The Sonoma County Gazette: Community News Magazine
Sonoma County Gazette
| more

Photo Gallery

Family Pet Animal Care - tick-borne disease


Family Pet Animal Care - November 2015 

by Dr. Michael Trapani

Everyone seems to have different ideas about tick-borne disease. It’s the story of the blind men describing the elephant: Everyone has a different perception that is determined by their point of view, and everyone believes that their perception is the correct one. Obviously, this cannot be true. Here, then, is one veterinarian’s perception, which is, of course, the absolutely complete and correct view. (Queue laugh-track.)

Lyme disease is the poster child for tick-borne illness. Lyme was first recognized in the early 1970s, when a mysterious group of rheumatoid arthritis cases occurred among children in the town of Lyme, Connecticut. By the early 1980s, Dr. Willy Burgdorfer, established the connection between deer ticks and Lyme disease, and proved that a corkscrew-shaped bacterium (a spirochete, similar to the leptospirosis agent we discussed last month) caused the disease. His accomplishment was forever commemorated when the disease agent, Borrelia burgdorferi, was named in his honor. Lucky guy.

The Lyme agent is injected into the victim’s body when certain families of tick, most commonly the black-legged tick (Ixodes pacificus) in our area. In data published by the Sonoma County Public Health Laboratory, between 2009 and 2014 roughly 2% of these ticks were found to contain Lyme bacteria. Black-legged ticks are smaller ticks with small (roughly 1/8 to 1/4 inch) orange bodies and black legs. Other local ticks, such as those belonging go the Dermacentor family, are not thought to transmit Lyme disease, although they may transmit other pathogens. Here is a graphic showing Ixodes scapularis, a species similar to local Ixodes ticks.

In humans, Lyme disease affects many body systems to produce a huge range of problems. Not all patients with Lyme disease have all symptoms, and many of the symptoms can occur with other diseases, making Lyme particularly difficult to identify. The incubation period from tick bite to the start of symptoms is usually one to two weeks, but can be shorter, or much, much longer.

The classic sign of local infection with Lyme disease is a circular, outwardly expanding rash, which occurs at the site of the tick bite three days to one month after the bite. The rash is red and may be warm, but is generally painless. Typically, the inner and outermost portions remain red and the area between fades, giving the rash a bull’s eye appearance. This rash is found in less than half of all human patients and almost never in animals, so lack of a rash does not rule out Lyme infection. Other signs, such as flu-like symptoms, headache, muscle soreness, fever, and malaise may occur with or without the rash. 

Days to weeks after the onset of local infection, the Borrelia bacteria may begin to spread through the bloodstream. Rash may develop at sites far from the original tick bite. Other symptoms include migrating pain in muscles, joints and tendons, and dizziness.

An unknown but possibly large fraction of victims go on to develop nervous system problems such as facial palsy, and/or meningitis causing severe headaches, neck stiffness, and sensitivity to light. Inflammation of spinal cord nerve roots can cause shooting pains that may interfere with sleep and cause abnormal skin sensations. Inflammation of the brain may occur, leading to memory loss, sleep disturbances, mood changes, or even grand mal seizures. Some people have described altered mental status as their only symptom.

Ultimately, Lyme disease victims can develop chronic, severe symptoms in many parts of the body, such as the brain, nerves, eyes, joints, and heart. These impairments can be both permanent and disabling. Possibilities include polyneuropathy with shooting pains, numbness, and tingling in the hands or feet. Lyme encephalopathy may occur causing subtle to severe cognitive difficulties, insomnia, a general sense of feeling unwell, and changes in personality, mental impairment, brain fog, migraines, balance issues, leg weakness, bladder problems, vertigo, and back pain.

Lyme disease is generally thought of as a disease causing arthritis, which usually involves the knees, but arthritis represents fairly small part of Lyme pathology. In a relatively small number of people the arthritis occurs in other joints, including the ankles, elbows, wrists, hips, and shoulders. Pain is often mild to moderate, though it can be quite severe, sometimes with swelling of the involved joint.

