Thoracic Radiographic Features of Silicosis in 19 Horses

Abstract

Clinical records and thoracic radiographs of 19 horses with a confirmed pathologic diagnosis of silicosis were reviewed. These horses had histories of varying degrees of chronic weight loss, exercise intolerance, and respiratory distress. At the time of presentation, two horses were asymptomatic. Ten horses were geldings and nine were female. The mean age of the 19 horses was 10.7 +-5.5 years. Fourteen horses were identified as being from the Monterey-Carmel Peninsula of midcoastal California. An abnormal, structured interstitial pulmonary pattern was identified on thoracic radiographs in each horse. The interstitial pulmonary changes were classified as miliary (13 horses), reticulonodular (4), or linear interstitial (Z), and were best visualized dorsally and caudodorsally. In addition to the abnormal interstitial pulmonary pattern, areas of pulmonary consolidation were evident caudodorsally in seven horses. Other thoracic radiographic features included: hilar lymphadenopathy (4 horses), pleural effusion/thickening (4), cranial mediastinal lymphadenopathy (Z), hyperinflation (l), and a discrete pulmonary mass (1). Necropsy findings in eight horses and results of lung biopsies in an additional five horses showed a diffuse, multifocal, granulomatous pneumonia with areas of pulmonary fibrosis. Cellular infiltrates included predominantly macrophages with intracellular and/or extracellular crystalline material, occasional lymphocytes, and giant cells. Similar cellular changes were also identified, during necropsy, in the hilar and tracheobronchial lymph nodes in each of the eight horses, although gross enlargement of the lymph nodes was present in only six horses. The radiographic and pathologic findings of these 19 horses are consistent with chronic or the accelerated forms of silicosis that are recognized in humans. (Journal of Veterinary Internal Medicine 1991; SILICOSIS is a well-established form of human pneumoconiosis caused by inhalation of particulate inorganic dusts, specifically the crystalline forms of silicon dioxide. 1-5 Development of silicosis in humans is dependent on exposure rate, particulate concentration and size, and host immunologic response factor^.^ Silicosis has been shown to be an occupational hazard, most notably occurring in mining, quarrying, stone-cutting, and sand-blasting workers.Thoracic radiographic abnormalities that are associated with human silicosis have been divided into two general types, simple and complicated (conglomerate) silicosi~.~-~ In simple silicosis, diffuse small (< 1 cm), nodular pulmonary opacities and hilar lymphadenopathy are evident. In 30% of the patients, "eggshell" calcificaFrom the

Multinodular pulmonary fibrosis in five horses

“…[4][5][6][7][8][9][10] Various etiologies, including pathogens, 5,9,11 inhaled or ingested toxins, 8,[12][13][14][15][16] and hypersensitivity reactions, 8,17 have been incriminated as potential causes of interstitial pneumonia. However, defining the exact etiologic agent is challenging because of the chronic insidious nature of the disease.…”

“…Reported clinical signs associated with interstitial pneumonia in horses are variable and range from the absence of overt clinical signs to severe respiratory distress. 9,15 Fever, cough, inappetance, weight loss, nasal discharge, exercise intolerance, tachycardia, tachypnea, and dyspnea have been consistently reported in horses with interstitial pneumonia. [7][8][9][10]20 Equine multinodular pulmonary fibrosis is a recently described fibrotic interstitial lung disease of horses that is associated with infection with EHV-5.…”

Exposures and Health Effects from Inorganic Agricultural Dusts

“…Berry and colleagues have described silicosis in 19 horses in California (42). Most of the horses were symptomatic with severe restrictive lung disease.…”

Pulmonary and hepatic eosinophilic granulomas and epistaxis in a horse suggestive of multi‐systemic eosinophilic epitheliotropic disease

“…Interestingly, when questioning the owner further it was revealed that under previous ownership the horse had been maintained in a pasture next to a large stone quarry so inhalation of particulate material similar to what has been described for causing silicosis, a pulmonary disorder caused by inhalation of the crystalline forms of silicon dioxide (Berry et al . ), remained a possibility.…”