What is Lyme Disease? 

Lyme disease named for the town of Lyme, Connecticut, where the disease was first confirmed,  is caused by a spirochete bacterium called Borrelia burgdorferi. B. burgdorferi can infect numerous body systems including skin, muscle, joints, heart, eyes and nervous system and affects both humans and animals.

Clinical Signs: Clinical signs of Lyme disease are often vague and are similar to signs caused by other diseases. Some horses infected with B. burgdorferi will develop Lyme disease, while others will remain asymptomatic (no clinical signs).Clinical signs may include the following:

• Synovitis (swollen joints) 
• Neuroborreliosis, a rare form of Lyme disease can also present with fever, muscle wasting, difficulty eating, skin sensitivity and other neurologic signs 
• Uveitis (eye inflammation) 
• Skin masses or nodules at site of tick bite

Undocumented, but possible clinical signs include one or more of the following. Many other diseases are more likely causes of these clinical signs than Lyme disease: 

• Stiffness 
• Lethargy 
• Lameness 
• Change in behavior

Diagnosis: The diagnosis of B. borrelia infection and/or exposure is confirmed via measurement of serum antibody levels (titers). Horses with positive titers may have an active infection, or may have been infected in the past. It is important to remember that positive titers only indicate exposure, and do not confirm Lyme disease in horses with no clinical signs.

Treatment: In horses with clinical signs of Lyme disease, commonly used antimicrobial treatments include oxytetracycline intravenously, doxycycline orally, or minocycline orally. B. burgdorferi is also susceptible to ceftiofur. Treatment is NOT recommended for horses without clinical signs.

Prevention: Controlling exposure to ticks is needed to prevent infection.