Isolation of Streptococcus equi subsp. equi from thoroughbred horses in a racehorse-breeding area of Japan.

This research sought to identify the presence of the bacterial infection, known as ‘strangles’, in a specific horse breeding region called Hidaka in Japan. The study, conducted in 1995, found that strangles, caused by Streptococcus equi subsp. equi, has invaded the area and become prevalent among racehorse-breeding farms.

Research Purpose and Method

• The researchers aimed to establish the prevalence of strangles, a disease caused by the bacterial strain Streptococcus equi subsp. equi, in the Hidaka region of Hokkaido – Japan’s primary racehorse breeding area.
• The study began by conducting an epizootiological survey, which is a study of disease occurrence and distribution in animal populations, during the breeding season of 1995.

Findings and Identification Process

• Strains of Streptococcus equi subsp. equi were successfully isolated from two Thoroughbred horses presenting with submandibular lymphadenitis – an inflammation of the lymph nodes below the jaw, a common symptom of strangles.
• The isolates were identified through several measures including serological grouping (a method of identifying microorganisms based on their reactions in certain serological tests), biochemical tests and the analysis of surface proteins via Western immunoblotting. The latter involves a lab technique used to detect specific protein molecules from among a mixture of proteins extracted from cells.

Conclusions and Implications

• The conclusion derived from the research results is that streptococcus equi subsp. equi has indeed invaded the Hidaka district, indicating that strangles has become prevalent in the racehorse breeding farms in the area.
• The findings are significant to the equine industry in Hidaka and potentially across Japan as strangles is a highly infectious disease that can pose serious health risks to horses and economic loss to the industry. This research will assist in planning effective prevention and control strategies to manage the spread of the disease.