The study was carried out to find the prevalence of Streptococcus equi serovar equi (S. equi) in nasal discharges and pus from sub-mandibular lymph nodes in horses at Lahore and Sargodha districts of Punjab province. A total of 194 nasal swabs and 56 pus samples were collected and examined from horses clinically diagnosed for strangles; 113 (45.2%) were found positive for S. equi. A higher prevalence (87%) of S. equi was recorded in horses with less than two years of age. The haemato-biochemical parameters were also measured at 1st, 2nd, 3rd and 4th week following the onset of infection. Total WBCs, mean segmented neutrophils count (MSNC) and monocytes were significantly increased (P<0.05) while the concentration of lymphocytes was significantly decreased (P<0.05) in infected horses whereas the concentration of total serum protein, serum globulin and fibrinogen was significantly increased (P<0.05), while the concentration of serum albumin was significantly decreased (P<0.05). It is concluded that horses ≤ 2years of age are highly susceptible than adult horses while increased total serum proteins, serum globulin and fibrinogen along with decreased serumalbumin were important indicators of infection by S. equi in horses