【王念澄】評論

本病主要通過初乳傳給新生羔羊，羔羊接觸感染母羊的時間越長，發生率越高；可以通過呼吸道水平傳播，飼養密度過大有助於本病的傳播。MVV也可以通過污染的飲水、飼養和牧草傳播。病毒可經過子宮傳給胎兒，但比較少見。

【只求60考過】評論

【Its science-】評論

Visna virus (also known as visna-maedi virus, maedi-visna virus and ovine lentivirus) from the genus Lentivirus and subfamilyOrthoretrovirinae, is a "prototype" retrovirus that causes encephalitis and chronic pneumonitis in sheep. It is known as visna when found in the brain, and maedi when infecting the lungs. Lifelong, persistent infections in sheep occur in the lungs, lymph nodes, spleen, joints, central nervous system, and mammary glands; The condition is sometimes known as "ovine progressive pneumonia" (OPP), particularly in the United States, or "Montana sheep...