Bovine Mastitis: Prevalence, Risk Factors, and Bacterial Pathogens Isolated in Lactating Cows in Gamo Zone, Southern Ethiopia

PURPOSE: Mastitis is a disease known to cause a great deal of loss of production and has a major economic impact. In the study area, there is little current information on bovine mastitis. Therefore, this study aimed to determine the overall prevalence of bovine mastitis and its associated risk factors and isolate the major pathogenic bacteria. METHODS: A cross-sectional study was conducted from February 2020 to September 2020 in selected dairy farms of Gamo Zone, southern Ethiopia. A total of 422 lactating cows were diagnosed for mastitis using the California mastitis test, clinical examination, and bacteriological methods. RESULTS: The overall prevalence of bovine mastitis determined in the area was 17.1% (72 of 422), of which 1.9% (eight of 422) was clinical and 15.2% (64 of 422) subclinical. Of 1,662 quarters examined, 7.94% (132) were positive. Bacteriological methods were also used to isolate the major pathogenic bacterial species associated with bovine mastitis. From 72 composite milk samples, growth of six different groups of bacteria was recorded in 64 (88.9%) samples. The most predominant bacterial pathogens isolated were Staphylococcus aureus (42.6%), ahead of Streptococcus spp. (26.2%), non-aureus staphylococci (14.8%), and Escherichia coli (11.5%). Salmonella spp. (3.3%) and Klebsiella pneumoniae (1.6%) were the least isolated bacterial pathogens. Among risk factors, breed, parity, udder depth, and tick infestation of the udder showed statistically significant differences (P<0.05) regarding the occurrence of mastitis. CONCLUSION: The current study revealed that mastitis is one of the health problems affecting dairy cows in Gamo. Enhancing the awareness of dairy farmers, regular screening, and improving hygienic conditions are critically important to control and prevent bovine mastitis in the study area.