Is Lyme Disease Over-Diagnosed and/or Over-Treated in Dogs?
by Lorie Huston, DVM on July 10, 2013
Lyme disease strikes fear into the hearts of many dog owners. I understand that. And I’m not insinuating that Lyme disease is not a threat or that dog owners should not worry about it. However, I also think that dog owners should be aware of the facts surrounding the disease and understand the basis of testing and treatment for Lyme disease.
Lyme disease in dogs is a very different disease than that seen in people. Many veterinarians recommend routine screening for Lyme disease using a patient-side test known as the SNAP 4DX, which tests for the presence of a specific antibody (known as C6) present in dogs exposed to the organism that causes Lyme disease, Borrelia burgdorferi. In endemic areas, as many as 50-70% of dogs tested can test positive. However, a positive test does not equate to illness. In fact, as many as 90-95% of dogs testing positive for Lyme disease never show signs of disease.
In 2003, the American College of Veterinary Internal Medicine (ACVIM) issued a consensus statement relating to Lyme disease in dogs. This consensus statement is founded on “evidence-based medicine, but if such evidence is conflicting or lacking, the panel provides interpretive recommendations on the basis of their collective expertise.” The five-member panel that put together this consensus statement was selected by the Board of Regents with input from the general membership of the ACVIM. As such, it is an authoritative and carefully considered document containing the opinions of five of the top experts in the field and the statement explores many aspects of Lyme disease in dogs.
In regards to routine screening for Lyme disease in healthy dogs, the panel concluded “Whether healthy dogs should be screened for antibodies against Bb (Borrelia burgdorferi) proved controversial, and a consensus could not be reached.” The statement provides a list of reasons commonly given for advocating the screening of healthy dogs as well as an opposing list of reasons for not screening these dogs.
The list of reasons to consider screening healthy dogs includes the following (this is quoted directly from the consensus statement):
- We might detect a potentially dangerous disease (Lyme-associated nephropathy) before clinical illness develops by screening and monitoring seropositive dogs for proteinuria. Although checking for proteinuria is part of an annual wellness examination, if a dog is known to be seropositive, one might want to check for proteinuria more frequently than annually, especially in retrievers and Shelties.
- We can track seroprevalence data in the practice area in both healthy and sick dogs.
- Our vaccination protocol can be individualized because there is no evidence that vaccine is helpful for seropositive dogs.
- We can provide information about the environment because dogs are sentinels.
- We can inform owners about landscaping changes and the importance of checking daily for ticks on themselves as well as their pets, and we can emphasize the importance of using tick control.
- We can inform owners that if they remove an engorged Ixodes tick from a person, they should call a physician who could prescribe 1 dose of doxycycline (200 mg) to be taken within 72 hours, which has been shown to prevent Lyme disease in people. Owners are very thankful for this public health information. No such study has been done on dogs.
Arguments against screening healthy dogs (or treating them) include the following (again quoted directly from the consensus statement with bolding added to some of the most important points by me):
- Routine testing often results in overdiagnosis and overtreatment of dogs on the basis of a test that does not diagnose Lyme disease nor predict whether Lyme disease will ever occur; most seropositive dogs will never become ill with Lyme disease and do not need to be treated.
- Overtreatment with incomplete clearance of the organisms potentially can induce resistant strains.
- Overuse of antibiotics generally increases other microbial resistance in the environment.
- Not all dogs are cleared of infection even after 1 month of antibiotics. (Editor’s note: Evidence suggests that very few dogs are actually completely cleared of infection.)
- Immunity is not permanent, and treated dogs could be reinfected.
- Subclinically infected seropositive dogs might be in a premunitive state that could be protective.
- Drugs used for treatment of Lyme disease have potential adverse effects.
- Detection of positive test results could cause unnecessary owner distress.
- False positive test results involve expense for the owner, unnecessary owner distress, and potential induction of drug reactions in animals that do not need to be treated.
- Lyme endemic areas are already well-known, and tick control and public health information should be recommended in all Lyme endemic areas regardless of results of blood tests.
- Screening for proteinuria should be part of a routine wellness examination and not done merely because of a seropositive test result.
Testing a dog that is potentially suffering from Lyme disease is, of course, a no-brainer. These dogs absolutely should be tested. However, screening dogs that are healthy is far from being a black and white decision.
Treatment is the same. Again, treating a positive dog that is sick with symptoms consistent with Lyme disease is a no-brainer. Obviously, these dogs need to be treated. However, the necessity of treating a healthy dog with a positive screening test is more ambiguous. The consensus statement advises against the treatment of these dogs for the reasons listed above.
Is there a right or wrong answer here? No, there’s not. My personal feeling is that screening a healthy dog does not provide any additional useful information to me as a clinician so I don’t recommend it. I also don’t recommend treating healthy dogs that have tested positive on a screening test for Lyme disease. In my opinion, treatment is not without risk and a positive benefit to prophylactic treatment has not been demonstrated. In other words, we simply haven’t been able to show that treatment actually prevents disease from occurring in these dogs. Therefore, I prefer to see my clients spend their hard-earned money on flea and tick preventive medication and other preventive health care for their dog although I will not deny antibiotics to a healthy but positive dog if the owner prefers to use them.
I do not condemn other veterinarians (or dog owners) who feel differently. I realize that there are many different viewpoints on this issue and there is much we don’t know at this point. Rest assured that I continue to closely monitor developments in this arena. Research continues and may eventually provide more definitive answers, at which time I will reevaluate whether my approach is the best approach, as I’m sure other veterinarians will as well. In the meantime, I urge you to speak to your veterinarian about what is best for your dog.
This article is posted and shared through the courtesy of the Pet Health Care Gazette