Investigation of asinine pulmonary fibrosis
Non-invasive clinical examination, case/control examination of post mortem material, case review of clinical and pathology records. Whole lungs were collected from 32 aged donkeys (19 APF-like on gross examination and 13 controls) at routine necropsy from 2 UK Donkey Sanctuaries between June 2009 and January 2013. 18 whole inflated ex vivo lungs (11 APF, 7 controls) were imaged with high resolution computed tomography (HRCT) while the remainder were sectioned and photographed digitally. Tissue samples were collected from all lungsinto 10% buffered formalin and processed into paraffin blocks for histopathological evaluation . HRCT images and histology sections were objectively reviewed and categorised as, 'consistent with' or 'inconsistent with' characteristics of pleuroparenchymal fibroelastosis (PPFE). Tissue samples from 8 lungs were also processed for DNA extraction and PCR. Lung sections with granulomatomous inflammation were analysed for fungal hyphae, and Mycobacteria. X-ray diffraction was used to identify both fibrous and non-fibrous dust content.
- To characterise Asinine Pulmonary Fibrosis (APF) on a gross, histopathological and molecular level.
- To perform an epidemiological study, encompassing case histories, environmental management, and potential pathogen and dust exposure.
- Evaluating non-invasive clinical techniques including detailed clinical examination, pulse oximetry and thoracic ultrasound as early diagnostic and disease monitoring tools.
To examine ex vivo lung tissue from a small cohort of aged donkeys with a high prevalence (35%) of fibrosing interstitial lung disease named Asinine Pulmonary Fibrosis.
There was no statistically significant difference between the age of APF and control donkeys. Ten of 19 APF cases were categorised as being consistent with PPFE according to the defined histological and imaging criteria sharing key features with human PPFE. As donkeys are quadruped, the dorsal lung equates to the human upper zone. All 10 PPFE-like lungs had grossly visible visceral pleural fibrosis on the dorsal/costal surface, with no involvement of the parietal pleura. Histologically, all 10 PPFE-like lungs had marked pleural and subpleural fibrosis, predominantly within the upper lung zone, with accompanying intra-alveolar fibrosis and elastosis. It is possible that some of the DPF lungs classified as 'inconsistent' with PPFE may represent an earlier stage of PPFE-like disease. All control cases were classified as inconsistent with PPFE on histology and HRCT. Asinine herpes virus was ubiquitously expressed within both control and APF lung tissue. No other etiologic agents were identified. X-ray diffraction analysis revealed dust contents and small numbers of fibrous and non-fibrous particles.
This study showed that over 50% of donkeys with DPF shared key pathological and imaging characteristics of human PPFE, a rare and usually idiopathic interstitial pneumonia. Further study of APF may yield valuable information to help elucidate the etiopathogenesis of this emerging human disease; in particular how recurrent lower respiratory tract infections may contribute to the pathogenesis of PPFE.