Bovine Mastitis: Prevalence, Risk Factors and Major Pathogens in Dairy Farms of Holeta Town, Central Ethiopia

A cross sectional study was carried out from November 2008 to April 2009 to estimate prevalence of mastitis and to see associated bacterial pathogens in lactating dairy cows in Holeta town. A total of 107 cross bred milking cows were tested using California Mastitis Test (CMT). Prevalence of mastitis at cow level was 71.0% (76/107), out of which 22.4% (24/107) and 48.6% (52/107) were clinical and subclinical, respectively. The quarter level prevalence was 44.9% (192/428); from this the clinical and subclinical forms were 10.0% (43/428) and 34.8% (149/428), respectively. Out of the 43 quarters with clinical cases, 31 had blind teats while 12 of them revealed active cases of mastitis. Samples from all 12 active clinical cases and 90.0% (134/149) of the CMT positive subclinical quarters were found to be culture positive. From 146 culture positive samples, a total of 153 bacteria were isolated, the most prevalent being S. aureus (47.1%) followed by Coagulase negative Staphylococcus (CNS) (30.1%). Other bacterial isolates included Streptococcus (7.2%), E. coli (4.6%), Micrococcus species (3.3%), Klebsella pneumonae (3.3%), Enterobater aerogen (1.3%), Corynebacterium species (2.0%) and Bacillus (1.3%). Risk factors analysis revealed that prevalence significantly differed with the age (P < 0.05), parity (P < 0.05) and udder hygiene condition (P < 0.03). Thus, prevalence was relatively higher in adult cows (OR = 2.0; 95% CI = 1.15, 3.64), cows with moderate calves (OR = 2.4; 95% CI = 1.6, 3.6), cows with injured teat (OR = 7.7, 95% CI = 0.9, 64.1) and cows with unwashed udder (OR = 2.3, 95% CI = 0.8, 6.4) than those corresponding animals. In conclusion, this study revealed the importance of mastitis and associated bacterial pathogen in the study area.