Incidence of Listeria monocytogenes and other Listeria spp. in Ewes' Raw Milk.

Ewes' milk samples from 287 farm bulk tanks and 17 transport tankers were analyzed for Listeria over a one-year period. Listeria monocytogenes and Listeria innocua were detected in 2.19% and 2.00% of 1052 farm samples, and in 18.38% and 11.76% of 136 tanker samples, respectively. Incidence of Listeria grayi , Listeria ivanovii , Listeria seeligeri and Listeria welshimeri was under 0.4% in farm samples and under 1% in tanker samples. Most farms (93.38%) produced milk free from L. monocytogenes throughout the one-year sampling period. No seasonal influence on milk contamination by Listeria was found. However, ewes' milk contamination by L. monocytogenes and other Listeria spp. was significantly higher in farms where cows were also reared than in farms where only ewes were present.