Vol. 10, Special Issue 11 (2021)

Author(s):
Anugraha Mercy Easaw and K Vijayakumar

Abstract:
Subclinical mastitis is one of the alarming conditions affecting the quality of a dairy herd leading to a huge economic loss and cause decrease in the production and value of the milch animal. Staphylococcus aureus causes intramammary infection which leads chronic persistent infections. The organism produces virulence factors which aids in colonization of the mammary gland. The present study was performed for the detection of virulence factors in S. aureus associated with bovine subclinical mastitis. Screening of subclinical mastitis was performed in 100 lactating cows using California Mastitis Test, Electrical Conductivity and Somatic cell count. Using CMT, EC and SCC, 46 per cent, 38 per cent and 48 per cent of animals were found to be positive for subclinical mastitis, respectively. Milk samples from all quarters were subjected to isolation and identification of organisms and 40 per cent animals yielded positive results. From subclinical mastitis cases five isolates of S. aureus were obtained and confirmed by morphological, cultural, and biochemical characterisation. Selected virulence genes including nuc, hla and PVL were detected in the isolated S. aureus organisms. All the isolates were found to be positive for nuc gene, hla gene was detected in 20 per cent of isolates and no isolates possessed PVL gene. Varying frequencies of virulence factors were observed in this study. Understanding of the bovine clonal types prevalent in a herd will aid in the proper prevention and control of the mastitis.