The present study was conducted to investigate the effect of subclinical mastitis on clinic-pathological changes and public health importance in Mastitic cow. A total of 100 individual milk samples from clinically normal udder quarters of 100 dairy cow were collected and examined microbiologically as well as by using California Mastitis Test (CMT) for detection of subclinical mastitis and designing rapid diagnostic tests for other infection. The prevalence of Streptococcus species in the examined samples was (50%), where,17% S. agalctiae, 10 % S. dysgalactiae, 10 %., S. pyogenes, 2%, S.Salivaris, 4%., S. mitis, 3% S. equi, 2% S. mutans and2%, S. angionosus, respectively. Streptococcus dysgalactiae are Gram-positive bacterial pathogens that affect cows in dairy herds and considered as the major causes of economic losses of dairy producers without a control program, somatic cell count revealed highly significant increase in count ≥ 145.000 cell than normal cows ˂ 100.000cells. Two types of blood samples were analyzed for hematology and biochemical analysis (total protein, inorganic phosphorous and calcium. Also LDH (Lactate dehydrogenase enzyme) was detected, where the results indicated that there is highly significant decrease in HB (Hemoglobin) concentration, significant decrease of PCV (packed cell volume) and RBCs (Red blood cells) and significant increase in WBCs (White blood cells) in hematological analysis, while biochemical analysis revealed that, highly significant increase in LDH activity while a notable decrease in total protein and serum calcium were observed. However; Serum phosphorous level did not exhibit obvious changes.