Bovine Mastitis: Staphylococcus aureus isolation and identification from Small holder Dairy Farms located in and around Hawassa town, Southern Ethiopia

Abstract

Mastitis is a widely distributed disease of dairy cattle in most countries, including Ethiopia. The most commonly recovered bacterial pathogen during mastitis is Staphylococcus aureus in dairy cows worldwide. With this, a cross-sectional study was conducted from March 2021 to August 2021 on dairy farms in and around Hawassa town to isolate and identify Staphylococcus aureus from bovine mastitis milk and to determine risk factors associated with the occurrence of mastitis. A total of 250 lactating cows were randomly selected for clinical and subclinical mastitis from 29 smallholder dairy farms. Clinical signs and the California Mastitis Test (CMT) were used to identify clinical and subclinical mastitis, respectively. Accordingly, a standard bacteriological study targeting Staphylococcus aureus was conducted with all (n=127) milk samples collected from clinical and subclinical mastitis cows. Data generated from these methods were analyzed using STATA Corp. Version 12. Association between the risk factors and mastitis were determined with p<0.05 to be a statistically significant one. During the study period, 50.8% of cows had mastitis, of which 4.8% and 46% showed clinical and subclinical mastitis, respectively. The quarter-level proportion was 27.4%; of which the clinical form was 2.9%, while the subclinical mastitis was 24.5%. Logistic regression analysis showed a significant association among cows of different age groups, lactation stages, and frequency of farm cleaning status per day with the occurrence of mastitis (p < 0.05). Bacterial identification targeting S. aureus was done, and this agent was identified in 60 (47.2%) milk samples. This pathogen was found to be higher (47.8%) in subclinical than in clinical (41.6%) mastitis. In conclusion, this study showed that mastitis was prevalent in dairy cattle of the study area, with a higher case of S. aureus in subclinical mastitis. However, the detection of S. aureus in nearly half of the milk sample collected from mastitic cows indicated the possible presence of other pathogens. Therefore, further study to recover other potential pathogens commonly causing mastitis can be a good approach.