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WHAT IS LYME DISEASE IN DOGS?

Learn About this tick-borne disease
by T. J. Dunn, Jr. DVM
http://www.thepetcenter.com		 talalogoa

What is Lyme Disease in dogs?  Transmitted through the bite of a tick, Borrelia burgdorferi is the scientific name of the bacteria that causes Lyme Disease.  These microscopic bacteria are a type called spirochete... they have a coiled or cork-screw lymedrs appearance under the microscope.  The disease is actually named after the townlymeixodesnymph1small in Connecticut where an early outbreak was first described... Lyme, Connecticut.  (Remember, ticks don't cause the disease, they merely harbor and transmit the bacteria that cause the disease.)  And being fussy little bacteria, not just any ol' genus of tick will do as a carrier.  At least three known species of ticks can transmit Lyme Disease.  However, the great majority of Lyme Disease transmissions are due to the bite of a very tiny tick commonly called the Deer Tick, or Black-legged Tick. See the image on the right.  Reference for the identification of this tick is at (http://creatures.ifas.ufl.edu/urban/medical/deer_tick.htm). Its scientific name is Ixodes (pronounced eye-zod-ease) scapularis.  Lyme Disease in dogs has been reported in every state but certain geographical areas are much more likely to harbor bacteria-carrying ticks than others.  To see close-up images of a different specie of tick (that does not usually transmit Lyme Disease) feeding on a dog, view here.
 
The tick's body size varies depending on the stage of its two-year life cycle.  I show my clients a life-sized photo of the tick whenever I diagnose a case of Lyme Disease because often the dog owners are skeptical about the presence of ticks... "It can't be Lyme Disease, Dr. Dunn.  This dog has not had a single tick all year.  I know because I've checked her every time she's come indoors."  Smaller than the head of a pin, these ticks are hard to see!  They don't glow in the dark.  They don't make the dog itch.  And they are very quiet about what they do.  Yes, cats do contract Lyme Disease but very uncommonly. The Ixodes tick is often called the deer tick because the adult stage of the tick prefers to feed on deer.  However, it will feed on other creatures such as skunks, birds, canines and people.  How do these ticks come to carry the Lyme Disease-producing bacteria in their tiny bodies?  (Take a look at the UPDATE at the end of this article, too).  Here's what happens:
Life Cycle:
lymeticks2small
This photo (click to enlarge) shows the AMERICAN DOG TICK (Dermacenter variablis) male and female on the left edge of a postage stamp.  Four Black-legged ticks (Ixodes scapularis) are displayed on the right edge of the stamp; they carry the bacteria that causes Lyme Disease. There is a female (largest tick) and male and two nymphal stages of the Black-legged tick.

Tiny rodents, such as voles, and especially the white-footed mouse, harbor in their bodies thousands of the Borrelia bacteria without getting sick.  In the early spring while the white-footed mouse goes about its business, some lucky Ixodes tick larvae (from newly hatched eggs laid late the previous fall) grab onto the mouse and begin to feed on its blood.  During this feast, the tick larvae acquire many bacteria from the mouse's fluids.  The bacteria think this is just great because they can survive and multiply in the tick's gut just as well as in the mouse's. And, what's even better from the bacteria's point of view, their huge numbers won't kill the tiny ticks either.  The bacteria have now gone from the host, a white-footed mouse, to the tick carrier called a vector, and are thriving - a bacterial reproductive bonanza!

When winter comes, the tick larvae lie dormant, dreaming of warm-blooded creatures upon which to dine come next spring.  Tick larvae like the little white-footed mouse but will settle for you or your dog.  The bacteria are doing fine too; they're just going along for the warm ride inside the little mouse.

Once the warmer spring temperatures arrive, the six-legged tick larvae matures into the eight-legged nymphal stage.  Later in the summer, the nymphs reaches the adult stage.   The young adult ticks, still harboring all those bacteria without ill effects, just happen to find themselves riding the legs of a white-tailed deer.  Banquet time!   After the ticks suck the deer's nutrient-rich blood, they can mate and produce thousands of eggs.  The following spring the eggs hatch into a new batch of larvae.
 
So where do you and your dog fit in this chain of bacteria, mouse, tick and deer?   Although the tick, during various stages of its life cycle, prefers certain creatures upon which to feed, it is quite willing to belly up to a table where people or dogs are the main course.  Regardless of the stage - larvae, nymph or adult Ixodes tick - if these critters carry the bacteria in their bodies, people and dogs can become infected if bitten.  Sometimes, but not always, clinical sickness (observable disease) results.

