Lyme disease is a multisystem tick-borne disease caused by infection with the spirochete Borrelia burgdorferi
. The spirochete is transmitted primarily during the blood meals of Ixodes
ticks. The disease occurs worldwide, following the same pattern similar to that of humans. There has been increasing incidences of Lyme disease reported worldwide, which are suspected to be caused by migratory birds and white-tailed deer.
The density of infected ticks is the primary factor for risk of infection with Lyme disease. Horses living in the northeast, midwest, and certain areas in California have a higher risk of infection.
Lyme disease in horses has been poorly documented and is not well understood. Infected horses often vary considerably in symptoms observed, and some horses don't show any symptoms. Lyme disease is most frequently associated with musculoskeletal disorders, including laminitis, swollen joints, muscle tenderness, and lameness.
The typical, early clinical signs of Lyme disease include weight loss, muscular atrophy, weakness, and laminitis -related. Symptoms usually progress to generalized stiffness with gait abnormalities, intermittent lameness, reduced ability to bend neck, fever, effusion and behavioral changes. Some horses develop marked muscle wasting, ataxia, depression, and severe neck stiffness.
Definite diagnosis is challenging unless ticks are found on the horse, or the horse is living in or has a history of visiting an area where infected ticks are endemic. Most cases of lyme disease occur during the spring and summer months.
The incubation period for Lyme disease in horses is not known, but it is 2–5 months in dogs and can be months to years in humans.