Justine Lee

The Diagnosis to Doubt: Lyme disease

Ah, Lyme disease. Not only is it the #1 mispronounced disease out there (it’s Lyme, not Lymes disease, folks!), but it’s probably also the #1 misdiagnosed disease as well. This Gram-negative spirochete (bacteria-like) organism Borrelia burgdorferi was originally discovered in Old Lyme, Connecticut in the mid-70s. Nowadays, over 90% of the cases of human Lyme disease come from Connecticut, Delaware, Massachusetts, Maryland, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island, and Wisconsin. Regardless of which state you live in, pay attention!
 
What is it?
Lyme disease, an infection that causes shifting-leg lameness, arthritis, joint swelling, fever, platelet abnormalities, and rare heart arrhythmias, is usually transmitted by the Ixodes deer tick (Ixodes scapularis or I. pacificus). In severe cases, it causes “Lyme nephritis,” which results in protein loss through the kidneys (called protein-losing nephropathy or “PLN”) and results in fatal kidney failure – this is particularly common in golden retrievers and Labradors.

How do I treat it?
Treatment for Lyme disease typically entails an antibiotic called doxycycline, which needs to be given for one month. While this is a relatively “safe” antibiotic, doxycycline can cause vomiting, esophagitis or reflux, sun-sensitivity, and permanent yellowing of puppy teeth – and it’s inactivated by dairy products – so make sure your dog really needs it before you give it!

Diagnosing Lyme
There are a lot of Lyme blood tests out there nowadays, and it’s important to know how these tests work. Thanks to a new convenient blood test called the Idexx SNAP ELISA 3DX or 4DX test, Lyme disease is probably a bit over-diagnosed and over-treated. Most vets use this test to check your dog for heartworm, but they don’t always know how to interpret the other two or three tests that come with it – which test for Lyme, Anaplasma and Ehrlichia canis – and that’s because we’re lacking adequate research data to tell us how it’s best to treat this confounding disease! The Idexx test detects infection or exposure to the Lyme bacterium (via an antibody called C6), and this test isn’t affected by vaccine-induced antibodies. In other words, if your dog was vaccinated for Lyme disease, this test won’t falsely test positive just because of the vaccine, unlike the old tests out there. If you’re looking for a more specific test, your vet can run a Western blot test (which can tell if a positive result is from true infection or Lyme vaccination;  a quantitative C6 from Idexx; or tick titers. Keep in mind that in some areas of the country, up to 90% of dogs may test positive while never demonstrating clinical symptoms of Lyme disease. So just because your dog tests positive doesn’t mean you necessarily need to treat them.

If your dog tests positive:
Relax. If this was done on the Idexx DX test, it means that your dog was exposed to the bacteria causing Lyme – but doesn’t mean that he’s going to develop symptoms and the disease. Take the next step and get a special urine test [testing for protein loss in the urine – specifically microalbuminuria - and a urine protein creatinine (UPC)] done. If this test is positive, or if your dog is showing symptoms of Lyme disease, then he should be treated. On the other hand, if you own a Labrador or a golden retriever, I’d be aggressive and recommend treating promptly – that’s because we want to ward off devastating Lyme nephritis. Otherwise, for your average Joe-dog, the positive test just means that at some point in his life, he’s been exposed to the bacterium causing Lyme, and he may not need treatment.

If your dog is negative:
Chances are that your dog doesn’t have Lyme and doesn’t need to be treated. If your dog is still showing signs of shifting leg-lameness, fever, etc., then your vet should hunt for something else going on, as it’s likely not due to Lyme – that is, unless it’s a very acute infection (and the body hasn’t had time to make antibodies to result in a positive test). Keep in mind that long-term treatment with doxycycline will eventually turn your dog’s test negative after a few months of treatment.

How to prevent it:
When in doubt, prevention is the key. I don’t typically recommend vaccinating for Lyme unless you live in one of the above mentioned states, own a hunting dog, or are hiking in the woods frequently. If you live in a deer-free area, or don’t live in a high-risk state, then your dog doesn’t need the Lyme vaccine. Instead, use preventatives like monthly prescription-strength tick preventative (like Frontline or Advantix). If you’re in a severely tick infested area, I also use these in conjunction with an additional Preventic collars too – especially if you have one of those predisposed breeds! When it comes to store brand tick collars – save your money. It’s not worth risking Lyme disease and potential kidney failure for a few dollars.

Easy ways to prevent Lyme disease in your pet:
•    Check your pet (and you!) carefully after a walk in the woods – check the inside thighs, the ears, and the trunk of the belly, where these tiny ticks like to hide.
•    Repeat your tick-inspection again the next day! It takes about 24-48 hours for a tick to transmit Lyme disease, so you have a narrow window to pull those ticks off.
•    Simply pull the tick off with a pair of tweezers as close to the base (skin) of the tick as you can.

Prevent side effects from Doxycycline by:
•    Double check to make sure the diagnosis is legit – and that your dog really needs these drugs in the first place!
•    Giving the pill in a small meatball, followed by your pet’s normal meal (to push the pill into the stomach)
•    Don’t give the pill right before your dog goes to bed – otherwise, it’ll make the esophageal reflux worse.
•    Keep your outdoor dog inside (so he’s out of the sun for long periods of time) while he’s on the medication.

Signing off tick free,

Dr. Justine Lee

References:
1.    Littman MP, Goldstein RF, Labato MA, et al. ACVIM small animal consensus statement on Lyme disease in dogs: Diagnosis, treatment, and prevention. J Vet Intern Med 2006;20(2):422-34.

Biography:
Justine Lee, DVM, DACVECC is a veterinary emergency critical-care specialist and the associate director of veterinary services at Pet Poison Helpline. She is the author of It’s a Cat’s World…You Just Live in It and It’s a Dog’s Life… but It’s Your Carpet.