Lyme Disease In Dogs And Their Owners
By Ron Hines DVM PhD
Lyme disease is caused by a bacteria, Borrelia burgdorferi. This particular group of bacteria are called spirochetes. Under the microscope they have a distinctive spring-like shape. This organism is transmitted through the bite of an infected tick. It was first identified in humans in 1975 and in dogs in 1984. Lyme disease is a perplexing condition because it can affect so many organs of the body. This allows it to produce a wide variety of symptoms that mimic many other diseases. Because if this, it is sometimes called the great pretender. It is also a very common false diagnosis. We still have a great deal to learn about the transmission, effects, and treatment of this disease. Lyme disease first made its appearance near the Connecticut town of Lyme. The disease has been reported in every part of the United States but it is more common in certain areas than others. In this Country, more than 90% of lyme cases occur in the Northeast and Northcentral states. Northwestern California and Mississippi also have a large number of cases. It is fairly common in dogs, and occasionally seen in cats. Cases of the disease in dogs and people are on the rise because of increases in the number of deer and urban wildlife on which the tick feeds and incursion of housing developments into woodland areas.
The Tick:
Remember that the tick is simply a method by which the bacteria gets around. It does not play a part in the disease. The most likely time to be bitten by an infected tick in the USA is April through November. At least three species of tick are known to transmit Lyme Disease. However, the great majority of transmissions are due to the bite of an extremely small (poppy seed sized) tick called the deer tick or black-legged tick. Although it is called the deer tick, it feeds on many animals including birds, raccoons, skunks, opossums dogs and cats. Its scientific name is Ixodes scapularis and it is so small that it can be easily overlooked. The infected tick must remain attached to the dog or human for a day or two before it can transmit the disease. The tick obtains its infection by feeding on a white-footed mouse (Paramyscus) which is itself infected with the disease. This tick is now being spread rapidly on infected migratory birds and coming into our home environment more as we build our homes in an urban sprawl that penetrates the countryside.
Symptoms And Diagnosis:
The most common symptom of Lyme disease in dogs is a reoccurring lameness that may shifts from leg to leg. Most commonly, it is a front leg that is effected and the lymph node on the shoulder of that leg may be enlarged. Many of the sick dogs are depressed and run fevers. Occasionally I find that the superficial lymph nodes all over the dog’s body are enlarge. It is common for infected dogs to have hot, painful joints when lameness is present. They may yelp when these joints are pressed and be quite reluctant to walk. When they do walk, they walk with a stiff shuffling gait and an arched back because of the pain. Unfortunately exercise-induced sprains, arthritis, hip dysplasia and lumbar or cervical spinal problems present very similar signs. When I am fortunate, I will notice ticks present on the dog. A classical red circular band often surrounds the tick or the place where the tick was attached. This mark is called a target or bullseye lesion. The redness follows the routs of the bacteria migrating through the skin from the site of the tick bite.
When the disease is missed or miss-diagnosed, the bacteria can spread to the heart (myocarditis) the kidneys (glomerulonephritis) or, more rarely, the nervous system. Many cases of Lyme disease are asymptomatic or subclinical. That is, the dog appears healthy.
When we suspect a sick dog might have Lyme disease we run diagnostic test on its blood. There are two tests available, the ELISA and the Western Blot test. Of the two, the Western Blot test is the more sensitive. When a dog has been vaccinated for Lyme disease but still shows symptoms we must run a special test because of the residual effects of the vaccine. These tests are not infallible and symptomatic dogs that return negative test results may still become symptom-free when given the special antibiotics used to treat the disease. Dogs that do not improve after antibiotic therapy probably were not suffering from Lyme disease even if the laboratory tests were positive. Numerous cases of normal-appearing, healthy dogs with positive blood tests for Lyme Disease exist.
When dogs are not treated, they progres ls from the early to the late stage of the disease. In these later stages the nervous system or heart may be damaged by the bacteria but joint pain and skin rash subside.
