Lyme Disease

Lyme disease is caused by Borrelia burgdorferi, a bacterium transmitted through the bite of infected Ixodes ticks (the deer tick or castor bean tick). In the UK, Ixodes ricinus is the primary vector. Not all ticks carry Borrelia - infection rates in UK tick populations vary by region, with higher prevalence in areas where deer and small mammal populations support the tick life cycle.

The tick must be attached for approximately 24–48 hours before transmission occurs. This is why regular tick checks and prompt removal remain important even for dogs on tick-preventive treatments.

UK distribution

Lyme disease risk is highest in:

• Scotland (particularly the Highlands)
• South West England (Exmoor, Dartmoor, the New Forest)
• Parts of Wales
• Wooded and moorland areas across England

Urban and suburban parks can also harbour infected ticks where wildlife moves through them.

Clinical signs in dogs

Most dogs exposed to Borrelia don't develop clinical disease. Those that do typically show signs 2–5 months after infection - the delay is why connecting clinical signs to a specific tick exposure is difficult without a log.

Classic signs of Lyme disease in dogs:

• Lethargy and fever: Often the first signs. The dog seems unwell without obvious cause.
• Shifting leg lameness: A characteristic feature - lameness that moves from leg to leg over days, without a consistent pattern. Often intermittent and may spontaneously improve and return.
• Joint swelling: Affected joints may be warm and swollen during a lameness episode
• Reduced appetite
• Lymph node enlargement

A less common but serious complication is Lyme nephritis - immune-mediated kidney disease triggered by the infection. This is potentially fatal. Signs include increased thirst, urination, vomiting, weight loss, and lethargy - sometimes without the preceding musculoskeletal signs.

What to log

For dogs in tick-risk areas, log:

• Tick finds and removals: Date, location on the body, estimated attachment duration (engorged vs. flat)
• Tick prevention product: Name, date applied or given, and whether the current product is up to date
• Any unexplained lethargy, fever, or lameness: Particularly if shifting or intermittent
• Walking locations: Particularly woodland, moorland, or heathland areas

This log becomes critically important if Lyme disease signs develop. A vet who knows your dog walked on Dartmoor three months ago and has now developed shifting lameness can put those pieces together.

Diagnosis

Diagnosis is by:

• C6 antibody SNAP test (in-clinic): A rapid test detecting antibodies to the C6 protein. Positive in approximately 3–5 months after infection. Does not confirm active disease but indicates exposure.
• Quantitative C6 test (laboratory): Measures antibody level; used to assess treatment response
• Western blot: Confirmatory testing in uncertain cases

Urine analysis to assess renal protein loss should be performed in any Lyme-positive dog to rule out Lyme nephritis.

Treatment

Antibiotic treatment: Doxycycline is the first-line treatment - typically 4 weeks. Most dogs respond well, with improvement in lameness and energy within days. After treatment, C6 antibody levels are monitored to confirm response.

Lyme nephritis: If detected, requires aggressive management - ACE inhibitors, dietary modification, immunosuppressants in some cases. Prognosis is guarded to poor.

Prevention

Tick control is the most important preventive measure:

• Prescription tick treatments (oral isoxazolines or spot-ons with tick-killing activity) significantly reduce tick attachment duration and kill ticks before transmission can occur
• Post-walk tick checks remain important - find and remove any attached ticks promptly with a tick hook
• Prompt removal matters: transmission requires 24–48 hours of attachment

Vaccination: A Lyme disease vaccine (Nobivac Lyme) is available in the UK for dogs in high-risk areas. It is not a core vaccine but is recommended by some vets for dogs regularly walking in high-risk areas.

When to contact your vet

Contact your vet soon if:

• Your dog has unexplained lethargy, fever, or shifting lameness
• A Lyme test has been positive and treatment hasn't been started
• Any dog in a high-risk area developing signs consistent with Lyme disease

Contact your vet promptly if:

• A Lyme-positive dog develops increased thirst, urination, or vomiting (potential nephritis)

Frequently Asked Questions

My dog tested positive for Lyme - does that mean they're currently ill? Not necessarily. A positive C6 antibody test means the dog has been exposed to Borrelia and mounted an immune response. Many exposed dogs are clinically normal. The quantitative C6 level and clinical signs together determine whether treatment is indicated.

Should all dogs in the UK be vaccinated against Lyme disease? Vaccination is most appropriate for dogs regularly walking in known high-risk areas (Scottish Highlands, Exmoor, New Forest, and similar environments). It's a conversation to have with your vet based on your dog's lifestyle and walking locations.

I found a tick on my dog. Should I be worried about Lyme disease? If the tick was found promptly and removed before 24 hours of attachment, transmission risk is low. If the tick was engorged (indicating prolonged attachment), monitor for signs of illness over the next 2–3 months and mention it at your next vet visit.

Can I catch Lyme disease from my dog? Your dog cannot directly give you Lyme disease - the bacteria require a tick bite to transmit. However, a dog that brings ticks into the home increases the risk of ticks biting people. Check yourself after walks in tick-risk areas, particularly around the scalp, groin, and armpits.

Is Lyme disease common in urban dogs? Much less so than in rural dogs. The tick vector (Ixodes ricinus) requires woodland or heathland habitats and the appropriate wildlife hosts. Well-managed urban parks pose much lower risk than moorland, forestry, or heathland.