What percentage of Ixodes ticks carry the bacteria?  That varies according to regions.  Research has shown that in endemic areas of the mid-Atlantic and Northeast, nymphal-infected ticks ranged from 25 to 50 percent, and, in north central regions, 10 to 16 percent.  It is the tiny nymphal stage that is the most responsible for transmitting the disease.
lymeticksizes
There is no evidence that people can contract Lyme Disease directly from wild or domestic animals.   In other words, you can't catch Lyme Disease from your dog or from a deer.  But if infected urine or blood were to come in contact with an open wound, who knows?  And as time and evolution go on, variations of disease producing organisms can be a threat.
 
Signs of Lyme Disease in Dogs
lymepup Of the hundreds of cases of canine Lyme Disease that I have seen, over 90 percent of canine patients were admitted with signs of limping (usually one foreleg), lymph node swelling in the affected limb, and a temperature of 103 degrees (101 to 102.5 degrees is normal).  The limping usually progresses over three to four days from mild and barely noticeable to complete disuse of the painful leg.  Once the dog starts to be affected by the bacteria, Lyme Disease can progress from alymeixodesnymph2small mild discomfort to the stage where a dog will be in such joint and muscle pain it will refuse to move; it is not uncommon for an owner to have to carry a sick dog into the animal hospital.  Over the span of two or three days a dog can progress from normal to completely unable to walk due to generalized joint pain.  In addition to joint damage, the bacteria can affect the dog's heart muscle and nerve tissue.  If the disease is diagnosed in time, treatment can cure the dog before permanent joint or nerve damage occurs.  Certain antibiotics, such as the Tetracyclines, are very helpful in eliminating the disease.
   
Generally, the diagnosis of Lyme Disease is based upon clinical signs and history.  For example, if a dog ran or played normally a few days ago, has had no signs of trauma or previous arthritic discomfort, and now displays tenderness upon palpation of the affected limb and has a mild fever and swollen lymph nodes, I'm going to seriously consider Lyme Disease as a possible diagnosis.
   
On the other hand, just as in human medicine, Lyme Disease is called "The Great Imitator" because it has often been mistakenly diagnosed when another disorder is present, such as an autoimmune disease, lymph tissue cancer, Blastomycosis, or septicemia.  Just as vexing is the fact that at times other similar-appearing diseases are diagnosed when the culprit is actually Lyme Disease.  There are published reports of Lyme Disease being misdiagnosed and over diagnosed in human medicine.

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Keeping other disorders in mind, if I suspect Lyme Disease, I start treatment immediately, generally prescribing an antibiotic such as tetracycline and possibly some aspirin if the dog is in a lot of pain.  Many veterinarians do not wait for blood tests to confirm the tentative diagnosis because in dogs the information obtained may be confusing and require too much time to hear lymevaccine back from the lab.  I have seen patients that from clinical experience I know have Lyme Disease, yet their blood test curiously indicates no exposure to the disease.   And there are numerous cases of normal-appearing, healthy dogs with positive blood tests for Lyme Disease.

Fortunately, over ninety percent of dogs treated within the first week of obvious signs of Lyme Disease will respond rapidly to treatment with a tetracycline antibiotic.  This medicine is administered for at least three weeks.  In my experience, five percent of dogs will have some type of relapse of signs such as cardiac or neurological difficulties even after treatment .  Some of these patients will experience chronic, lifelong joint pain from the damage caused by the bacteria and its direct and indirect stress to joint tissues.  The earlier the antibiotic is started in the course of the disease, the better the patient's chances of a complete recovery.

Can a dog contract Lyme Disease a second time?  Yes.  But, quite honestly, we don't know for sure if the reoccurrence is a second, distinct infection or a flare-up of the original episode (because the Borrelia organism replicates quite slowly).  And, since dogs can harbor the bacteria in their tissues a long time before the disease is evident, Lyme Disease cases are showing up all year long.  In the northern states, however, the summer months are the busiest for Lyme Disease case presentations.

