Borreliosis (Lyme Disease): Dogs

(Canine Lyme Disease)

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Borreliosis (Lyme disease)

 Clinical Signs & Symptoms

Subclinical infection is common in dogs. When chronic infection does develop in individual dogs, it may persist for several years. In addition, re-infection or co-infections with other tick-transmitted organisms may occur. When clinical disease occurs, the most common signs are:

  • Lethargy (weakness / loss of energy)
  • Anorexia (loss of appetite leading to weight loss)
  • Pyrexia (fever)
  • Inflammatory arthritis – maybe mono- or polyarthritis (single or multiple joint involvement)
  • Lymphadenopathy (swollen / enlarged lymph nodes)

In rare cases, renal (kidney), cardiac (heart), and neurologic forms of the disease can develop. Renal Borreliosis (also known as Lyme nephritis) is generally fatal. It is characterised by severe kidney problems, and abnormalities can include uremia, hyperphospataemia, and severe protein-losing nephropathy, often accompanied by peripheral oedema. In the cardiac form, conduction abnormalities with bradycardia (slow heart rate) can occur. In the neurologic form, paralysis and seizure disorders have been reported.

There is little information available regarding incubation periods for naturally infected dogs. However, joint disease following experimentally-induced infection presents after two to five months. The first episode of arthritis is generally in the limb closest to the tick bite. In untreated or inadequately treated dogs, episodes of arthritis and lameness may be recurrent. In humans, the different species of Borrelia bacteria induce differing clinical signs, but it is currently unknown whether this is the case in dogs.

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There is still debate within the veterinary community as to what constitutes a definitive diagnosis of canine Borreliosis. This is because of the subjectivity of criteria used in defining the naturally occurring disease. Diagnosis should be based on history, clinical signs, elimination of other diagnoses, laboratory data, epidemiologic considerations, and response to antibiotic therapy.

Clinical laboratory findings are non-specific for canine Borreliosis. Abnormalities present on blood and urine tests may include:

  • An inflammatory leucogram (elevations in white blood cells)
  • Renal azotaemia (kidney failure)
  • Hypoalbuminaemia (decreased levels of albumin in the blood)
  • Proteinuria (protein present in the urine)
  • An inflammatory urine sediment (evidence of kidney inflammation)
  • Joint fluid changes include an increase in cell counts that consist primarily of a neutrophilic response.

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Diagnostic Tests

Tests can be divided into two categories:

1. Tests which detect the Borrelia organism directly

Borrelia burgdorferi is only transiently present in circulating blood and whole blood is not considered a useful diagnostic specimen for evaluation of infection. Spirochetes may reportedly be found in synovial fluid using dark-field microscopy, but low numbers of organisms are present in clinical specimens, precluding direct visualisation. Although organisms have been reportedly identified in peripheral blood, urine, joint and CSF fluids by use of dark-field or phase-contrast microscopy in naturally and experimentally infected dogs, these techniques are not generally used in clinical practice.
Cell culture isolation requires specialised media and is challenging because of the relatively low density of organisms present in chronic infections.

Polymerase chain reaction (PCR) based tests, which are more sensitive, are also available to detect the organism in tissue samples.

2. Tests which measure antibodies against Borrelia

These include the indirect fluorescent antibody (IFA) assay, enzyme-linked immunosorbent assay (ELISA), or characteristic serum proteins analysis (Western blot technique).

Serology is the mainstay for confirming a clinical impression of Lyme disease. However, asymptomatic dogs in endemic areas may often be seropositive. Another limitation is that animals can take some time to seroconvert following infection. Therefore, many early cases can return a negative result on serology. Animals may also remain seropositive for a long time following treatment, making it difficult to determine whether a successful resolution has been achieved.

Many veterinarians consider the specific C6-based assay to be the initial screening method of choice for evaluating a dog for exposure to, and potentially infection with, Borrelia burgdorferi.

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The standard treatment for disease in dogs is the antibiotic doxycycline PO @ 10mg/kg q24h for 30 days.

Rapid response is seen in limb and joint disease in most cases, although incomplete or transient resolution of signs occurs in a significant number of affected animals.

Due to the persistence of B. burgdorferi sensu lato, relapses can occur. Two different experimental studies of experimentally-infected dogs revealed that a 30-day course of therapy with amoxicillin, doxycycline, ceftriaxone and azithromycin failed to eliminate infection, though it did reduce the ability of investigators to isolate the organism from tissues. Longer courses of treatment may be necessary, particularly in dogs with nephropathy (kidney disease).

In cases of relapse, antibiotic treatment may be repeated as persistent infection is not the result of acquired antibiotic resistance. Prolonged antibiotic therapy (over 30 days) may be beneficial in certain cases with continuing disease signs.

Symptomatic therapy directed toward the affected organ system and clinicopathologic abnormalities is also important, especially in renal disease. In limb and joint disease, the use of NSAID (non-steroid anti-inflammatory drugs) concurrent with antibiotic therapy can lead to confusion over the source of clinical improvement and make diagnosis based on therapeutic response difficult.

Antibiotic treatment of clinically normal but seropositive dogs is controversial. Many seropositive dogs do not display evidence of clinical disease. However, because the course of infection can be prolonged, treating in the subclinical phase is viewed by some veterinarians as potentially beneficial in preventing the development of chronic disease.

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Medical Abbreviations

by mouth
every 8 hours
every 12 hours
every 24 hours

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A vaccine to protect dogs against Lyme disease has recently become available in the UK and Ireland. Ask your vet for more information about having your dog vaccinated.

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