Borrelia Flashcards
Characteristics of Borrelia
Gram-negative loosely coiled spirochete
Commonly cause arthropod (usually tick) borne infections
Grow slowly in specialized media (microaerophilic)
Have linear chromosome
Borrelia burgdorferi
Lyme disease
Transmitted by Ixodes tick
Under reported and over diagnosed disease
Virulence factors of borrelia
Antigenic variation in major outer surface lipoproteins (OSP)
Osp C to Osp A in midgut of ticks and in culture
Osp A to Osp C in salivary gland of tick
Osp C in mammals in early infection
Lyme disease transmission
Ticks become infected when feeding on animal with high level of bacteremia
Spirochete up-regulates expression of an outer surface protein, which is essential for virulence in mammals
Spirochete moves from midgut to hemolymph to salivary glands
Transmission of spirochete requires around 50 hours
Lyme disease pathogenesis
Spirochetes multiply to highest numbers in the skin and disseminate via the bloodstream Skin rash (erythema migrans) is often the first sign of infection in humans
Canine lyme disease
Infection is usually subclinical
Typical clinical signs in dogs are fever, acute arthritis, aarthralgia, and lameness
Sometimes anorexia, lethargy, and depression
Diagnosis of lyme disease
SNAP test - point of care test
Western Blot
Multiplex ELISA
How to interpret results for a lyme disease diagnostic test
Clinical signs and positive titer = Infected
Healthy and negative test = Not infected
Clinical signs and negative test = Evaluate for underlying disease, retest
Healthy and positive test = Likely to be infected subclinically
Treatment of lyme disease
In endemic area treatment is preferred, in non-endemic areas treatment is usually not pursued
Doxycycline
Vaccination for lyme disease
Antibodies against Osp A antigen on organisms present in midgut of ticks
Vaccine may block transmission by interfering with Osp A to Osp C conversion
Antibodies produced int eh dog must be delivered to the tick to exert this effect
