Prevalence and major bacterial causes of bovine mastitis in Asella, South Eastern Ethiopia.

A cross sectional study was conducted in and around Asella town from November 2007 to April 2008 on dairy cows to determine the prevalence of mastitis, impact of risk factors and isolate the dominant mastitis causing bacteria on total of 223 lactating cows, of which 92 were indigenous Arsi, and 131 Holstein Zebu cross by using clinical examination and California mastitis test (CMT). Of these 144 (65.6 %) were positive by clinical examination and CMT for clinical and sub clinical mastitis, with prevalence of 26.5 % and 38 %, respectively. There was a significant difference (P < 0.05) on the prevalence of mastitis between cows kept under different hygiene of milking process. Similarly a significant difference on the prevalence of mastitis between the two breeds (P < 0.05) was also observed. From 144 CMT and clinically positive milk samples analyzed microbiologically, 133 were culturally positive for known mastitis pathogens and while 11 were negative. The dominant bacterial isolates in the study animals were Staphylococcus species (41.4 %), Streptococcus species (24.8 %), and other Gram positive rods and Gram negative enteric bacteria (33.8 %). Good hygiene in milking process, milking clinically infected cows at last, culling chronic mastitis carriers, treating clinically infected cows and dry period therapy could reduce the prevalence of contagious mastitis in the study area.