Although a high proportion of dogs may be seropositive in endemic areas, not all intervals develop clinical signs. Rashes (erythema migrans) are rarely found in dogs and may not be readily apparent on dogs. Those that occur are localised and transient.
The incubation period for naturally infected dogs is not known. In a laboratory model, the humoral immune response developed within 4 to 6 weeks and clinical signs such as fever spikes and shifting leg lameness developed after 2 to 5 months. Lameness only lasted 3 to 4 days without treatment but recurred at 2 to 4 week intervals in 60% of the dogs. Recurrences occurred commonly for 2 to 3 episodes, then resolved. However, histologic examination of tissue samples revealed lesions due to inflammatory responses (mild polyarthritis) more than one year after infection had occurred.
Acute clinical signs most commonly reported include fever, shifting leg lameness, lethargy, lymphadenopathy, and general malaise. Additionally, several distinct clinical symptoms may be recognized including polyarthritis and protein-losing nephritis. Other symptoms reported involve carditis, and neurologic abnormalities. While lameness is a common clinical sign in canine Lyme borreliosis, the almost crippling, non-antibiotic responsive, chronic arthritis as in humans is rarely seen.
Clinical signs in humans
Human Lyme disease symptoms resemble many other diseases, like spirochete-caused syphilis. Three stages of infection can be distinguished: erythema migrans usually within the first month and often combined with flu-like symptoms, early dissemination of infection especially combined with lameness and the late disseminated disease after months to years associated with chronic changes in joints, skin and nervous system.
- Appel MJG: Lyme disease in dogs. Comp Cont Educ Pract Vet. 2002, 24 (Suppl.), 19-23
- Fisher M, McGarry J.: Focus on Small Animal Parasitology. 2006, Kingfisher Press Limited, London
- Shaw SE, Day MJ, Birtles RJ, et al.: Tick-borne infectious diseases of dogs. Trends Parasitol. 2001, 17, 74-80