Exogenous Sources of Listeria Contamination in Raw Ewe's Milk

Water, feeds, milking equipment, environmental samples and feces from 15 farms producing ewe's milk contaminated by Listeria spp. were examined over a 1-year period, using a two-step enrichment procedure followed by a DNA hybridization test. Listeria spp. were isolated from 19.6% of trough-water samples, 13.1% of feed samples, 36.4% of bedding samples, 80.6% of farmyard-soil samples, and 16.2% of ewe's feces samples. The contamination rates of these samples by L. monocytogenes were 7.8%, 1.2%, 11.4%, 8.3%, and 2.7%, respectively. Tap water and milking equipment were free from Listeria spp. Fecal samples from poultry and birds in the farms exhibited a high incidence of Listeria spp. (72.7% for hens, 28.6% for pigeons and 48.3% for sparrows) and could be responsible for the contamination of trough water and some feeds by these microorganisms.