Prevalence and Risk Factors of Staphylococcal Subclinical Mastitis in Dairy Animals of Chitwan, Nepal

Abstract

Subclinical mastitis (SCM), the asymptomatic inflammation of breast tissue, is the most common form of mastitis in livestock. SCM prevalence and risk factors in dairy animals in Western Chitwan, Bagmati Province, Nepal, were the primary objectives of this study. Out of 243 dairy animals, 104 representing 42.8% were positive for SCM in the California mastitis test (CMT) in the study area. At the quarter level, out of 972 active quarters tested for SCM, 188 (19.3%) were positive to CMT test. The prevalence of Staphylococcal SCM was 39.92% (97/243) and 18.21% (177/972) at animal level and quarter level, respectively. Coagulase Negative Staphylococcus (CNS) (46.33%) was the most prevalent Staphylococcus to cause SCM at quarter level. While at animal level, SCM due to occurrence of both S. aureus and CNS (36.08%) in an individual was more common. High susceptibility towards Amikacin, Ceftriaxone and Gentamicin was seen against both isolates. Low resistance against Amikacin and Ceftriaxone was seen against both isolates. Ciprofloxacin (41.2% vs 27.4%) and Gentamicin (37.8% vs 23.2%) were more resistance towards CNS whereas Enrofloxacin (41.1% vs 25.2%) and Tetracycline (36.8% vs 15.1%) were more resistant towards S. aureus. Older aged, multiparous and late lactating animals had the highest prevalence of staphylococcal SCM i.e., 58.1%, 56% and 52.6%, respectively. The study concludes that there is a high prevalence of Staphylococcal SCM in Western Chitwan, Nepal. CNS is the most common mastitis pathogen. Increased antimicrobial resistance to S. aureus and CNS could be the result of the indiscriminate use of antibiotic drugs without an antibiotic susceptibility test (AST). This study emphasizes the importance of ongoing antibiotic surveillance, excellent farm and animal hygiene, and suitable housing and feeding management.