Rapid and Precise Diagnostic Tests for S. equi: An Etiologic Agent of Equine Strangles

Strangles is a highly infectious, worldwide, costly disease, affects the upper respiratory system of equine and is caused by Streptococcus equi. Early diagnosis ought to be performed for infected and carrier horses by rapid and accurate diagnostic methods. Bacteriological culture, Matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI–TOF MS), polymerase chain reaction (PCR) and DNA sequencing of S. equi M-protein (SeM) were the common methods for detection and differentiation of different subtypes of S. equi. In forty percent of suspected strangles cases, bacteriological culture may fail to detect S. equi. Recently, the development of direct sample PCR for estimation of S. equi in samples provides an alternative and potentially more sensitive method for diagnosis of equine strangles. This review article highlights the different methods of diagnosis, the role of chronic carrier in transmission of infection to susceptible animals and the different methods for identification and discrimination of β-haemolytic streptococci in respiratory samples of horses.