Viral respiratory infections are common in horses, notably equine herpesvirus infection and equine influenza, which primarily initiate secondary bacterial respiratory infections such as strangles caused by Streptococcus equi equi. A decline in the production of stallions has been associated with these respiratory diseases leading to adverse financial implications. This study investigated the antibody responses against respiratory diseases in horses from Jeju Island a year after vaccination. A low level of equine herpesvirus type 1 (EHV-1) (11.36%) antibodies was detected from stallions, however a high level of EHV-4 (95.84%) antibodies was detected from horses without vaccination against this infection suggesting that EHV-4 is ubiquitous in this horse population. In case of equine influenza, ranch stallions showed low positive rate (12.06%) whereas stallions from Subtropical Livestock Research Institute displayed higher positive rate (81.32%). Antibody responses against equine influenza and strangles revealed positive rates of 26.32% and 55.12%, respectively. These findings may draw attention towards the importance of developing an improved disease prevention and/or immunization program that will effectively control respiratory diseases in horses.

Respiratory diseases among horses cause economic losses in foals and productivity decreases in horses being raised and in adult horses. In South Korea, fundamental studies of horses’ respiratory diseases and those related to disease occurrence are insufficient. Therefore, the aim if the current study was to use diverse hematological indicators, obtained through hematological tests and measurment of blood antibody level in horses suffering form respiratory diseases, to monitor disease occurrence and prognosis evaluation. Investigations of infection states by horses’ bacterial respiratory diseases, susceptible drugs, and resisted drugs according to pathogens showed differences between farms. Among the β-lactam-based antibiotics, cephalosporin-based antibiotics showed some efficacy against Streptococcus spp. To review age-based changes in erythrocytometer hemograms in hematological tests of riding horses, red blood cell (RBC) tended to gradually decrease with increasing age this tendency was statistically significant. In addition, leukocytometer hemograms analyzed by age showed that total white blood cell counts tended to decrease with increasing age. These results of drug susceptibility tests and hematological tests, which have not been presented thus far, will be useful as standardized data in future breeding management and disease tests of Jeju riding horses.