Experimental infection with equid herpesvirus 3 in seronegative and seropositive mares

Equine coital exanthema (ECE), caused by equid herpesvirus 3 (EHV-3), has been recognized as an economically significant venereal disease for years. However, no infection models on the natural host have been established. In order to set up an experimental infection protocol, seronegative and seropositive mares were topically inoculated in the perineal region with 4 × 106 TCID50/ml of EHV-3. Clinical signs were then evaluated by means of a designed scoring system, and body temperature was recorded daily. Virological, and serological studies were also performed. Typical ECE lesions, with clinical scores of 90, 92, 160 and 172, were observed in the four seronegative animals. Only mild ECE lesions were observed in the two seropositive mares, being the clinical scores 53 and 41. Both groups of mares shed the virus, but the duration of virus shedding was shorter and its intensity was lower in seropositive mares than in seronegative ones. Moreover, EHV-3 antibody response was detected in both seronegative and seropositive mares after experimental infection and re-infection, being more moderate in seropositive ones.As a conclusion, EHV-3 infection of mares was experimentally achieved in a reproducible manner. The typical lesions of ECE were observed after topical EHV-3 infection in seronegative mares, in association with virus excretion and neutralizing antibody kinetics.