Subclinical mastitis in water buffalo (Bubalus bubalis) in Bangladesh

Sammanfattning: Globally, subclinical mastitis (SCM) is an important production disease in the dairy industry, for both dairy cattle and buffaloes, and has a great economic impact due to reduced milk yield, milk quality deterioration, treatment costs, culling and risk for antimicrobial resistance (AMR). A cross sectional study was conducted on 17 randomly selected buffalo farms in coastal areas of Bangladesh during Sep and Oct 2019 to investigate SCM in terms of occurrence, predisposing factors, causing pathogens and AMR. There are just a few small previous studies made on the subject in Bangladesh and there is need for better knowledge level of the situation to enable improvements of the sector. A total of 132 lactating buffaloes were included in this study. The number of lactating buffaloes at each farm varied between 1 and 66. Quarter milk samples were collected before the morning milking procedure from each lactating buffalo and were tested with California mastitis test (CMT). Bacterial culturing was performed from all milk samples with CMT ≥2, which was the definition for SCM in this study. The milk samples were cultured on equine- and bovine blood agar, Mannitol-salt-agar (MSA) and MacConkey-agar (MAC) and agents were identified using visual inspection of the colonies as well as by Gram-staining, biochemical testing and matrix-assisted laser desorption/ ionization (MALDI-TOF). All Staphylococcus spp. were tested for production of penicillinase using the clover leaf method. An average of 56% of the buffaloes had SCM, but the occurrence varied substantially between farms (0 - 100%). The most common pathogen was non aureus staphylococci (59%), followed by Micrococcus luteus (9.6%). The average level of penicillinase production within Staphylococcus spp. was 33%. The occurrence of SCM was around the same level compared to results from other recent studies in the region. The causing pathogens were surprising, mainly since S. aureus was more common in other recent similar studies. Since S. aureus is a species commonly recognized to be hard to eliminate from individual dairy herds this gives positive hope for the future.