Molecular investigation and potential risks associated with Streptococcus equi infection in horses with upper respiratory tract infection

Abstract

The aim of the present study was to conduct molecular investigation and potential risks associated with Streptococcus equi infection in horses with upper respiratory tract infection. For this aim, sixty-nine horses were used (50 diseased and 19 apparently healthy). Horses under investigation were subjected to clinical examination and bacteriological investigation of nasal swabs. Polymerase chain reaction (PCR) for confirmatory identification of Streptococcus equi subspecies equi came to match the isolation percentage on its selective medium. For Streptococcus equi subspecies equi, sodA and seeI genes were detected at molecular weights of 235 bp and 520 bp, respectively. There was a significant (P value <0.05) association between breed, use, vaccination, number of affected animals in the premises, over-crowding and climatic conditions and the isolation frequency of Streptococcus equi subspecies Equi infection. The highest percentage of isolation was recorded in Arabian horses (32/53; 60.4%) compared with other breeds (21/53; 39.6%). Horses kept for racing or showing revealed higher isolation percentage (32/53; 60.4%) compared with draft horses that showed isolation percentage of (21/53; 39.6%). Vaccinated horses also showed a higher rate of isolation (29/53; 54.7%), compared with non-vaccinated ones (24/53;45.3%). The results of the present study highlighted the potential risk factors associated with S. equi subspecies equi in horses with upper respiratory tract infection. The present finding may support the authorities to construct strict preventive measures for this infection.