Serological survey for antibody to Encephalitozoon cuniculi in horses in the USA

Encephalitozoon cuniculi is an obligate intracellular microsporidian parasite that can result in clinical and subclinical infection in many species. In the present study, a serological survey was conducted using samples from 105 horses in the state of New Jersey; 49 of the samples were obtained from clinically abnormal animals. Five or 4.8% of 105 serum samples were found to demonstrate reactivity by ELISA with titers of 1:64 to 1:1,024. One of the samples was obtained from a clinically normal horse. Clinical signs and diagnoses from the other animals included lameness, colic, osteochondritis dissecans, and fever. All clinical issues were resolved with hospitalization and treatment without the institution of E. cuniculi-focused therapy. This is the first report on the detection of E. cuniculi antibodies in horses in the USA.