Abstract:
A cross sectional study was conducted in Jimma dairy herds from June 2011 to December
2012 with the objectives of determining the prevalence and associated risk factors of sub
clinical mastitis as well as isolating, identifying and determining the antibiotic sensitivities
of Coagulase negative staphylococci infections of the mammary glands. Mastitis is a
serious problem which affects the dairy cows all over the world and there are different
microorganisms which are responsible for mastitis infection in dairy farms. California
mastitis test was used to detect the presence of sub clinical mastitis. Identification of
coagulase negative staphylococci species was carried out based on catalase reaction,
Gram staining, reaction on DNAse media and coagulase test. Antimicrobial susceptibility
test was performed using McFarland standards of disk diffusion method on Mueller Hinton
Agar. A total of 264 lactating cows from 48 herds and 1056 quarters were used. The
overall prevalence of bovine mastitis during the study period was 75.75%. Of this
prevalence of sub clinical mastitis was 62.1% and clinical mastitis was 13.6% on quarter
level in Jimma dairy farms. From total of 264 lactating cows, 72.7% of them were positive
to subclinical mastitis at cow level and 95.8% on herd level. The prevalence of coagulase
negative staphylococci was 23.1% , 22.72% and 72.9% on cow, quarter and herd level,
respectively. No previous history of clinical mastitis and frequency of body washing of
dairy cows have a significant association with the prevalence of sub clinical mastitis
(p<0.05). Late stages of lactation have significant association with the prevalence of
coagulase negative staphylococci infections (p<0.05). The prevalence of coagulase
negative staphylococci were relatively higher on cows with teat injury and in primiparous
(p>0.05). Antimicrobial sensitivity tests found that coagulase negative staphylococci is
susceptible to all antimicrobials employed; Streptomycin (91.7%), Ampicillin (91.7%),
Cefuroxime (91.4%), Tylosin (89.9%), Amoxicillin (91.7%), Trimetroprim (100%) and
Tetracycline (80.6%).
