Thoracic radiographic features of silicosis in 19 horses.

This research article examines the clinical records and thoracic radiographs of 19 horses diagnosed with silicosis, specifically focusing on the thoracic radiographic features of the disease. The research findings indicate that the affected horses presented with conditions such as chronic weight loss, respiratory distress, and exercise intolerance, and the radiographic features were consistent with those of chronic or accelerated forms of silicosis seen in humans.

Overview of the Research

• The research presents an analysis of 19 horses diagnosed with silicosis, a lung disease caused by the inhalation of silica dust. The clinical records and thoracic radiographs of these horses were closely reviewed. It notes that the horses presented symptoms such as chronic weight loss, exercise intolerance, and respiratory distress, with two horses being asymptomatic at the time of presentation.

Sample Traits and Geographic Factors

• Of the 19 horses, 10 were geldings (castrated male horses) and nine were females, with a mean age of 10.7 years. A significant number of the horses (14) were from the Monterey-Carmel Peninsula of midcoastal California, possibly pointing to geographic or environmental factors influencing the prevalence of the disease.

Analysis of Radiographs

• Radiographic examination revealed an unusual, structured interstitial pulmonary pattern in each horse. The pulmonary changes were classified into miliary, reticulonodular, or linear interstitial, and were most visible dorsally and caudodorsally.
• Additional radiographic findings included pulmonary consolidation, hilar lymphadenopathy, pleural effusion/thickening, cranial mediastinal lymphadenopathy, hyperinflation, and the presence of a discrete pulmonary mass. These findings again aligned closely with features observed in human silicosis.

Post-Mortem Findings

• The article also discusses post-mortem findings from eight horses and results of lung biopsies from five additional horses. These examinations revealed a diffuse, multifocal, granulomatous pneumonia with areas of pulmonary fibrosis, with predominantly macrophage infiltrations containing intracellular and/or extracellular crystalline material, occasional lymphocytes, and giant cells.
• Similar cellular changes were found in the hilar and tracheobronchial lymph nodes in each of the eight horses, although noticeable enlargement of the lymph nodes was seen in only six horses.
• The researchers concluded that the radiographic and pathologic findings of the examined horses were consistent with chronic or accelerated forms of silicosis that are recognized in humans.