Prevalence of subclinical mastitis, associated risk factors and antimicrobial susceptibility pattern of bacteria isolated from milk of dairy cattle in Kajiado Central sub-county, Kenya.

Abstract

Literature is scarce on the occurrence of bovine mastitis and antimicrobial resistance among dairy animals kept by pastoralists in the Kenya. A cross-sectional study was carried out to investigate the prevalence and risk factors of subclinical mastitis (SCM) and evaluate the antibiotic sensitivity of bacteria isolated from dairy cattle kept by farmers in Kajiado Central sub-county, Kenya. A total of 202 lactating cows from 40 farms were sampled. Milk from the cows was screened for SCM using the California mastitis test, and the bacteria present in the milk samples were determined using standard bacteriological methods. The sensitivity of the isolated coagulase-negative staphylococci (CNS) and Staphylococcus aureus against antibiotics was tested using the Kirby-Bauer disk diffusion method. The prevalence of SCM at quarter- and cow-level was 31.7% and 53%, respectively. The prevalence of SCM was significantly higher (p<0.05) in exotic breeds of cattle and those kept under an extensive system of production. A total of 19 bacterial species were isolated with the majority being CNS (40.1%), S. aureus (15.8%) and Micrococcus spp. (10.4%). S. aureus isolates showed varied resistance to the tested antibiotics with the highest resistance being against ceftazidime (75%), amoxycillin (50%) and streptomycin (46.9%). Several S. aureus isolates were resistant to oxacillin (34.4%) and cefoxitin (12.5%). CNSs were more resistant against ceftazidime (79.1%), amoxycillin (34.6%) and oxacillin (32.1%). Majority (92%-100%) of the Staphylococcus spp. were highly sensitive to ciprofloxacin a fluoroquinolone and augmentin. The high prevalence of SCM and bacteria resistant to antibiotics shows a need for animal health professionals and farmers to develop strategies for the management of mastitis and antibiotic resistance in dairy cows in the study area.