Farm-management and milking practices associated with the presence of Listeria monocytogenes in New York state dairy herds

Knowledge of the relationship between dairy herd management and milking pra ctices with the occurrence of Listeria monocytogenes on dairy farms might a ssist in the development of intervention strategies aimed at eliminating th is organism at the pre-harvest dairy-food-production level. This paper repr esents a first step towards that goal. We carried out a cross-sectional stu dy to identify farm factors that were associated with isolation of L. monoc ytogenes from on-farm in-line milk-filters. Data on these factors were coll ected by personal interview of the farm owners or managers. Logistic regression was used to evaluate the significance of association of each factor while simultaneously controlling for the presence of other fac tors. A systematic approach was developed in which the bivariable associati on of the hypothesized factor's initially was evaluated. All significant fa ctors were then jointly evaluated in a multivariable logistic model. Farms that used a bucket system had significantly higher odds of L. monocyt ogenes as compared to farms that used a round-the-bam pipeline milking syst em (OR = 0.35, P = 0.05) or milking parlor (OR = 0.21, P = 0.01). There was a significant association between pre-milking teat disinfection (OR = 0.26 , P = 0.001) and pre-milking examination of abnormal appearance of milk (OR = 0.4, P = 0.01) against the occurrence of L. monocytogenes. We also found a significant association between the use of E. coli J5 vaccine (OR = 3.3, P = 0.03) and how long dry-cow therapy had been used on farm (OR = 0.34, P = 0.04). (C) 2001 Elsevier Science B.V. All rights reserved.