Abstract:
Mastitis is a disease of major economic importance in dairy industry worldwide particularly in
Ethiopia. A cross-sectional study was carried out from August 2021 to March 2022 to determine
the prevalence and associated risk factors of bovine mastitis and antimicrobial sensitivity test of
S. aureus isolates in Babile district, eastern Ethiopia. A total of 384 lactating cows managed
under extensive production systems were selected from three selected kebeles of Babile district.
California mastitis test (CMT) was used for screening subclinical mastitis. Likewise, physical
examination was also conducted to detect clinical mastitis. Out of the total animals examined,
50.5% (194/384) had mastitis, where 5.5% (21/384) and 45% (173/384) were clinical and
subclinical mastitis respectively. The quarter-level prevalence was 19.01% (292/1536), from
which the clinical and subclinical form was 2% (32/1536) and 11.97% (184/1536) respectively,
whereas 2.7% (42/1536) of the quarters were blind. Milk samples from positive quarters were
cultured to isolate S. aureus using standard bacteriological test; accordingly, 30.9% of sample
showed growth of S. aureus. Among the risk factors analyzed using a univariable logistc
regression analysis, except lactation stage, all factors such as kebeles, age, parity, body
condition, udder size, milk yield, tick infestation and teats injury were found to be statistically
significant with the occurrence of mastitis (p < 0.05). However, using multivariable logestic
regression analysis udder size, tick infestation and teat injury were significantly associated the
occurrence of bovine mastitis in the study area while the other remaining factors were not
significant. Antimicrobial sensitivity test results of the 35 S. aureus isolates showed that, 100%
susceptible to chloramphenicol and gentamycin. In contrast, the highest (94.2%) resistance was
observed for penicillin G followed by amoxicillin (28.57%) and Erythromycin (20%). The study
confirmed S. aureus was an important cause of bovine mastitis particularly related to potential
risk factors and significant number of S. aureus isolates showed resistance against some
chemical drugs in the study area. Hence, it warrants serious attention for the control of mastitis
considering the risk factors and alternative treatment options
