Lyme Disease
Lyme disease seems to be the most common of all the tick
diseases. In my practice in Virginia,
about one-third of all the dogs tested are positive for Lyme disease. The most common clinical signs of an active
Lyme infection are fever, decreased appetite and multiple swollen and painful
joints. Interestingly, when a dog
develops an acute infection, the joints that are most often affected are the
ones closest to the tick bite. However,
the lameness associated with Lyme disease can also be sporadic, and can
alternate from one limb to another.
These clinical signs can take 2-5 months to develop after an infected
tick bites your dog. The infection can
become subclinical and no clinical signs are evident. There is also a rare and
nearly always fatal form of Lyme disease that attacks the kidneys. An interesting study showed that Labrador
and Golden Retrievers were five times more likely to develop the kidney form of
the disease than the general canine population.
Lyme disease is transmitted by the deer or black legged tick
with the deer mouse being the reservoir of the disease. These ticks are found in nearly every
state. At this time, the disease is
most prevalent in the east and north east and it’s been shown that more than 50%
of adult deer ticks in this area carry Borrelia burgdorferi, the causative
agent of Lyme disease. The good news is
that it takes 24-48 hours after the tick becomes attached for B. burgdorferi to
be transferred from the tick to the dog.
Rocky Mountain
Spotted Fever
Rocky Mountain Spotted Fever (RMSF) is not as common as Lyme
disease, but it usually causes a more significant illness and is more likely to
be fatal. Eight to ten days after the
bite of an infected tick clinical signs develop. Some of the clinical signs can mimic Lyme disease such as fever
(up to 105°F), decreased appetite and generalized pain. In severe cases though, bleeding disorders
causing unexplained bruising on the gums and in the skin and neurological signs
such as in-coordination, head tilt and seizures can develop. My dog started
with a fever, decreased appetite and generalized pain, but very quickly
progressed to the neurological signs even while he was on antibiotics. It takes
five to ten days after the bite of an infected tick for clinical signs to
develop.
RMSF is transmitted by the American dog tick. These can be easily identified by the white
saddle just behind the mouth parts.
Again, these ticks are found just about everywhere. The good news is only 1-3% of ticks carry
the disease causing organism. As with
Lyme’s disease it takes an extended time after the tick attaches before
transfer of the disease causing organism occurs, usually 6-20 hours.
Ehrlichia
Ehrlichia is another tick borne disease that can mimic other
diseases and be hard to diagnose. There
are several species of Ehrlichia that can cause disease: Ehrlichia canis, Ehrlichia
chaffeensis, Ehrlichia ewingii,
Ehrlichia equi, and Ehrlichia platys. The clinical
signs of the acute phase are very vague:
fever, lethargy, decreased appetite, and enlarged lymph nodes. After the bite of an infected tick, it takes
one to three weeks for clinical signs to develop and then the signs may last
only a week or two. The dog may then
mount an immune response and clear the disease or it may subside into a sub
clinical or chronic form. Again, the
signs of a chronic infection are vague: weak, thin dog with no appetite and
pale mucus membranes. In the chronic
stage the bone marrow wears out and the dog develops a pancytopenia, meaning
that there are no red blood cells, no white blood cells and no platelets being
produced. Once this chronic stage is
reached, prognosis is very guarded. An
interesting fact: German Shepherds are more likely to develop the chronic form.
Ehrlichia is transmitted by several different kinds of
ticks, the main vector being the brown dog tick and the other, minor vector being
the Lone star tick. The brown dog tick
is found in every state of the contiguous United States and the Lone star tick
is found in the southeast. Most cases
of ehrlichia are diagnosed in the spring and summer months when the ticks are
most active.
Diagnosis
It can be very difficult to unequivocally diagnose a tick
disease because there are so many variables that affect the course of the
disease: age of the dog, health of the dog and the ability of the dog’s immune
system to mount a response are just a few.
Sometimes it is very easy to diagnose- young active dog that hikes,
suddenly shifting leg lameness with high fever makes me think of tick
disease. But, this also mimics trauma,
early hip or elbow dysplasia, OCD and panosteitis.