Lyme Disease in Humans
    In humans Lyme Disease is defined as a "multi-system tick-borne disorder caused by the spirochete bacteria Borrelia burgdorferi."  Since 1982, when the causative organism was positively identified, numbers of cases in humans have made Lyme Disease the number one tick-borne disease in the U. S.   Widely present in Europe and Asia, with occasional reports from Africa and Australia, Lyme Disease is somewhat localized in the U. S. with 90 percent of human cases reported from the Northeast, North central and Pacific Coast states.  But the geographical distribution is an ever-changing dynamic.
   
Nearly 10,000 human cases of Lyme Disease were reported to the Centers for Disease Control in 1992, compared to only alymebullseye1small few hundred in 1982. And in 1998 almost 17,000 cases were reported.  Actually, since 1982 over 120,000 cases have been reported in humans.  Eighty percent of these human cases resulted from the bites of the nymph-stage ticks from May through August.  So it is the intermediate, poppy-seed sized form of the tick most likely to transmit the disease to humans.  In the United States, the human disease is primarily localized to states in the northeastern, mid-Atlantic, and upper north-central regions, and to several areas in northwestern California.
    In previous years physicians have had a difficult time positively identifying Lyme Disease in humans.  "The Great Imitator" likes to be confused with other disorders, and in the past, blood tests for Lyme Disease often gave obscure answers.  Luckily, that changed in January of 1994, when the Mayo Clinic in Rochester, Minnesota, announced the availability of the Polymeraselymebullseye2small Chain Reaction (PCR) test.  With this new method, utilizing spinal or joint fluid, physicians can now say with greater certainty whether or not a patient has Lyme Disease.   This is a great help to physicians since Lyme Disease in humans has become quite "popular" lately.  It is not uncommon for someone to hobble into the physician's office and even before being examined announce, "I've got Lyme Disease."  The PCR test will help to establish the truth of such pronouncements.
   
Physicians describe different stages of the disease in humans with variable signs being displayed, including fatigue, fever, headache, muscle/joint pain and enlarged lymph nodes.   Swollen knees are a common symptom.  As many as 50 percent of patients in the U. S. show a curious skin rash called a "Bullseye" rash or erythema migrans, which emanates from the tick bite area.  (Erythema migrans is not common in dogs and I have seen only two cases displaying the red rash.)
   
In humans Lyme Disease is usually treated with antibiotic of the tetracycline type.  If cardiac or neurologic signs are present, other medications may be employed, including amoxicillin, ceftriaxone (administered intravenously), and doxicycline.

Vaccinations for Lyme Disease in humans have been available but are not in widespread use at this time (2004) and may even be difficult to acquire.  Generally, only those individuals at high risk of contracting the disease (game wardens, forestry workers, etc.) will seek vaccination for Lyme disease.
(Tick and human rash photos are courtesy of LymeNet.org)
 
Prevention of Lyme Disease in Dogs
lymevac1 There are  three Lyme vaccines approved for use in dogs.  Keep in mind, though, that no vaccine for humans or canines will be  100% effective and protective against the disease.  As with any vaccine there are a number of variables that can impact each individual's response to a vaccine.  Think of vaccination for Lyme Disease as one tool you can use to decrease your dog's chances of contracting the disease.  For helpful information on the advisability of vaccinating your dog, contact a vaccine manufacturer or discuss this disease with your veterinarian.

    The first and most obvious technique to assist in prevention is to keep the tick population  to a minimum.  There are safe and effective insecticides that can be used in the dog's usual environment  (e. g., a 50-foot radius around the dog house).  In addition, there are new chemical agents that you apply once a month to small areas of the dog's skin; thereafter, the agent spreads over the dog's body via the oil on its skin and kills ticks before they get a chance to inject the bacteria into the dog via the tick's saliva.  One of the most commonly used anti-tick medications is called Frontline Plus and is available in a liquid spot on application or as a spray.  When it is applied to the dog or cat it spreads through the skin's oil layer. K9Advantix is another prescription anti-tick medication that repels mosquitoes and kills fleas.  Sprays, shampoos, collars, powders and dips are often used too (in these products the chemical ingredient permethrin is more effective than pyrethrin).  Sprays, collars and dips repel and kill ticks to some degree, with some collars being the least effective, although many people feel that the tick collars containing the product Amitraz works quite well.
   
Please note:  Most of these agents will kill the tick after it climbs aboard the dog.  The longer the tick is attached and biting, the greater the risk of bacterial transmission... IF the tick carries the Borrelia bacteria in the first place.  Remember, no repellent will keep every single tick off a dog.  
   
