07/07/2026
According to the AAEP's 2025 publication Borrelia Burgdorferi Infection and Lyme Disease Guidelines, “Many horses infected with B. burgdorferi will remain asymptomatic and never develop clinical disease, and it is generally considered that infection is common, but clinical Lyme disease is rare.”
And yet, equine practitioners report that owners frequently believe their horses are showing signs of Lyme disease. Clinical signs owners attribute to Lyme disease predominantly include general malaise, stiffness, and lameness but might also include weight loss, low-grade fever, muscle tenderness, and poor performance.
While it’s possible that Lyme disease causes these signs, the AAEP states that only limited evidence exists supporting lameness as a clinical sign. Instead, documented syndromes attributable to Lyme disease include neuroborreliosis, cutaneous pseudolymphoma, nuchal bursitis, and uveitis.
The 2018 ACVIM Consensus Statement on B. burgdorferi further states, “The association of B. burgdorferi infection with stiffness and lameness in horses is not well documented, and there is no evidence of the infection causing laminitis. … The actual range and specific clinical signs associated with Lyme disease needs further experimental and epidemiological evaluation.”
Read more in this article: https://equimanagement.com/research-medical/disease/are-we-overdiagnosing-lyme-disease-in-horses/
