In Italy, the normative (Intesa Stato Regioni 25/1/2007) defines the criteria of acceptability of raw milk sold directly to consumers or by automated distributors. It individualizes parameters that must be respected for the most important bacterial agents of food-borne illness, but these do not include emergent pathogens of public health significance such as MAP (Intesa Governo, Regioni e Provincie Autonome di Trento e Bolzano N.5/CSR 2007; Autori Vari 2006).

Many authors have suggested the transmission of various pathogens to the consumer through the consumption of raw milk. Those that play a particularly important role are E. coli O157: H7, thermophilic Campylobacter, Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, and Yersinia enterocolitica. The danger of these pathogens, MAP and other zoonotic agents should lead to an attitude of caution in consuming raw milk.

Our results indicate that almost two-thirds of the sampled farms were infected and that MAP is excreted in the milk. Eight (47.0 %) and twelve (70.6 %) of the 17 dairy sheep farms in the Marche region were positive using BC or ZN staining combined with ELISA, respectively.

The indirect ELISA, performed on milk, was significantly more sensitive when carried out on sheep at the beginning/end of lactation than when performed on animals at the peak of lactation (P < 0.021). This is in agreement with previous works of Williams and Millar (1979) and Nielsen et al. (2002), and could be attributed by the decrease in IgG concentration during peak lactation, causing a dilution effect due to increased milk production. The 21.6 % of raw milk samples that were positive for MAP on ELISA is lower than that reported by Gao et al. (2009), who isolated the organism in 34.6 % (44/133) of samples, but is higher than that obtained in other studies, which recorded rates of isolation of 10.0 % (Ayele et al. 2005), 8.3 % (Streeter et al. 1995) and 11.7 % (Singh et al. 2007).

This study also demonstrated that an immunoenzymatic technique validated from bovine milk can also be applied to the sheep (Ngu Ngwa et al. 2010). In conclusion, the data obtained from this study suggest that ovine paratuberculosis is widespread in the Marche region and that MAP, eliminated through the milk of infected sheep, represents a potential risk of infection to humans via consumption of raw milk and its products. A precautionary approach to legislation should therefore be taken by the competent authority for the protection of public health.