Lyme borreliosis (LB), also known as Lyme disease, is a tick-transmitted inflammatory disease induced by spirochetes. In dogs, the infection is common in the moderate climate regions of the Northern Hemisphere; prevalence of infection in dogs may range regionally as high as 85%, but generally is approximately 3 to 10%.
The infection is zoonotic, and LB in humans is the most important reported vector-borne disease in Europe and the USA. The human disease was first identified in the North-Eastern part of the USA in the town Lyme during the 1970s, but retrospective analysis revealed its presence since the late 19th century in Europe and the US.
At least three closely interrelated elements must be present in nature to spread LB:
(1) the Lyme borreliosis-causing bacteria of the Borrelia burgdorferi sensu lato (s.l.) complex,
(2) Ixodes ticks as transmitting vectors for the pathogens, and
(3) mammals (e.g., mice and deer) that provide a blood meal for the ticks through their various life stages.
Although a high proportion of dogs are positive for specific antibodies in endemic areas, not all infected animals develop clinical signs. Therefore, diagnosis should be based on both, clinical signs and serologic testing. Therapy consists of antibiotic treatment for four weeks. Vaccines are available for the USA and other countries.
Treatment and Prevention
The genus Borrelia is included in the bacterial family Borreliaceae within the order Spirochaetales. The spirochete, isolated from ticks and humans, was identified as Borrelia by Willy Burgdorfer, et al. in 1982. In Europe, clinical signs of human borreliosis were described in patients for the first time by Afzelius in 1910 and by Lipschütz in 1913.
There are at least 52 Borrelia species, including 21 in the Lyme borreliosis (LB) group (Borrelia burgdorferi sensu lato [s.l.], gram-negative spirochetes which generally migrate interstitially within the host), 29 in the relapsing fever group (migrating haematogenously), and 2 undetermined members.
In dogs in North America, LB has only been associated with Borrelia burgdorferi sensu stricto (s.s.), of which several subtypes or strains exist, based on outer surface protein C (OspC, Osp=outer surface protein) genotyping. In Europe, coinfections of B. burgdorferi sensu stricto (s.s.) with other B. burgdorferi s.l. strains (i.e., Borrelia garinii) may predispose dogs to illness. Other B. burgdorferi s.l. species causing human LB (i.e., Borrelia mayonii in upper Midwestern states in the U.S.; Borrelia afzelii, Borrelia bavariensis, B. garinii, and Borrelia spielmanni in Europe) are not known to cause illness in dogs so far (Littman et al., 2018).
Two of the outer surface membrane proteins, OspA and OspB, are antigenic and useful in differentiating these organisms from other spirochetal species.
Darkfield microscopical image of helical shaped Borrelia burgdorferi bacteria (about 10-25 µm length)
B. burgdorferi can be cultivated from its arthropod vectors or vertebrate hosts in Barbour-Stoenner-Kelly (BSK II)-medium. Here especially Borrelia from ticks and skin biopsy samples have been successfully cultivated. B. burgdorferi grows slowly as compared to most other bacteria. Cultivation of Borrelia is very difficult, because of a long time needed for development (6-8 weeks) and a medium which also supports the growth of other bacteria and fungi, potentially reducing or even blocking Borrelia growth. Thus a sterile sampling technique is of major importance.