Hunting dog owners in northern Wisconsin have found that spraying their dogs with a topical spray just prior to an outing in the woods decreases the numbers of ticks picked up by their dogs.  Caution!  Do not "double up" on insecticides or repellants.  If your veterinarian has prescribed a topical once-a-month flea and tick product, always consult your veterinarian before applying any additional insecticide/repellent product!  By the way, insect repellents designed to be applied to clothing should not be used in dogs.  If you own a kennel, check with your veterinarian about tick control procedures tailored for your kennel setup.  Check with the Environmental Protection Agency (www.epa.gov) for more information about pesticides.
   
lyme4 Examine your dog after outdoor excursions and carefully pick off the ticks you find.   But remember how tiny the Ixodes larvae and nymphs are; they'll be a challenge to remove without crushing them. With tiny tweezers, gently grasp the tick as close to the dog's skin (or your own!) as possible and gently pull away from the skin.  Ticks do not burrow under or into the skin but rather attach to the skin surface with two claw-like mouth parts.  Try not to crush the tick.  After removal, cleanse the area with antiseptic.
   
Humans should wear clothing that covers as much skin as possible to prevent the ticks from contacting the skin.  And the use of light-colored clothing will make observation of the dark-colored tick easier.  Other hints:  Avoid fields and grassy areas; apply repellents according to directions; and examine yourself closely for ticks after a day in the field. We live in a diverse, intricate  and ever-changing natural world.  It is full of challenges, always prompting us to better understand diseases and vectors, predator and prey, life cycles and evolution.  The bacteria that causes Lyme Disease has found a niche in this natural world and will share the planet with us for a long time.  The challenge is to learn all we can about it!
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Update! (March, 2005)
lyme5 Veterinary science is advancing in its ability to detect immune system indicators of exposure to Lyme Disease in dogs.  Blood tests can now differentiate between immunity derived from natural exposure and immunity derived from a previous vaccination.  Doxycycline, tetracycline and amoxicillin continue to be effective choices as an antibiotic but treatment must continue for a few weeks after all signs of the disease are absent from the dog.  Vaccines to prevent the disease are becoming more effective and longer lasting.  Any disease has the potential to mutate or adapt to new conditions so keeping ticks off of the dog, vaccinations (consult with your veterinarian... take a look at the "vaccine issue"), and awareness of the signs of Lyme Disease in you dog will all be helpful in preventing this infection from disabling your canine companion.

Researchers at the University of North Carolina and the Centers for Disease Control and Prevention have found that during feeding, the tick vector for Lyme Disease actually transmits a highly variable population of Borrelia burgdorferi (the causative agent) into the host. In contrast, when the tick isn't feeding, the population is fairly homogenous. What this means is that the bacteria essentially adapts during the transmission process to maximize the chance of infecting the host.  Intriguingly, the fact that the tick spits so many different "flavors" of B. burgdorferi into the host seems to explain an observation made several years ago: Lyme bacteria delivered by ticks evade the host's immune response more successfully than do cultured bacteria injected into animals. The team suggests that future efforts to develop better vaccines could either focus on antigens produced within the tick before the bacteria population diversifies, or on surface proteins common to all of the otherwise variable bacteria. (AnimalNet - Scientific American Daily)

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Lyme Disease Fight Goes to No.10

An E-petition has been put on the 10 Downing Street website to increase awareness and funding towards diagnosis and treatment of Lyme Disease.

The petition asks that "funding and resources be urgently made available and used to improve all aspects of the diagnoses, treatment, prevention, monitoring, public awareness and research of lyme disease and its associated tick borne infections, in order to improve the poor clinical outcome with these diseases in the UK.

You can sign the petition at http://petitions.pm.gov.uk/Lyme-Disease/

At the time of writing, there were more than 1,500 signatures, and there's still plenty of time to add your vote - the deadline is 28 February 2008.

The threat of Lyme Disease was highlighted when US President Bush was successfully treated last August for "early localised Lyme Disease".

He developed the characteristic 'bulls-eye' rash after mountain bikeing.

For more on the disease visit the website www.lymediseaseaction.org.uk

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Ticks on Dogs
 About Ticks


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The above information is simply informational. It's intent is not to replace the advice of a veterinarian nor to assist you in making a diagnosis of your pet. Please consult with your own veterinarian for confirmation of any diagnosis. Your pets life may depend on it.