Streptococcus equi equi infection
Streptococcus pneumoniae infection
Streptococcus pseudointermedius infection
Streptococcus pyogenes infection
Streptococcus zooepidemicus infection
Stringhalt
Sub-acute ruminal acidosis ( SARA)
Subchondral lucency (crush fracture) of third carpal bone
Subconjunctival haemorrhage
Stranger-directed fear (Problem behaviour)