Vet. Res. 38 (2007) 711-728
DOI: 10.1051/vetres:2007027

A clinically silent respiratory infection with Chlamydophila spp. in calves is associated with airway obstruction and pulmonary inflammation

Julia Jaeger^{a, b}, Elisabeth Liebler-Tenorio^a, Nathalie Kirschvink^c, Konrad Sachse^a and Petra Reinhold<sup>a

a</sup>  Institute of Molecular Pathogenesis in the Friedrich-Loeffler-Institute (Federal Research Institute for Animal Health), Naumburger Str. 96a, 07743 Jena, Germany
^b  Present address: Universität Leipzig, Veterinärmedizinische Fakultät Ambulatorische und Geburtshilfliche Tierklinik, An den Tierkliniken 29, 04103 Leipzig, Germany
^c  Animal Physiology, Department of Veterinary Medicine, Faculty of Sciences, University of Namur, rue de Bruxelles 61, 5000 Namur, Belgium

(Received 12 January 2007; accepted 10 April 2007; published online 10 July 2007)

Abstract - This study was aimed at evaluating functional and inflammatory consequences of persistent chlamydial infections on the respiratory system in clinically inconspicuous calves aged 2-7 months. Thirteen calves persistently infected with Chlamydophila (C.) abortus and/or C. pecorum (Chl+) were compared to 12 calves without chlamydial infections (Chl-). In order to evaluate lung function, 36 non-invasive impulse oscillometry tests were performed per animal within 6 months. The group of chronically infected animals was distinguished by significantly higher peripheral airway resistance (indicating peripheral airway obstruction), significantly higher respiratory rates, and significantly higher minute volumes of ventilation. At the age of seven months, all calves were necropsied, broncho-alveolar lavage fluid (BALF) was obtained ex vivo, and lungs were examined histologically. Significantly higher concentrations of total protein and 8-iso-prostane (8-IP), as well as higher activities of matrix metalloprotease 2 were measured in BALF samples of Chl+ calves. Histologically, markedly activated bronchus-associated lymphoid tissue (BALT) causing partial obstruction of bronchiolar lumina was found in the apical pulmonary lobes of Chl+ calves. Chlamydial DNA was detected in the lung tissue of 7 out of 13 Chl+ calves by real-time PCR. In conclusion, respiratory chlamydial infection appeared to be associated with chronic inflammation of the lungs and airways. Despite the lack of clinical symptoms, pulmonary dysfunctions persisted in calves until the age of seven months. Data obtained in this study provide new insight illustrating the impact of nearly ubiquitous subclinical infections on the respiratory system.

Key words: Chlamydia / Chlamydophila infection / airway obstruction / pulmonary inflammation / calves

Corresponding author: petra.reinhold@fli.bund.de

© INRA, EDP Sciences 2007