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My Dog Tested Positive for Lyme Disease: Now What?

This spring, dog owners may have noticed that we are using a different heartworm test this year. The test is called a 4DX and it detects antibodies to heartworm plus the tick borne diseases Lyme, Erlichia, and Anaplasma.

It can be scary and confusing to get positive results, so I’d like to take a few posts to go over what positive results on theses tests mean and what we recommend doing about them. This post will focus on Lyme.

First: Don’t panic! A positive Lyme test does not necessarily mean your dog has an active Lyme infection right now requiring treatment. It means that at some point your dog has been exposed to the Lyme organism and produced antibodies. The test does not tell us if the exposure was recent or in the past or whether your dog requires treatment.

How do we tell the difference? Primarily by whether your dog is currently showing symptoms of Lyme disease or not and some additional testing. Only about 5% of dogs exposed to Lyme disease will become sick; the rest successfully fight the bacteria off and show no or very mild symptoms. Symptoms of Lyme disease may wax and wane and include lethargy, high fever, loss of appetite, lameness (which may shift from leg to leg or affect all legs with a “walking on eggshells” appearance), and enlarged lymph nodes.

If most dogs don’t get sick from exposure to Lyme and a positive test doesn’t necessarily mean a dog needs treatment, why do we do it or care about a positive test? There are a few reasons:

  1. There are some rare but very serious complications that can be associated with Lyme disease; these include Lyme nephritis, a type of kidney disease. Even a dog who showed only mild symptoms may develop these complications. Knowing that a dog has had exposure gives us an opportunity to identify dogs with nephritis and intervene to prevent progression.
  2. Evidence of exposure to Lyme tells us whether preventative measures such as tick control products have been effective and guide future decisions about vaccination for Lyme (as natural exposure does not give any lasting immunity to future infections for this disease).
  3. Your dog’s exposure to Lyme disease reminds you that you need to be careful, too! Since most of us are spending time in the same places our dogs are, they can be an important sentinel for our own risks of exposure to tick-borne diseases.

Soooo… after all of that, what do we actually DO if a dog tests positive?

For a dog with a positive test but no current symptoms of Lyme disease, we recommend a test called a urine protein:creatinine ratio or UP:C. This test screens for abnormal protein loss in the urine which is an indication of Lyme nephritis. If that test is normal, no further testing should be needed. However, if you are not using a flea/tick control product, consider starting one and consider vaccinating your dog for Lyme.

For a dog with symptoms of Lyme disease and a positive test, we treat with an antibiotic called doxycycline for 30 days plus pain relievers as needed. Typically we see an improvement in symptoms within 1-3 days once starting treatment. We also recommend the UP:C test described above as well as chemistries to check kidney function and blood pressure. For a dog with Lyme nephritis, additional treatments may be needed.

I hope this post has demystified a positive Lyme test and explained why we have added them to your dog’s yearly heartworm test. We want you to enjoy the great outdoors with your dog but keep them safe, too! As always, if you have additional questions please feel free to speak to one of our doctors.

Karen Christopherson DVM CVA