Streptococcus equi Infection in Foals Associated with Some Clinicopathological Alterations

The study was designed to review the occurrence of Streptococcus equi (S. equi) infection in Egyptian Arabian horses, investigate the virulence gene and phage-related bacterial superantigens (SeeM, seeI, SeeH, and SeeL) of S. equi in the isolates, and evaluate the hematological and serum biochemical characteristics of horses with its infection. A total of 100 horses were examined, with 80 having respiratory tract infections and 20 healthy horses. Samples of nasal swabs, pus, and blood were collected for laboratory diagnosis. Bacterial isolation, identification, and molecular diagnosis of S. equi were performed using a polymerase chain reaction. 34% of samples from diseased horses were detected for S. equi, and the antimicrobial susceptibility pattern of S. equi revealed that Penicillin G was highly effective, followed by Ceftiofur, while ampicillin and tetracycline were less effective. S. equi showed high resistance to Vancomycin and Chloramphenicol. Molecular characterization of S. equi revealed that the 16S rRNA gene, sodA gene, seM gene, SeeM gene, and seeI gene were amplified in all tested isolates. Further analysis showed that three isolates were optimistic for the virulence gene SeeH, while the SeeL gene was found in two isolates. The hematological and biochemical analysis revealed that Arabian horses that were strangled exhibited anemia, leukocytosis, and neutrophilia. Additionally, there was an increase in the levels of total proteins, serum globulins, serum AST, potassium, and phosphorus. Conversely, there was a decrease in the levels of albumin, calcium, and sodium in the affected horses, while creatinine and urea showed no significant changes. Treatment with penicillin resulted in an improvement in all. The study underscores the importance of taking appropriate measures to prevent and control S. equi infection in horses to minimize the potential impact on animal health and economic losses.