Bronchopneumonia by Streptococcus equi subsp. zooepidemicus in a horse with inhalation of pine branch of Araucaria angustifolia

ABSTRACT: Respiratory problems due to tracheobronchial foreign bodies (FBs) are unusual in horses; although equines kept in pastures eventually inhale FBs, as conifer twigs of Araucaria angustifolia. A 1,5-year-old Criolle foal was presented with hemoptysis, dyspnea, restlessness and fever (40.9 ºC rectal temperature). Complete blood count showed intense neutropenia, monocytosis, thrombocytopenia and hypoproteinemia. Treatment was carried out but no clinical improvement was observed. At the post-mortem examination, marked amount of dark red liquid was observed in the thoracic cavity (hemothorax). The lung parenchyma was diffusely consolidated, predominantly in the cranioventral area, associated with mild pleural fibrin deposition. The right primary bronchus was obliterated by a Araucaria angustifolia pine branch measuring 18 cm in length, with adjacent darkened areas (lung consolidation). Microscopically, there was diffuse necrosis with severe hemorrhage in the lungs, associated with marked neutrophilic inflammatory infiltrate, numerous coccoid bacterial aggregates, and fibrinous pleuritis. Additionally, there was diffuse alveolar edema and multifocal thrombosis. Lung fragments were submitted for bacterial culture and mixed bacterial growth was observed with a predominance of Streptococcus equi subsp. zooepidemicus. Inhalation of branches is not commonly reported in horses, but it must be included in the differential diagnoses of pneumonia, and attention should be taken when allowing horses to graze in areas where the plant occurs.