The Lyme controversy

This morning at grand rounds, the room was more crowded than I have ever seen it. Every Friday morning, from 8-9 am, a resident or intern presents on a particular topic. People come if they are interested and if they are free. I have seen grand rounds have as few as a dozen people in attendance. There must have been at least fifty today. I have seen rounds where no one asks a question. There were about a dozen questions asked today. The resident closed her talk with a picture of boxing gloves and announced, “This is a controversial topic, so let’s keep our gloves on while we ask questions, okay?” The topic was Lyme disease.

What is Lyme disease?
Lyme disease occurs in humans and dogs, though it presents differently in the two species. (Cats don’t get clinical signs of Lyme.) The disease is caused by a bacteria called Borrelia burgdorferi. The disease is often not serious, with clinical signs like lameness, loss of appetite, and lethargy. These signs are usually resolved after a course of antibiotics, usually doxycycline.

However, Lyme is associated with Lyme nephropathy, a disease of the kidneys which can be fatal. This is a less common outcome, but a very serious one.

Lyme has been studied in laboratory dogs. However, Lyme nephropathy appears to occur most often in Labrador retrievers and golden retrievers; it is possible that they have a genetic predisposition for it. So what we have learned in laboratory dogs (who are almost exclusively Beagles) may or may not apply to retrievers.

Should I vaccinate my dog for Lyme?
This is the first part of the controversy. Different veterinarians have different answers for you.

Some say: Yes! The vaccine is very safe and effective. The possibility of Lyme nephropathy makes any risks associated with vaccination to be well worth taking.

Some say: No! We don’t actually know that Borrelia causes Lyme nephropathy. Some people suspect that it may in fact be associated with the Lyme vaccine. Moreover, 95% of dogs who are exposed to Borrelia never develop any clinical signs. In other words, they never become sick. The few who do develop clinical signs are almost always easily managed with antibiotics. Why take a chance with a vaccine, which may have side effects, when the chances that your dog will develop Lyme nephropathy are so low?

My dog is Lyme positive. Should I treat him with antibiotics?
If your dog shows signs of lameness, fever, lethargy, and has a positive Lyme titer, then definitely he should receive a course of antibiotics. (Of course, a vet will rule out any other likely diagnoses first.)

What if your dog shows no clinical signs? This is the second part of the controversy.

Some say: Yes, the dog should be treated. Otherwise, he is at risk of eventually developing Lyme nephropathy. Best not to risk that.

Some say: No. The likelihood is that the dog will never develop any clinical signs (that he will remain healthy). We don’t actually know, again, that Lyme nephropathy is actually “Lyme” nephropathy. Antibiotics are not 100% safe, and may have side effects. Administration of them may lead to antibiotic resistance. Additionally, most dogs who are treated for Lyme with antibiotics maintain a positive titer for Borrelia after treatment is concluded. In other words, their immune system continues to produce antibodies against the bacteria, suggesting that they still have Borrelia in their systems, despite treatment (though presumably lower levels of it). We may actually be breeding resistant strains of Borrelia in our own dogs by treating unneccessarily. Again, 95% of dogs who have positive Borrelia titers never develop signs of the disease.

It is possible (and probably a good idea) to monitor Lyme-positive dogs by periodically checking their urine for extra protein (“proteinuria”). This is a sign of kidney issues. Even this is up for debate, though, as the test can be expensive and it’s not clear how often it actually catches a problem.

One interesting point made during the discussion at the end of the lecture was from an IDEXX representative. She said that a veterinarian had told her that he routinely treated Lyme-positive dogs, and on re-testing found their Lyme titers to be reduced. A faculty member pointed out in response that as no control group had been tested, it is possible that Lyme-positive dogs see titer reductions after some period of time anyways.

What do I do?
My dog, Jack, tested positive for Lyme this past spring for the first time. There are indeed plenty of ticks in my back yard (though I do my best to manage them with frequent mowing). His positive Lyme titer means that he has “seen” the disease — been bitten by a tick which carries Borrelia. His immune system has responded appropriately, making antibodies to the bacteria. He shows no clinicial signs; his appetite is excellent, and he is no more lethargic than any other aging golden retriever. I had his urine tested; he has normal protein levels. I have not treated him with antibiotics.

References
I’m reporting what I learned in this morning’s talk from memory. I hope that I did not misreport any facts, but please take all statements with a grain of salt, as I have only completed two years of veterinary school.

For more information, see:

• 
  Consensus statement on Lyme from the ACVIM (American College of Veterinary Internal Medicine)


• Q&A with a veterinarian about Lyme


• 
  Information page about Lyme from the College of Veterinary Medicine at Washington State University