Lyme disease Flashcards
What agent causes lyme disease?
Bacterial spirochete Borrelia burgdorferi
How is lyme disease transmitted?
Ticks
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Ixodes scapularis/ Deer Tick NE and North central US
- Horizontal transmission (larva > nymph > rodents)
- White-tailed deer maintain ticks (not competent hosts for B. burgdorferi)
- Ixodes pacificus and Ixodes neotomae in the Western US
- Do not infect host until attached for 24 hours (midgut > salivary gland)
What is the pathogenesis of lyme disease?
Migrate interstitially
- Extracellular organism lives near collagen and fibroblast (so no PCR)
- Incubation period 2-5 months (LONG) > generalized, systemic infection (connective tissue, joint capsules, muscles, lymph nodes)
What are the clinical signs in a dog with lyme disease?
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Most common form is subclinical
- In endemic areas, most healthy dogs are seropositive
-
Transient polyarthritis (most common clinical signs)
- Chronic, non-erosive arthritis
- Septic or immune mediated
- Systemic signs: anorexia, weight loss, lethargy, lymphadenomegaly
- Lyme-nephritis (uncommon)
- Golden and Labrador (30% Lyme arthritis)
- Protein Losing Nephropathy (so urinalysys) and acute progressive renal failure
- Histopathology: immune-mediated glomerulonephritis, tubular necrosis and interstitial necrosis
- Rare: myocarditis, CNS inflammation
- Study with experimental dogs
- 6-12 week old Beagle puppies sicker than adult dogs (no signs)
What lab work changes can you see in a dog with lyme disease?
- Leukocytosis with left shift
- Monocytosis
- Mild anemia
- NO THROMBOCYTOPENIA BECAUSE NOT SYSTEMIC
- Proteinuria
- Azotemia
- Joint > neutrophilic inflammation
What is the best way to diagnose a dog with suspected lyme disease?
Clinical signs + serology
-
ELISA and IFA
- Prevalence of seropositivity higher than prevalence of disease
- TOO sensitive > rule it out (subclinical infections, vaccines, non specific reactivity)
- Poor specificity
-
Western blot
- Can differentiate between vaccine vs. natural exposure if a sole antibody band is seen (sometimes not)
-
C6 peptide antibodies (can differentiate between disease and vaccine)
- SNAP test AND quantitaive (highly specific)
- Antibodies against C6 peptide (V1sE antigen)
- Appear 3 weeks post infection (lasts >70 weeks)
- Quantitative: some correlation of SEVERITY (titers > immunocomplexes); pre and post treatment
- NOT EXPRESSED IN VACCINES OR TICKS
Culture and PCR NOT USEFUL
How do you treat a patient with lyme disease?
Antibiotics: Doxyclycline (does not completely clear organism)
- 1 month for polyarthritis (improves in 2-3 days)
- Lymph nephritis: usually fatal, longer treatment
For proteinuria (lose antithrombin, etc. so also add aspirin)
- ACE inhibitors and renal diets
- For SEVERE renal failure, aspirin, spironolactone, immunosuppressive drugs (BAD, BAD, BAD)
People: Amoxicillin, Ceftraixone
How can lyme disease be prevented?
- Tick control (Advantix, Frontline, Seresto)
-
Vaccines + adjuvants ( decreases clinical signs)
- Single protein vaccines (OspA)
- Protect from infection and disease
- No clear infection: OspA > OspC
- Dual protein vaccines (OspA + OspC)
- Single and dual protein vaccine
- Consider for high risk dogs before tick season (immunity for at least 6 months)
- Not recommended for low endemic regions
- Single protein vaccines (OspA)
Asymptomatic dog, non-proteinuric, what do you do?
Ignore
Symptomatic dog lyme disease, non-proteinuric, what do you do?
Treat
Asymptomatic dog, proteinuric, what do you do?
Recheck (if severe, treat proteinuria and lyme disease)
Symptomatic dog, proteinuric, what do you do?
Treat proteinuria + lyme disease
Where (geographically) is lyme disease seen?
Worldwide distribution
- In the US:
- > 90% in the northeast, Minnesota and Wisconsin
- 4% in northern California