You should think of four things when considering a tick
borne disease:
1. History of exposure to ticks
2. Clinical signs typical for the disease
3. Specific antibodies to the individual
disease
4. Good response to the antibiotic treatment
Let me explain a little about tick titers, because they can
be very confusing. Titers in general, measure the antibody response to a
disease. Most veterinarians have an in-house test for Ehrlichia canis only and
Lyme. This is a very good screening
test, but there is no quantitative value and in order to know if there is an
active disease process you need to know what the titer is to the individual
disease. The titer is given as a ratio: 1:64, 1:128, etc. If your dog is in the early stage of the infection, the titer may
actually show no exposure (<1:20) or a very low exposure (1:64 or 1:128). If there are clinical signs evident that
scream tick disease and the titer for your dog shows no exposure, it just means
that the immune system hasn’t had a chance to mount a measurable response. Take a titer 2-4 weeks later and the titer
should be at least four times greater than the original level.
My dog had a titer at the beginning of his bout with RMSF of
1:1024; that level, his clinical signs, and his response to doxycycline
unequivocally said that he was suffering from RMSF. On a whim, 3 months later, I decided to recheck his RMSF titer. At that time it was 1:8192. He wasn’t still suffering from the disease,
but his immune system had mounted one heck of a response. Interestingly, his titer for Lyme’s remained
positive, but levels stayed the same (1:256) which probably meant that he’d
been exposed and developed an immune response to control the infection. One thing to keep in mind, don’t wait for
the paired titer to be run, start treating for the tick disease right away if
the suspicion for it is high. Doxycycline
is inexpensive with relatively few side effects, but the tick diseases are
horribly debilitating and can cause long term effects if not treated early.
It is when these diseases become chronic that they can be
very hard to diagnose. Titers don’t
usually change dramatically as they do when in the active stage, so a rising titer
can’t always be helpful for the diagnosis.
You need to work closely with your veterinarian to help figure out if a
chronic tick disease is the problem.
Treatment
Treatment of choice for all tick diseases is doxycycline,
daily for at least 4 weeks. Most of the
agents that cause these problems are slow growing and it takes this long for
the antibiotic to be effective. If the
dog is very sick from the disease, hospitalization is needed, but most can be
treated on an out-patient basis. The
response to doxycycline is startling.
Most times the dog will appear completely normal 24 hours after starting
the medication.
Prevention
The only way to truly prevent these diseases is to kill the
tick before it attaches. The good thing
is that it takes many hours and sometimes days after attachment for the tick to
transmit the disease. So, they need to
be killed before that happens. The only
products that I know for sure that repels ticks before they attach are: the
Preventic™ collar and Advantix™. The
main draw back with the Preventic™ collar is it can’t get wet or its effectiveness
is severely reduced. Another
significant problem is that it is extremely toxic if the dog happens to get the
collar off and chews on it. Advantix™
is relatively new and according to the manufacturer, will actually repel the
ticks and kill them before they can attach. It is supposed to repel mosquitoes
as well and is water resistant. Frontline™ is another product that I recommend
to my clients, it doesn’t repel the ticks, but it does eventually kill
them. It too, is water resistant. There
is currently a Lyme disease vaccine available for dogs. However, there are
varying opinions on its effectiveness. Your veterinarian can tell you if this
precaution is a good idea for your area.
Do a thorough tick check each night, after working your dog
in tick habitats. That is most likely
going to be the best way to prevent that nasty arthropod from attaching and
making your partner sick.
How to Remove a Tick
Because it takes roughly 24-48 hours for a tick to transmit
bacteria, it is important to remove ticks from your pet’s skin as soon as you
discover them. Do not attempt to
remove the tick by touching it with a burnt match or swabbing it with alcohol
or petroleum jelly. This will only aggravate the tick and cause it to release
more bacteria into the blood. Do not kill the tick before it has been removed.
- Use
either a tick removing device or a pair of fine-tipped tweezers.
- Do not
squeeze the ticks body, but rather, grasp the mouthparts of the tick as
close to the skin as possible.
- Pull
the tick straight out with a firm and steady force until it releases its
hold. Do not twist the tick as you are pulling.
- The
barbed mouth of a tick will not let go easily, so take your time and be
patient- you want to get the whole tick.
- If it
is a female tick, there will be eggs inside, so you want to get rid of
them in a safe manner. This can be achieved by placing the tick in a jar
of rubbing alcohol. (Your veterinarian may also want to identify it.)
Ticks are not killed by flushing them down the toilet. Please do not
squash the tick with your fingers. The contents of the tick can transmit
disease.
- Wash
the area of the bite thoroughly with soap and water. You may also want to,
apply a small amount of a triple antibiotic ointment.
- Watch the bite for signs of inflammation. It is not uncommon for a welt and skin reaction to occur. The swelling is due to toxic tick saliva.
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