Imaging and score-based quantification of ovine pulmonary adenocarcinoma using computed tomography as an additional tool in advanced clinical diagnosis

Computed tomography (CT) is well established as an up-to-date technique in lung diseases in human medicine and is being progressively used in companion animal medicine as well. So far, visualisation of lung diseases in sheep has been mainly undertaken using X-ray and sonographic techniques. In this study, we examined repeatedly lungs of three sheep from a flock naturally infected with Jaagsiekte sheep retrovirus (JSRV). The infection is known to cause progressive pulmonary adenocarcinoma (OPA). Clinical signs and detection of proviral DNA of JSRV in bronchoalveolar lavage fluid by PCR confirmed the infection of the animals. CT of the lung was carried out under general anaesthesia. Data were compared to thoracic X-rays as well as to a CT scan and X-rays of a non-infected sheep (control). In two animals post-mortem/histopathology was included. A new CT-OPA score system was generated to classify the cancer stage and to quantify cancer progression. In general, CT diagnosis of the lung seemed to be appropriate as an additional diagnostic tool in sheep. Different stages of lung tumours as well as an unattended abscess cavity can clearly be visualised. The presented score-based quantification of oncogenesis provides a scientific tool to characterise adenocarcinoma progression over time in consecutive examinations objectively. Postmortem findings and histopathology showed good correlation with CT data. The obvious advantage of the CT technique in contrast to established X-ray imaging was the early and sensitive detection as well as clear localisation of even slight lung alterations in JSRV infected sheep.