Antimicrobial Resistance Patterns and Bovine Sub-Clinical Mastitis Burden in Low and High Tick Acaricide Resistance Regions of Uganda

Abstract

Mastitis, antimicrobial resistance and acaricide resistance pose significant threats to the development of the dairy industry in sub-Saharan Africa. This study aimed to determine the prevalence of antimicrobial resistance in bacteria isolated from CMT positive cows on farms located in high (HARA) and low (LARA) acaricide resistance challenge regions of Uganda. Among selected herds in both regions, subclinical mastitis (SCM) screening was performed using CMT. CMT positive samples were collected, cultured, bacteria isolated and antibiotic sensitivity tests conducted. Overall, the prevalence of SCM in cows was 71.5% and 27.7% for HARA and LARA respectively. A SCM herd prevalence of 66.3% and 28.2% was recorded for HARA and LARA respectively. Furthermore, 67.5% and 20.8% of the cows in the HARA and LARA groups, respectively, had three out of four udder quarters infected with SCM. Staphylococcus aureus (44.2%) and coagulase-negative Staphylococcus (CNS) (47.6%) were the most prevalent causative agents of SCM isolated from cows from HARA and LARA, respectively. Most isolates from both regions were highly resistant to penicillin (HARA, 84.3%; LARA, 95.6%) and colistin (HARA, 100%; LARA, 97.8%). Tetracycline (77.1%) and oxacillin (76.1%) resistance was high in isolates from HARA and LARA, respectively. Intermediate responses (neither susceptible nor resistant) to antibiotics were more common in isolates from HARA than in those from LARA. With this level of antibiotic resistance, there is a potential risk of failure to control mastitis in dairy cattle using antibiotics, especially in the HARA region, which may possibly jeopardize the growth of the dairy industry in Uganda.