Evaluation of lung function in pigs either experimentally or naturally infected with Chlamydiaceae

Abstract

This study evaluated the influence of chlamydial infections on lung function in conventionally raised pigs. Eight pigs aged 39-44 days were included in an aerogeneous challenge model (4 were exposed to Chlamydia suis; 4 served as controls). Nineteen pigs aged 5-27 weeks without clinical symptoms (but partly PCR-positive for chlamydial species) were examined over 6 months. For lung function testing, impulse oscillometry was used. In total, all 27 pigs underwent 465 lung function tests. Variables of ventilation (respiratory rate, tidal volume, minute volume), respiratory impedance (expressed as resistance and reactance within the frequency range 3-15 Hz), and model derived resistance of proximal and distal airways were measured. Experimental exposure to C. suis significantly affected lung function. Early distal airway obstruction (3-5 days after infection) was followed by an obstruction of proximal airways (7 days after infection). The breathing pattern was significantly changed (decreased tidal volume; increased respiratory rate). In symptom-free pigs having a naturally acquired presence of different chlamydial species in the respiratory system, no deterioration in lung function could be determined up to the age of 6 months. In conclusion, the consequences of respiratory chlamydial infections appear to vary from clinical inapparence to severe respiratory distress.

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

“…Since the frequency range explored in this study for R (1 to 10 Hz) is sensitive to the peripheral airways, data indicate peripheral airway obstruction in Chl+ calves. These data confirm results obtained in a model of experimental respiratory infections with chlamydiae in pigs, where respiratory chlamydial infection also resulted in significant distal airway obstruction [32], and are in agreement with lung function results obtained in children with bronchial C. pneumoniae infection [39].…”

“…In previous studies on pigs, it became evident that respiratory infections with chlamydiae may vary from severe respiratory distress to mere colonisation without clinical or functional relevance within the respiratory system [32]. Data of the present study represent a third category of subclinical chlamydial infection characterised by persisting pulmonary inflammation and functional disorders of the peripheral respiratory system, but without clinical illness or macroscopic lesions of lung tissue.…”

An experimentally inducedChlamydiasuis infection in pigs results in severe lung function disorders and pulmonary inflammation

“…The continuous increase of FRC as observed between day 5 and day 7 after challenge might be suggestive of trapped air or the development of pulmonary emphysema. Pathogenetically, this phenomenon is supported by earlier observations showing that airflow limitations due to peripheral airway obstructions do affect expiration much more than inspiration in C. suis infected pigs [32]. Whether peripheral airway obstruction and the developing obstructive emphysema as observed one week after infection are reversible, or whether these phenomena represent an early stage that tends towards chronic airway obstruction, deserves further examination in a longer study period.…”

“…Pathogenetically, this was most likely caused by both peripheral airway obstructions (bronchospasms) and reduced pulmonary compliance as observed in an earlier study using the same model [32]. Because the porcine lung lacks collateral airways to ventilate the lung periphery of obstructive regions through pathways for collateral airflow [24], atelectases develop frequently in any obstructive conditions leading to ventilatory asynchronisms, i.e.…”

“…The knowledge about the involvement of Chlamydiaceae in the porcine respiratory disease complex is still limited and reports in the literature are very inconsistent. While lung function was not affected in symptom-free pigs with a naturally acquired presence of chlamydiae in the respiratory system [32], a clear pathogenic potential of Chlamydia species for the porcine respiratory system has been proven experimentally [32,35].…”