Prevalence, Associated Risk Factors and Major Bacterial Pathogens causing Bovine Mastitis on Selected Dairy Farms in and around Harar, Ethiopia

Abstract

Aim
Mastitis, an inflammation of the mammary gland, is a complex and costly disease in dairy herds. The main aim of this study was
to estimate the prevalence of mastitis and associated risk factors for bacterial pathogens in lactating dairy cows.
Methods
A cross-sectional study was carried out. The study was conducted in Harar town and its district from November 2016 to April
2017. A total of 384 (264 crossbreds and 120 Holstein Frisian) milking cows were tested using the California mastitis test (CMT),
direct diagnosis of obverse clinical mastitis, and bacterial culture in Harar City and its district.
Results
The result of the study indicated the prevalence of mastitis at the cow level was 58.60% (225/384), out of which 10.7% (41/384)
and 47.9% (184/384) were clinical and subclinical, respectively. The quarter-level prevalence was 34.1% (513/1536); from this,
the clinical and subclinical forms were 8.7% (131/1536) and 25.4% (382/1536), respectively, while 2% (31/1536) had blind
teats. From 341 culture-positive samples, the following bacteria were isolated: Out of the total, Coagulase-negative Staphylococcus
(CNS) (28.5%) was the most prevalent isolate, followed by Streptococcus species (27.5%), Staphylococcus aureus (21.4%),
Escherichia coli species (14.4%), Micrococcus species (5.3%) and Corynebacterium species (2.9%). Age, parity, breed, production, and
hygiene were significant associated risk factors, whereas management risk factors such as house types, milking systems, farming
systems, and treatment history do not have a significant association with the prevalence of mastitis in the study area at this level
of significance.
Conclusion
Based on the findings of this study, a thorough screening of high-producing and aged cows should be needed; optimum space
should be required for those cows kept in intensive and closed houses to reduce the risk of contagious mastitis; attention should
be paid to the informal use of drugs; and further research should be needed to view other risk factors for mastitis.