Bovine mastitis-associated bacterial pathogens: a systematic review based on some African dairy systems

Mastitis occurs when microbes invade the teat through the teat canal. Most microbes can cause opportunistic infections of the udder. However, fatal infections are due to various species of Streptococci, Staphylococci, and coliforms. Notable economic effects of bovine mastitis include reduced milk yield, increased treatment costs, and premature culling of affected animals. This systematic review collates published reports of bacterial pathogens isolated from mastitis-positive bovine milk samples in African dairy systems from 2013 to 2023. The search was conducted using Google Scholar, PubMed, Web of Science, and ScienceDirect, and assessed using a modified ROBIS tool. The search terms were: “bovine mastitis”, “bacterial pathogens”, and “African dairy systems”. Findings indicate that Staphylococcus aureus (80%) and Escherichia coli (63%) were among the most frequently reported pathogens. Other frequently reported bacterial species included Streptococcus spp. (37%) and Streptococcus agalactiae (37%). A greater proportion of the studies were based on Ethiopian dairy farming systems. Overall, the results show that mastitis-causing pathogens are common isolates in milk from smallholder African farming systems. Therefore, milk bacterial isolation and testing should be adopted as a standard practice to inform decision-making on mastitis treatment and control programmes.