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TICK-BORNE DISEASE cont’d from page 32
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”
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.
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.” Many poorly defined problems in dogs can be caused by tick-borne disease. Sorting through these things can be a challenge. You can’t 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.
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