Dg. Rogers et al., LUNG AND NASAL LESIONS CAUSED BY A SWINE CHLAMYDIAL ISOLATE IN GNOTOBIOTIC PIGS, Journal of veterinary diagnostic investigation, 8(1), 1996, pp. 45-55
The objective of this study was to determine whether a chlamydial isol
ate recovered from nasal swabs from swine with pneumonia could cause p
neumonia and rhinitis in gnotobiotic pigs. The identity of the isolate
currently is unknown, but it shares characteristics with Chlamydia tr
achomatis. After propagation in Vero cells and preparation of the inoc
ulum (2.5 x 10(10) inclusion-forming units/ml), chlamydiae were instil
led into nostrils (1.0 ml/nostril) and lungs (2.0 ml intralaryngeally)
of 15 anesthetized 3-day-old gnotobiotic piglets. Five age-matched gn
otobiotic piglets were anesthetized and sham infected with uninfected
cell culture lysates. Two treated piglets were moribund and 2 were sev
erely dyspneic prior to necropsy 7 days postinfection (DPI), whereas r
emaining treated piglets showed mild dyspnea upon exertion throughout
the study. All treated piglets developed diarrhea. All treated piglets
necropsied 7-21 DPI had extensive consolidation in cranial, middle, a
nd accessory lung lobes; a majority of these piglets also had extensiv
e consolidation in the caudal lobes. Treated piglets necropsied 28 and
35 DPI had a lobular pattern of consolidation in all lung lobes. Hist
ologically, lesions in lungs from treated piglets necropsied 7, 14, an
d 21 DPI were characterized by bronchointerstitial pneumonia with foci
of type II pneumocyte hypertrophy and hyperplasia; pneumocytes and br
onchial and bronchiolar epithelial cells were markedly vacuolated. Alv
eolar macrophages, peribronchitis, peribronchiolitis, and perivasculit
is were seen in lungs from treated piglets necropsied 28 and 35 DPI; t
hose necropsied 28 DPI also had foci of lymphohistiocytic and plasmacy
tic infiltrates. Turbinate lesions in all treated piglets were charact
erized by mild multifocal lymphoplasmacytic and occasionally neutrophi
lic rhinitis. Immunohistochemistry detected chlamydial antigen in bron
chial and bronchiolar epithelial cells, pneumocytes, and inflammatory
cells in treated piglets necropsied 7, 14, and 21 DPI. Positive staini
ng was limited to alveolar macrophages in treated piglets necropsied 2
8 and 35 DPI. Chlamydial antigen was detected in turbinate epithelial
cells at all necropsy intervals. Ultrastructurally, chlamydiae were se
en with glycogen particles in vacuoles or free in the cytoplasm of bro
nchial and bronchiolar epithelial cells and pneumocytes. The results i
ndicated that the chlamydial isolate used in this study is a pathogen
in gnotobiotic pigs.