Clinical and Subclinical Bovine Mastitis: Staphylococcus aureus Isolation and Identification from Dairy Farms Located in and Around Hawassa Town, Southern Ethiopia

Abstract

BACKGROUND: Mastitis is an expensive disease of dairy cattle in most countries, including Ethiopia. The most commonly recovered bacterial pathogen from mastitis milk is _Staphylococcus aureus_ in dairy herds worldwide, with huge economic losses in the dairy industry. OBJECTIVE: To isolate and identify _Staphylococcus aureus_ from bovine mastitis milk. Additionally, risk factors associated with the occurrence of mastitis were determined. METHODS: A cross-sectional study was conducted from March 2021 to August 2021 on dairy farms in and around Hawassa town. A total of 250 lactating cows were examined for clinical and subclinical mastitis from randomly selected dairy farms. Clinical signs and the California Mastitis Test (CMT) were used to identify clinical and subclinical mastitis, respectively. RESULTS: 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 prevalence 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 farm hygienic status with the occurrence of mastitis (p < 0.05). A bacteriological study targeting _S. aureus_ was conducted with all (n=127) milk samples collected from clinical and subclinical mastitis cows. 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. 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 recovery of _S. aureus_ in nearly half of the mastitis milk indicated the possible presence of other pathogens. Therefore, further study to recover other potential pathogens commonly causing mastitis can be a good approach.