[Expression of visna-maedi virus in the mammary secretions of a seropositive ewe during gestation and then an artificial induction of lactation].

Lentiviruses in small ruminants are specially harboured in the mononuclear phagocyte lineage. The virus expression in macrophages is strictly correlated with physiological events of the reproduction life of the host. In a pregnant ewe, Visna-Maedi seropositive, we cultivated infectious cells from mammary secretions, colostrum and milk. In the same animal, a hormonally induced artificial lactation produced the same increase of infectious macrophages in mammary secretions. The virus is more easily obtained by coculture of milk macrophages when the number of macrophages is higher in mammary secretions.