People who have contracted Lyme borreliosis from an infected tick also show an unusually wide variety of symptoms. When I contracted this disease with high fever in the Middle East some forty years ago it was misdiagnosed as colera. It was only when the joints of my hands became swollen and painful that Lyme disease was suspected. The best test for the disease in humans is the polymerase chain reaction test. Early in the disease the organism spreads through the bloodstream and lymph system. During this stage, lymph nodes may be swollen and painful. One early symptom is erythema migrans, the target lesions, as well as larger areas of rash. These skin rashes often clear in the center forming a classic "bulls-eye” pattern. Others develop muscle and joint pain called myalgia and arthralgia. Sometimes, a flu-like illness and swelling of the lymph nodes of the throat occurs. When it does, it differs from the flu in that there is no stuffy nose, coughing or sore throat. If these symptoms are severe or accompanied by marked arthralgia (joint pain), myalgia (muscle pains), headache or neck stiffness, it is likely that there has been some secondary spreading of the infection to these parts of the body. In still other people, the first sign of the disease is nerve damage or radiculopathy that can occur months to years after infection. In some cases, only the knee(s) becomes swollen and painful, while in other rare cases the heart is attacked (myocarditis, heart block arrhythmias). Inflammation of the testes and eye have also been reported with Lyme disease.
Late in Lyme disease in humans arthritis may occur. Other late-occurring symptoms include nerve damage or heart damage without initial inflammatory signs and an autoimmune, lupus-like, disease. These wide variety of signs are even more perplexing because laboratory tests performed on people are no more accurate than those performed on dogs.
Borrelial lymphocytoma is a rare form of Lyme disease in people in which an earlobe, nipple or scrotum develops an intense bluish-red patch of skin.
Acrodermatitis chronica atrophicans is a lyme-related skin lesion with a shiny, papery feel that begins as a bluish discoloration. They form most commonly on the lower legs of elderly people. This form of the disease is most common in Europe.
When Lyme disease attacks the nervous system of humans, paralysis, memory loss and depression can occur. Some times it manifests itself as chronic fatigue syndrome.
Lyme arthritis in people is common in the United States but rarer in Europe. It usually affects the large joints of the limbs. The most commonly affected joint is the knee.
Treatment:
Doxycycline and ammoxicillin will cure Lyme disease if administered early to dogs and given long enough. Treatment should last a minimum of a month. Aspirin or one of the newer non-steroidal anti-inflammatory drugs can be used to control the pain. Humans are treated with the same drugs. If the organism has caused cardiac or neurological disease, ceftriaxone may be administered intravenously. Some patients develop life-long joint pain due to damage already inflicted. Other damage can also be non-reversible.
Outcome Or Prognosis:
When the diagnosis is correct dogs should begin improving within two weeks of starting antibiotic therapy. Relapses are common when the antibiotic is stopped too soon.
Prevention:
Check your pet and yourself daily for ticks and remove them. For you or your pet to contract Lyme disease the tick must stay attached one or two days. Be particularly thorough in brushing and combing if your pet has been in high weeds or brush. In removing the ticks try not to crush them. The best way I have found to remove them is to grasp the ticks mouth parts as close to the skin as possible with a pair of small tweezers and pull the tick away removing all of the head a small tag of skin. Ticks secrete a liquefying enzyme into the skin surrounding their mouth parts. Removing a small tag of skin with the tick allows for quicker healing in the long run.
Treat your yard with insecticides approved for controlling ticks or hire a professional to do so.
Uses shampoos and dip products that kill and repel ticks.
Keep your yard closely mowed. Clear brushy areas that harbor ticks and trim your trees so that sunshine reaches the ground.
For dogs, collars that contain amitraz (Preventic Collars) combined with monthly fipronil spray (Frontline Plus) are quite effective in repelling ticks. Frontline spray is more effective than the dropper form. Preventic collars must not be used on cats. However, Frontline spry works well on cats.
Vaccination:
High-risk dogs are those that roam around in meadows and woods infested with ticks. Only these dogs should be vaccinated for Lyme disease. Following an initial series of two injections given 2-3 weeks apart your pet should be given a yearly booster. There is a lot of controversy surrounding yearly vaccination for Lyme and other canine diseases http://www.2ndchance.info/dogvacs.htm . It is true that in the past we over vaccinated all pets. However, lyme is a very serious disease and if you can not keep ticks off of your pet with collars and sprays then the vaccine is worth whatever small risk that may be inherent in its use.
A vaccine for Lyme disease in humans (LYMErix™ SmithKline Beecham Biologicals, Reixensart, Belgium) was available but it was not widely used because of potential side effects. The CDC recommended its use in people with very high exposure to Ixodes ticks http://www.cdc.gov/ncidod/dvbid/lyme/vaccine.htm It is currently off the market.
