In pigs, diseases of the respiratory tract like pleuropneumonia due to Actinobacillus pleuropneumoniae (App) infection have led to high economic losses for decades, report Carsten Brauer of the University of Veterinary Medicine in Hanover, Germany, and co-authors there and at Hannover Medical School. In a paper in BMC Veterinary Research, they state that further research on disease pathogenesis, pathogen–host–interactions and new prophylactic and therapeutic approaches are needed.

In most studies, a large number of experimental animals are required to assess lung alterations at different stages of the disease. In order to reduce the required number of animals but nevertheless gather information on the nature and extent of lung alterations in living pigs, a computed tomographic (CT) scoring system for quantifying gross pathological findings was developed. In this study, five healthy pigs served as control animals while 24 pigs were infected with App, the causative agent of pleuropneumonia in pigs, in an established model for respiratory tract disease.

CT findings during the course of App challenge were verified by radiological imaging, clinical, serological, gross pathology and histological examinations. Findings from clinical examinations and both CT and radiological imaging were recorded on day 7 and day 21 after challenge.

Clinical signs after experimental App challenge were indicative of acute to chronic disease. Lung CT findings of infected pigs comprised ground–glass opacities and consolidation. On days 7 and 21, the clinical scores significantly correlated with the scores of both imaging techniques.

On day 21, significant correlations were found between clinical scores, CT scores and lung lesion scores. In 19 out of 22 challenged pigs, the determined disease grades – not affected, slightly affected, moderately affected, severely affected – from CT and gross pathological examination were correlated. Disease classification by radiography and gross pathology agreed in 11 out of 24 pigs.

Brauer and co–authors concluded that high–resolution, high–contrast CT examination with no overlapping of organs is superior to radiography in the assessment of pneumonic lung lesions after App challenge.

They added that the new CT scoring system allows for quantification of gross pathological lung alterations in living pigs but that computed tomographic findings were not informative about the aetiology of respiratory disease.

Reference

Brauer C., I. Hennig–Pauka, D. Hoeltig, F.F.R. Buettner, M. Beyerbach, H. Gasse, G–F. Gerlach and K–H. Waldmann. 2012. Experimental Actinobacillus pleuropneumoniae challenge in swine: Comparison of computed tomographic and radiographic findings during disease. BMC Veterinary Research, 8:47. doi:10.1186/1746-6148-8-47

Further Reading

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You can view the full report (as a provisional PDF) by clicking here.

Further Reading

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Find out more information on App by clicking here.

May 2012