A Positive Lyme Test in a Healthy Dog
Most dogs that test positive for Lyme never get ill. What a positive screen means, why specialists split on treating, and the urine test that matters.
Written by thecanineledger
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“Most Bb‐seropositive dogs show no clinical signs.” That’s the American College of Veterinary Internal Medicine’s 2018 consensus on Lyme disease in dogs and cats (Littman et al., J Vet Intern Med 2018). Bb is Borrelia burgdorferi, the bacterium that causes Lyme disease. Seropositive means the dog has antibodies to it.
A positive test shows a dog has been bitten by an infected tick. It doesn’t mean the dog is ill. The consensus notes that “most dogs that are exposed seroconvert, but do not develop clinical illness”.
While a positive result is worth acting on, the action usually isn’t antibiotics. This page explains why specialists disagree about treating healthy dogs, and the follow-up test they all agree on.
1. Why healthy dogs get tested
In North America, the ACVIM panel recommends screening “all healthy dogs that live in, live near, or travel to Bb‐endemic areas”. It gives several reasons. A positive result prompts a urine check for kidney problems. It shows tick exposure, so ticks may be carrying other infections too. And it can show whether tick prevention is working.
The panel also lists the downsides of screening: overuse of antibiotics in dogs “that would never develop LB” (Lyme borreliosis), the cost, and “induction of anxiety in the owner”.
2. The urine test
The panel agreed that every positive dog should be checked for protein in the urine: “It is recommended to screen all Bb‐seropositive dogs for proteinuria”.
That’s because the most serious form, Lyme nephritis, damages the kidneys. It’s uncommon. The panel notes that proteinuria is “seen in <2% of Bb‐seropositive dogs.”
North American panellists recommend rechecking urine “at least 2–3 times per year”, even if the dog has had antibiotics.
3. To treat or not
This is where specialists split. The panel calls the question “still controversial”, and “4/6 panelists do not routinely recommend treatment” for healthy dogs with normal urine. Their reasons:
- It may encourage overuse of antibiotics.
- “no data exists proving treatment of healthy dogs is associated with decreased risk of illness”.
- Treatment may not clear the bacterium from every tissue.
- Dogs in tick areas are often reinfected.
The panel also notes that “the vast majority of Bb‐seropositive dogs never become ill nor proteinuric”. One panellist favours treating healthy dogs with high antibody levels, but the consensus says there’s no evidence those levels help decide.
Our note: The consensus is from 2018. We haven’t checked for newer evidence.
4. Signs that do need a vet
The main forms of illness are Lyme arthritis, which causes lameness, and the less common Lyme nephritis. The consensus says signs of Lyme arthritis “are transient or respond quickly to PO antibiotics” (by mouth).
See your vet if a dog that tested positive becomes lame, stops eating, or seems unwell. Kidney disease can cause drinking and urinating more, vomiting, or weight loss. → Chronic Kidney Disease: What the IRIS Stage Means
Our note: The kidney signs are general signs of kidney disease, not taken from the Lyme consensus.
5. What to ask your vet
- Was this a screening test, and which one?
- Has my dog’s urine been checked for protein? When should we recheck?
- Do you recommend antibiotics for my dog, and why?
- Is my dog’s tick prevention working, and should it change?
- Could my dog have picked up other tick-borne infections?
Our note: The consensus is written for North America. Lyme in Europe involves different Borrelia species, and screening advice differs.
6. What we could not verify
| Commonly said | What we found |
|---|---|
| “A positive test means my dog has Lyme disease” | No. Most positive dogs never become ill. |
| “Every positive dog needs antibiotics” | Not agreed. Four of six panellists don’t routinely treat healthy dogs. |
| “Antibiotics clear Lyme for good” | Not shown. The panel says the bacterium may not be cleared. |
| “A high antibody level means my dog will get ill” | No. The consensus says the level “is not predictive of illness.” |
Sources
- Littman MP, Gerber B, Goldstein RE, Labato MA, Lappin MR, Moore GE. ACVIM consensus update on Lyme borreliosis in dogs and cats (J Vet Intern Med 2018; specialist consensus statement; full text read; authors declare industry collaborations, listed in the paper)
Always confirm with your vet before acting on anything on this page.