Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii circulation in a dairy farm and sources of milk contamination

Even though dairy cows are known carriers of Arcobacter species, and raw or minimally processed foods are recognized as the main sources of human Arcobacter infection in industrialized countries, data on Arcobacter excretion patterns both in cow and milk are scant. This study aimed to identify potentially pathogenic Arcobacter species in a dairy herd and to investigate the routes of Arcobacter transmission among animals, and the potential sources of cattle infection and milk contamination. This ten-month longitudinal study monitored the same 50 dairy animals, the feed and water they received, and the milk they produced. Quarter milk, animal teats, the milking environment and animals living on the farm (pigeons and cats) were also sampled to evaluate the characteristic patterns in animals, their living environment and in the raw milk they produced. Of the 463 samples collected, 105 (22.6%) were positive for Arcobacter spp. by culture examination. All the matrices except quarter milk and pigeon gut samples were positive with a prevalence varying between 15 and 83% depending on the sample. Only three Arcobacter species, A. cryaerophilus (54.2%), A. butzleri (34.2%) and (32.3%) A. skirrowii, were detected. Pulsed field gel electrophoresis (PFGE) analysis of 370 positive isolates provided strong evidence of Arcobacter circulation in the herd and its recycling: cattle likely acquire the microorganisms by oro-fecal transmission, both by direct contact and/or from the environment. Water appears to be a primary source of animal infection. Raw milk produced by the farm and collected from bulk tank milk was frequently contaminated (80%) by A. butzleri; our PFGE findings excluded the primary contamination of milk, whereas teats and milking machine surfaces could be sources of Arcobacter milk contamination. A strategy of sampling the same 50 dairy animals, feed, water and milk every month for a ten-month period, as well as the samplings of the milking environment were used to evaluate, by pulsed-field gel electroforesis (PFGE), the characteristic patterns in animals, in their living environment and in the raw milk they produced.