Document Type : Original Article
Department of Animal Sciences
Department of Clinical Studies, Faculty of Veterinary Medicine, University of Nairobi, Kenya
Department of Animal Sciences, JKUAT
Department of Animal sciences
Department of Biochemistry, JKUAT
Introduction: Worldwide, there is a paucity of literature on subclinical mastitis, and antimicrobial resistance patterns of bacteria isolated from dairy animals kept in peri-urban areas. This study aimed at determining the prevalence of sub-clinical mastitis (SCM) and the sensitivity of the isolated bacteria to selected antibiotics in dairy cows kept by small-scale farmers in Kajiado North Sub-County, Kenya. Simultaneously, a questionnaire was administered to determine and assess the risk factors associated with mastitis.
Materials and methods: Milk was obtained from all quarters of 101 lactating dairy cows, sampled from 50 farms, and screened for SCM using California Mastitis Test. The samples were cultured and bacteria identified using standard bacteriological methods. Antibacterial sensitivity of Staphylococcus spp. and Escherichia coli isolates were tested using the Kirby-Bauer disk diffusion method, against commonly used antibiotics.
Results: The prevalence of SCM at cow and udder quarter levels were 51.2% and 47.5%, respectively. The prevalence of the bacteria was Staphylococcus spp. (51.4%), Klebsiella spp. (40.5%), Pseudomonas spp. (34.6%) and E. coli (11.8%). The risk factors significantly associated with SCM were breed, parity, lactation stage, and milking hygiene. The highest prevalence of SCM was found in cows in late-stage lactation (78%) with the lowest in those in early-stage lactation (37.5%). A higher prevalence of SCM was found in cows housed in farm structures having poor hygiene (95%). The highest prevalence of SCM was in Friesian breeds (67.3%) and the least affected were the indigenous cows (27.3%). Cows in the fourth and higher parities were the most (64.7%) affected by SCM. Most of the Staphylococcus spp. isolates were found to exhibit resistance to oxytetracycline (73%) but had high sensitivity to gentamycin (69%). All E. coli isolates showed resistance to oxytetracycline while a 75% were sensitive to Chloramphenicol. In conclusion, the study showed that a large proportion of cows were affected by SCM, with the main causative agent being Staphylococcus spp. Conclusion: The study shows that antibiotic resistance was alarmingly high in the study animals. The predisposing factors should be further investigated with a view of developing necessary interventions.