Molecular Epidemiology of Staphylococcus aureus Isolated from Subclinical Mastitis in Lactating Camels of the Cholistan Desert, Pakistan

Abstract

Subclinical mastitis (SCM) in camels is a significant constraint to milk production and animal health, particularly in arid areas such as the Cholistan Desert, Pakistan. S. aureus is the primary pathogen of SCM due to the diversity of its virulence factors, which complicates the treatment and control of SCM. This study aimed to determine the prevalence of SCM and the molecular epidemiology of S. aureus isolated from SCM in lactating camels in Cholistan. A total of 221 lactating camels were screened for SCM by SFMT. Positive milk samples were microbiologically processed for the isolation and identification of S. aureus. Further, molecular characterization of the isolates was performed to detect the presence of virulence genes. The overall prevalence of SCM was 10.4% (23/221; P<0.05). Among the management systems, stall-fed camels exhibited a higher prevalence (12%; P<0.05) in comparison with the others, in which grazing camels (9%; P<0.05). Age-wise, the prevalence was observed at 13% in camels aged 5–6 years, 11% in those aged 7–8 years, and 14.5% in the 9–10-year age group (P < 0.05). S. aureus was isolated from 24% of SCM-positive milk samples. Molecular analysis showed the presence of major virulence genes: coa (coagulase) at 87.2%, hla (alpha-hemolysin) at 80%, and hlb (beta-hemolysin) at 82.9%, indicating their pathogenicity (P<0.05). This study highlights the prevalence of SCM in lactating Camels of the Cholistan desert, with S. aureus being a major pathogen. The high prevalence of virulence genes underscores the need for selective control measures with a focus on improved milking hygiene and routine screening to control the effects of SCM on camel milk productivity.