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Diagnosis and treatment of Borrelia burgdorferi
infection in dogs |
Diagnosis of LD in dogs:
Serology:
- IFA
- ELISA is now more commonly used for screening
- Western blot [Qualicode®/Immunetics] may be more specific
for confirmation, looking for a strong band corresponding to
ospA immunoreactivity in vaccine recipients that is generally
missing in naturally infected individuals, and additional bands
in the infected animals that can not be accounted for by vaccination.
- A similar combination of ELISA screening and immunoblot confirmation
is also recommended in humans.
- A new ELISA format using a short peptide (C6) in place of
the whole organism has recently been developed and appears to
be both sensitive and specific, able to differentiate infected
from vaccinated dogs, and possibly able to assess response to
antibiotic therapy.
But serodiagnosis of LD is very problematic!
- Many studies have shown that the rate of seropositivity in
enzootic areas is much higher than the prevalence of clinical
disease and sero (+) status in clinically normal dogs from enzootic
areas is a very poor predictor of future development of clinical
LD.
- IgM cannot necessarily be used as an indicator of recent
infection because IgM titers remain elevated in dogs for prolonged
periods of time after infection.
- Serology cannot be conclusively used to monitor response
to therapy because Ab titers tend to remain elevated after antibiotic
treatment.
PCR:
- A PCR-based diagnostic test is becoming more widely available.
Culture:
- The organism is very difficult to grow in culture, so specific
isolation is not generally practical on a routine basis in veterinary
medicine. However, culture from skin biopsy specimens is sometimes
undertaken in humans.
Treatment of B. burgdorferi infection in dogs:
- amoxicillin (20 mg/kg, q8h, 30 days)
- doxycycline (5-10 mg/kg, g12h, 30 days)
- As in humans, routine oral antibiotic therapy may not be
consistently effective in completely clearing all of the B.
burgdorferi organisms from the body. B. burgdorferi
can persist in skin, CNS, joint and connective tissues. People
with advanced disease (early disseminated disease with heart
block or late disseminated disease) are often treated with 14-28
day courses of IV ceftriaxone.
Should all exposed (evidence of tick bite) animals
be treated prophylactically with antibiotics?
- This question remains controversial and the data from human
studies are conflicting. In one study, the risk of infection
was not significantly different between antibiotic- and placebo-treated
tick bite patients, while another study showed a positive effect
of antibiotic treatment, but only if the risk of infection in
an area was >3.6% of tick-bitten individuals. The appropriateness
of prophylactic treatment may also be dependent on a clinician's
ability to recognize different tick species.
- In enzootic areas, it is probably unreasonable to consider
treating all dogs that are found to have been bitten by a deer
tick, since this is almost a daily occurrence for those that
spend time outdoors!
