Lyme disease vs. “Blue Dot” disease

I had two patients seen by another office recently for possible Lyme disease.  One was a little terrier dog who was feeling well, but her owner discovered an attached tick on her undercarriage, removed it, and noticed a ring of reddened skin around the attachment site.  Because the owner was concerned about the “bullseye” lesion of Lyme disease, off she and the terrier went to Hospital Big (it was a Saturday, my office is closed).  Lyme (and heartworm, Erhlichia, Anaplasma) test, doxycycline (antibiotic), and some other stuff (owner did not share an invoice with me):  $500.  Terrier (with no symptoms of Lyme disease) did well on a course of antibiotics.

Doggie number 2 (a fancy Italian breed)  was presented to Hospital Big, again on a Saturday, for extreme lameness, poor appetite, fever, and a mild ear infection.  Giardia test, exam, ear cleaning, ear potion, Lyme (etc.) test, NSAID, doxycycline, anti-nausea injection:  $555.67.  Fancy dog responded very well to treatment and made a full recovery.

Some highly opinionated thoughts on these two cases.  In the first case, the terrier simply had an attached tick–something that is dead common this time of year in Bucks County.  Even pets that are using great tick products (and there are now many great tick products), ticks may still attach before they become ex-ticks.  Ticks bites can result in a non-specific red circular rash, but dogs do not develop the erythema chronica migrans that humans do with exposure to the Lyme organism (Borrelia burgdorferi).  So when a client brings a dog to my office with an attached tick and accompanying rash, I will tell the owner that this is a perfectly normal and perfectly innocent lesion, and that absolutely no treatment of any sort is required.  Someone ought to have told the owner that, IMO.  Instead, hundreds of dollars was spent on a nothingburger of misplaced worry on the part of the dog’s very caring owner.  Dogs are, BTW, extremely resistant to symptomatic Lyme disease–only a small fraction of infected dogs will develop any problem related to their infection, in contrast to humans, who are highly vulnerable to symptomatic Lyme disease (although many only develop the pathonognomic erythema chronica migrans rash).  Incidentally, cats, deer, sheep–lots of species are completely immune to Lyme disease despite ease of becoming infected with the causative organism).  My office has stopped using the 4-way diagnostic Heartworm/Lyme/Ehrlichia/Anaplasma test for routine HW screening because of the very common Lyme positive results in perfectly normal dogs.  And treating “blue dot” positive “Lyme disease” is not safer in any way than not treating.  There is absolutely no evidence that feeding antibiotics to dogs with blue dots and no symptoms does anything helpful (other than to pharmacy revenues).

The second dog, our Italian friend, is quite a different story.  He was very sick (his owner told me she thought he was dying) and had several of the classic symptoms of canine Lyme disease.  Fever, dramatic lameness (we sometimes call them fracture lame–as bad as a broken bone), poor appetite.  For this patient, Lyme testing is clearly indicated, and quite reasonably antibiotics, too.  Pain relief–definitely.  Some of these dogs are in need of NSAID and tramadol (an opiate analog).  For this patient, full credit for the medical approach and a very happy outcome for the dog (and owners).

Screening for infectious diseases sometimes produces results that are worrying but not relevant to the patient and its symptoms.  There is considerable science/epidemiology around the use of tests for screening vs. sick patient diagnosis.  In general, tests perform better (they are more accurate) when disease-appropriate symptoms or risk factors are present, and perform considerably more poorly when they are absent.  This is a fact of almost all tests, though it sometimes frustrates dog owners who insist that their dog was “diagnosed with Lyme disease” (or something else) absent a single symptom of said disease.  I would call that “Blue Dot” disease, an incurable though expensive condition brought on by inappropriate testing.

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