Canis ISSN: 2398-2942

Borrelia burgdorferi

Introduction

Classification

Taxonomy

• Family: Spirochaetaceae.
• Genus: Borrelia.
• Species: burgdorferi.

Active Forms

Clinical Effects

Epidemiology

Habitat

• Ticks which carry Borrelia are found in wooded areas.
• Reservoir in ixodid ticks and mammalian reservoirs such as deer and rodents.

Lifecycle

• Two year lifecycle.
• Four distinct developmental stages and three hosts are required.
• Transtadial transmission in ticks occurs.
• Tick larvae emerge in spring → infected by feeding on infected mice.
• Larvae drop off and enter resting stage until following spring → molt to nymphal stage.
• Nymphs feed for 3-4 days on new host → host becomming infected with spirochetes.
• Nymphs drop off and molt to adult stage.
• Adults feed for 5-7 days on large mammals.
• Females overwinter and lay eggs the following spring.

Transmission

• Tick bite - Ixodes spp are the arthropod vectors; species depends on the geographical location, eg in Europe, the tick involved is Ixodes ricinus.
• In the US, Ixodes dammini and Ixodes pacificium are the principle vectors.
• Rodents are reservoir hosts.
• Canine and feline infections are not considered zoonotic.
• Tick must be attached for several hours before infection of host occurs.

Pathological effects

• Immune complexes and immunosuppression are thought to be involved in the pathogenesis.

• Endotoxin is probably involved in the pathogenesis.
• Dog: acute polyarthritis, classically migratory, chronic, recurrent, intermittent, non-erosive arthritis Arthritis: borrelial , glomerulonephritis Glomerulonephritis.
• Cattle: abortions.
• Horse: arthritis, uveitis, encephalitis, ocular, neural involvement and death in foals.
• Man: skin rash (erythema migrans), sometimes arthritis, neural, cardiac sequelae.

Control

Control via chemotherapies

• Amoxicillin Amoxicillin.
• Tetracycline Tetracycline.
• Azithromycin Azithromycin and ceftriaxone may be used in refractory cases.
• Treatment regimes depend on the nature and severity of clinical signs but should be continued for minimum of 30 days.
• Tetracycline treatment reduces the relapse rate.

Control via environment

• Chemical control of tick populations in endemic areas has been relatively successful.
• Daily removal of ticks from dogs and cats can be beneficial as ticks must feed for 2-3 days before disease transmission occurs.

Vaccination

• Killed bacterin, OSpA vaccines available in the USA; primarily used in endemic areas.

Diagnosis