Suspected clinical Lyme disease in horses: Serological and antigen testingdifferences between clinically ill and clinically normal horses from an endemic region

Equine Lyme disease is difficult to diagnose because of its nonspecific cli nical signs and the high incidence of subclinical infection in endemic regi ons, In this study we compared serology, antigen presence, hematology, bloo d chemistries and clinical presentation of 22 horses from a highly endemic region that were clinically diagnosed with Lyme disease to that of 21 clini cally normal horses from the same region, We found that horses clinically d iagnosed with Lyme disease were more likely to have Borrelia burgdorferi sp irochetal DNA in their blood and urine, have a higher percentage of positiv e immunoblots containing antibodies to certain B, burgdorferi proteins, and tend to have higher ELISA titers than healthy horses from the same region. These results may help to improve diagnostic testing for equine Lyme disea se.