To scan or not to scan? Efficacy of transthoracic ultrasonography for ovine pulmonary adenocarcinoma screening in a large commercial UK sheep flock.

BACKGROUND: Transthoracic ultrasonography (TTUS) is currently the only widely used method to diagnose preclinical or subclinical ovine pulmonary adenocarcinoma (OPA) in the live sheep. However, little is known about the test characteristics of TTUS. METHODS: One thousand and seventy-four breeding ewes in a flock with evidence of low OPA prevalence underwent TTUS by an experienced operator. Fifty-one sheep were diagnosed with OPA and underwent gross postmortem examination (PME). RESULTS: Lesions consistent with OPA were found in only 24% (12/51) of the culled ewes. Thirty-five percent (18/51) of culled ewes had gross lesions consistent with other pulmonary disease and 41% (21/51) had no detectable gross lesions on PME. Histopathology and immunohistochemistry confirmed OPA in only the 12 animals identified with OPA lesions from PME. CONCLUSION: Great caution should be exercised when deciding if TTUS is an appropriate screening test in groups of sheep where OPA prevalence may be anticipated to be low. TTUS is a subjective test and thus individual operator ability will influence the sensitivity and specificity of TTUS for OPA diagnosis while the underlying prevalence influences the eventual positive predictive value.

Finding new ways to prevent disease in food-producing animals.

Increasing concern about antimicrobial resistance and moves to restrict the use of antibiotics in food-producing animals mean that farmers will need new ways of preventing and controlling disease in their animals. With its focus on addressing the needs of the farming industry, the Moredun Research Institute sees this as an opportunity to be at the forefront of developing new solutions. Kristy Ebanks reports from an event organised to showcase some of the institute's latest research.

Ovine pulmonary adenocarcinoma as an animal model of progressive lung cancer and the impact of nutritional selenium supply.

Jaagsiekte sheep retrovirus (JSRV) is known to induce ovine pulmonary adenocarcinoma (OPA). Several studies have suggested an influence of selenium (Se) status on cancer progression. Thus, combining OPA with a defined Se supply might serve as a suitable animal model to study the impact of Se on lung cancer progression. 16 naturally JSRV-infected sheep were divided into 2 treatment groups receiving (a) <0.05 and (b) 0.2 mg Se/kg dry matter in diet, respectively. Computed tomography (CT) was performed repeatedly and evaluated using a CT-OPA-score system. Liver biopsies were taken three-monthly, blood samples were collected biweekly to study treatment effects on Se concentrations and glutathione peroxidase (GPx) activity. Cell pellets from bronchoalveolar lavage fluid (BALF) were tested for JSRV by PCR to approve the infection. To date, four animals of the ongoing study have been euthanised. Autopsy and histopathology were performed and correlated to CT analysis. JSRV was detected in BALF cell pellets. Progression of lung tumours was monitored successfully by repeated CT examinations, enabling the detection of even small nodules or increased lung density. Histopathology revealed bronchioloalveolar adenocarcinoma in lung areas suspicious to be OPA from CT evaluation. Score-based analysis of CT images for quantifying tumour progression proved as a valuable tool. Se concentration and GPx activity increased in liver and serum of group b and verified the efficiency of different feeding regime. In conclusion, OPA along with CT, autopsy/histopathology, trace element and enzyme activity analysis provide a suitable large animal model to examine the impact of Se supply on lung tumourigenesis.