Recently, the Centers for Disease Control and Prevention revised their estimate of US Lyme disease infections from 20,000 to 30,000 cases per year to a whopping 335,000 cases per year. This ten-fold increase in the number of expected cases has immense implications on the human risk of Lyme disease here in our area. Sonoma County reported only 78 human Lyme cases between 2005 and 2014. The CDC’s new estimate suggests that ten times as many people, or more, have gone undiagnosed.

But enough of this human stuff. In veterinary medicine, we consider Lyme disease to be a COMMON problem, common enough for many veterinarians (myself included) to recommend yearly screening for Lyme and other tick-borne diseases along with the standard yearly heart-worm test. Here in Bodega Bay, seldom does a month goes by in which we fail to find dogs whose Lyme screening tests are positive. Other tick-borne diseases, such as anaplasmosis and ehrlichiosis represent an additional subset of tick-borne infections which are regularly diagnosed through routine blood screening tests. 

It gets worse: This class of illness, termed “vector-borne” diseases, represents a growing class of disease agents with new members being discovered on a regular basis. For example, a recent publication described Borrelia miyamotoi disease in humans, another tick-borne disease agent that appears to be even more severe than Lyme itself. New forms of Anaplasma and Ehrlichia are discovered periodically, with implications for the health and safety of dogs and people. But how long will it take before technology catches up and fast, inexpensive screening tests are available to diagnose these new tick-borne agents as we currently diagnose their cousins? Humans have the potential to become infected with all of these agents, so if our dogs are commonly infected, I have every reason to believe that humans are also being exposed.

I am reminded of the situation some years ago, when rapid Lyme screening tests first became available in veterinary medicine. Suddenly, there seemed to be an epidemic of Lyme disease in dogs. In fact, what we experienced was an epidemic of Lyme TESTS. It is amazing what we do not see when we do not look. The same has been true when Anaplasma and Ehrlichia tests were added to the annual heart-worm / Lyme screening test. Suddenly, diseases that we had never recognized became commonplace.

One pitfall of testing is the mistaken belief that a negative test for Lyme (or any other tick-borne disease) constitutes proof that the disease is not present. The methodology of our screening tests requires that the patient produce specific antibody to the disease agent in order to trigger a positive result. If the disease has not been present long enough to trigger antibody production, or the patient has individual reasons for not producing that antibody, or if the disease agent is a related but undiscovered cousin to the disease agent detected by the test… or if any of a hundred other possible factors interfere with test effectiveness, then a negative test result can occur in the presence of active disease. The least reliable negative test is the test that is not done, as is too often the case with Lyme, which is sometimes considered a disease that’s “too rare to bother testing for.”

Where tick-borne diseases are concerned, dogs serve as a sentinel species for human health. People are exposed to the same organisms and vectors as their dogs, so when those dogs are commonly infected with things like Lyme or ehrlichiosis, it’s a good bet that the humans in that immediate area are affected as well.

My tick-borne disease patients fall into three categories: The first group are the dogs who seem perfectly normal but show positive antibody levels to routine annual testing. The second group is usually older dogs with obscure malaise and weakness. Their owner often thinks that they’re “just getting old” and “slowing down,” then we test them and a fraction will come up positive for Lyme. The third group is the “holy cow” patients who show up with anything from severe bone marrow suppression from Ehrlichia to severe seizures and meningitis from Anaplasma, to “you name it.” It seems that many poorly defined problems in dogs can be caused by tick-borne disease. Sorting through these things can be a real challenge. You can’t just look it up on Google and think you understand tick-borne disease!

What to do? See to it that your dogs receive their annual check-up and heart-worm / tick-borne disease test, which requires only three drops of blood to perform. These test results are available in 8 minutes! Be suspicious of any changes in activity or appetite in your dogs and seek veterinary advice. Use reliable flea and tick control measures year round, and ask your veterinarian about the new, super-effective products that have recently become available. Consider vaccinating puppies for Lyme disease and keep the vaccinations up to date. When you find a tick on your dog (or yourself) preserve the beast in a plastic bag and contact your veterinarian (or physician) to find out how you can have the tick identified. 

Most of all, be aware that our area is populated with ticks capable of spreading a number of serious diseases, including Lyme, and that these diseases are either rare or common, or both, depending upon with whom you’re speaking. Where your own health is concerned, be your own advocate. When in doubt, seek a second opinion.