Diagnostic spectrum
Streptococcus equi can also be detected by culture (service 150 Bacteriology (aerobes)).
In culture, both subspecies (Streptococcus equi equi and Streptococcus equi zooepidemicus) are detected and differentiated by MALDI-TOF.
General information
The globally spread and highly infectious equine disease strangles is caused by an infection with Streptococcus equi subsp. equi and is characterised by purulent lymphadenitis and pharyngitis. It used to be a typical disease in young animals which induces long-lasting immunity. Over the past years, however, an increasing number of affected adult horses has been described, with the disease showing a rather atypical progression (mainly fever, respiratory disorders).
Compared to culture, PCR has the advantage of delivering faster results while at the same time offering a comparably higher sensitivity and specificity. This way, the identification of clinically healthy carriers, which play a major role in pathogen epidemiology, is also more reliable.
As PCR does not differentiate between dead or living organisms, a positive pathogen detection should always be formulated as a suspected diagnosis and be confirmed by culture examination.
Clinically, an infection with Streptococcus equi subsp. equi cannot always be distinguished from an infection with Streptococcus equi subsp. zooepidemicus. Streptococcus equi subsp. zooepidemicus can be found in all domestic animals and in humans. In horses, it is a facultative pathogenic commensal; infections can cause, amongst others, respiratory disorders and purulent bronchopneumonia. As with strangles, especially foals and young horses are affected.