04/10/2026
🦠 The clock is “ticking” as damp conditions and warmer temperatures in the Hudson Valley brings out the dreaded ticks. Lyme disease is transmitted by deer ticks. The deer ticks carry a spirochetal bacterium known as Borrelia burgdorferi.
🦠 Lyme disease is unfortunately slightly more complicated to both identify and diagnose, and in horses it is not as clearly defined as in other species (such as humans or dogs). Lyme disease typically does not present with a fever, and can be a more chronic malaise or subclinical syndrome. The known syndromes of lyme disease in horses include uveitis (inflammation of the eye), neuroborreliosis (neurologic lyme - which is RARE), nuchal bursitis and a more generalized disease causing swollen joints, lameness and stiffness. Other clinical signs that require more research include behavioral changes, muscle wasting, and hyperesthesia (sensitivity to stimuli).
🩸 Lyme disease is often overdiagnosed based on antibody testing, as many horses are exposed to lyme disease but do not actually manifest any clinical disease. It is important that your veterinarian be involved in the diagnosis and treatment of potential lyme disease as antibody testing alone does not rule in, or out the disease and other causes of general lethargy should always be investigated in conjunction. Oral treatment options includes a prolonged course of minocycline or doxycycline.
🩸The typical blood test we use is the Lyme multiplex assay at Cornell University. Per Cornell, "Lyme multiplex assay determines antibodies to three antigens, called 'outer surface proteins (Osp); of B. burgdorferi which have been shown to correlate with vaccinal antibodies, or acute and chronic stages of Lyme disease."
🩸Positive/ OspA (>2000 - 28,000): Positive values observed in vaccinated animals. In horses, however, antibodies to OspA also seems to rise during infection.
🩸Positive/OspC (>1000 - 10,000): Positive values for antibodies to OspC only are indicative for early infection.
🩸Positive/OspF (>1250 - 26,000): Positive values for antibodies to OspF only are predictive for chronic infection stages.
🌾Prevention is key, your horse should be checked thoroughly after each ride, and at least daily if they are out on pasture. Pasture management can also decrease the number of ticks your horse is potentially exposed to, and this can be in the form of removing brush and tall/long grass where ticks like to hide. Wildlife (such as deer) are also important vectors for tick introduction and deterring them from grazing areas can reduce the tick population.
💉Although an equine lyme vaccine isn’t available, we have used the canine Lyme disease vaccine off-label for many years with good results. Recent studies suggest that administering a higher dose of the vaccine results in the production of higher antibody levels. It is recommended to administer a "double dose" initial vaccination followed by a booster 3-4 weeks later. Thereafter the vaccine should ideally be given twice a year in early spring and late summer/early fall.
