title: Prions in milk from ewes incubating natural scrapie.
abstract: Since prion infectivity had never been reported in milk, dairy products originating from transmissible spongiform encephalopathy (TSE)-affected ruminant flocks currently enter unrestricted into the animal and human food chain. However, a recently published study brought the first evidence of the presence of prions in mammary secretions from scrapie-affected ewes. Here we report the detection of consistent levels of infectivity in colostrum and milk from sheep incubating natural scrapie, several months prior to clinical onset. Additionally, abnormal PrP was detected, by immunohistochemistry and PET blot, in lacteal ducts and mammary acini. This PrP(Sc) accumulation was detected only in ewes harbouring mammary ectopic lymphoid follicles that developed consequent to Maedi lentivirus infection. However, bioassay revealed that prion infectivity was present in milk and colostrum, not only from ewes with such lympho-proliferative chronic mastitis, but also from those displaying lesion-free mammary glands. In milk and colostrum, infectivity could be recovered in the cellular, cream, and casein-whey fractions. In our samples, using a Tg 338 mouse model, the highest per ml infectious titre measured was found to be equivalent to that contained in 6 microg of a posterior brain stem from a terminally scrapie-affected ewe. These findings indicate that both colostrum and milk from small ruminants incubating TSE could contribute to the animal TSE transmission process, either directly or through the presence of milk-derived material in animal feedstuffs. It also raises some concern with regard to the risk to humans of TSE exposure associated with milk products from ovine and other TSE-susceptible dairy species.
authors.affiliation: UMR INRA ENVT 1225, Interactions Hôte Agent Pathogène, Ecole Nationale Vétérinaire de Toulouse, Toulouse, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Lacroux
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Simon
authors.forename: Sylvie L
authors.initials: SL
authors.lastname: Benestad
authors.forename: Séverine
authors.initials: S
authors.lastname: Maillet
authors.forename: Jacinthe
authors.initials: J
authors.lastname: Mathey
authors.forename: Séverine
authors.initials: S
authors.lastname: Lugan
authors.forename: Fabien
authors.initials: F
authors.lastname: Corbière
authors.forename: Hervé
authors.initials: H
authors.lastname: Cassard
authors.forename: Pierrette
authors.initials: P
authors.lastname: Costes
authors.forename: Dominique
authors.initials: D
authors.lastname: Bergonier
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Weisbecker
authors.forename: Torffin
authors.initials: T
authors.lastname: Moldal
authors.forename: Hugh
authors.initials: H
authors.lastname: Simmons
authors.forename: Frederic
authors.initials: F
authors.lastname: Lantier
authors.forename: Cécile
authors.initials: C
authors.lastname: Feraudet-Tarisse
authors.forename: Nathalie
authors.initials: N
authors.lastname: Morel
authors.forename: François
authors.initials: F
authors.lastname: Schelcher
authors.forename: Jacques
authors.initials: J
authors.lastname: Grassi
authors.forename: Olivier
authors.initials: O
authors.lastname: Andréoletti
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D003126:Colostrum / Q000737:chemistry*; D005260:Female; D006801:Humans; D008321:Mammary Glands, Animal / Q000737:chemistry; D051379:Mice; D008822:Mice, Transgenic; D008892:Milk / Q000737:chemistry*; D018620:PrPSc Proteins / Q000032:analysis* / Q000472:pathogenicity; D011247:Pregnancy; D012608:Scrapie / Q000378:metabolism* / Q000635:transmission*; D034561:Sheep, Domestic; D014018:Tissue Distribution
chemical_list: D018620:PrPSc Proteins