EARLY DIAGNOSIS OF LENTIVIRUS-INDUCED INFILTRATIVE LUNG-DISEASE IN SHEEP BY HIGH-RESOLUTION COMPUTED-TOMOGRAPHY

The visna-maedi lentivirus can induce an interstitial pneumonitis in s heep, and provides a convenient example to study natural or experiment al lentiviral pathology, We wanted to determine whether high resolutio n computed tomography (HRCT) is able to detect early morphological cha nges following lentiviral infection in the lungs. Spontaneously infect ed adult sheep (n=3) and experimentally infected lambs (n=5) were comp ared to uninfected controls (n=4). The HRCT scans generally showed abn ormal features in infected animals, including: increased parenchymal d ensity; alveolar oedema; thickened interlobular septa; and increased d ensity in peribronchiolar areas. HRCT was more sensitive than chest ra diography for the early diagnosis of interstitial pneumonitis, althoug h one sheep with advanced disease and radiographic and histopathologic al abnormalities had a paradoxically normal scan. One control animal s howed minor abnormalities on scanning, which were probably due to the procedure used for anaesthesia. The HRCT observations were confirmed b y postmortem histological examination of the lungs. In conclusion, hig h resolution computed tomography provides a noninvasive means of follo wing the development of lung pathology in a natural ovine model of len tiviral disease.