Pulmonary affection is by far the most severe and widespread disease form caused by Small Ruminant Lentiviruses (SRLV) in sheep. The infection implies direct contact between animals and the most important infection route is by the respiratory tract. Disease is insidious and might be seen in one-year-old animals onwards. Non-productive dyspnea is the most common clinical sign and interstitial pneumonia with increased lung size and volume are the pathologic landmarks. Early detection of infected animals is a key step for the diagnosis and it is best achieved by third generation ELISAs that include a multistrain design to detect divergent genotypes. Differential diagnosis must be established with ovine pulmonary adenocarcinoma, the visceral form of ovine caseous lymphadenitis, ovine respiratory complex, gangrenous pneumonia and bacterial and parasitic (Dyctiocaulus filaria, Oestrus ovis) infections. Control is achieved by combining serological and management measures and is based on total or selective culling of infected animals and replacement with uninfected lambs. Serological segregation and replacement with the offspring of seronegative ewes is also a suitable option for control. Selection of resistant sheep might be a future option. Pulmonary affection by SRLV in sheep must be taken into account in the face of a chronic, non-productive dyspnea.

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