Pleural effusion associated with acute and chronic pleuropneumonia and pleuritis secondary to thoracic wounds in horses: 43 cases (1982-1992).

Case records of 43 horses with pleural effusion associated with acute pleuropneumonia, chronic pleuropneumonia, or pleuritis secondary to a penetrating thoracic wound were reviewed to determine the predisposing factors, diagnosis, and treatment of this condition. Acute pleuropneumonia was diagnosed in 36 horses, the majority of which were Thoroughbreds (89%). Of 22 (61%) horses that were in race training at the onset of illness, 11 (31%) had been recently transported a long distance and 4 (11%) had evidence of exercise-induced pulmonary hemorrhage. Physical examination findings and hematologic data were nonspecific. The most consistent abnormality was hyperfibrino-genemia. Affected horses were treated with antibiotics, thoracic drainage, nonsteroidal anti-inflammatory drugs, and supportive care. Twenty-two (61%) horses were discharged from the hospital, with the mean duration of hospitalization for those discharged being 23 days. Nine (25%) horses were euthanatized and 5 (14%) died. Bacterial culturing of thoracic fluid resulted in growth in 30 of the 36 (83%) horses. The finding of anaerobic bacteria in thoracic fluid was not associated with a lower survival rate (62%) than the overall survival rate (61%). Four horses with chronic pleuropneumonia had a history of lethargy and inappetence for > 2 weeks. Actinobacillus equuli was isolated, either alone or in combination with other bacteria, from thoracic fluid of these 4 horses. Each horse was treated with broad spectrum antibiotics and made a rapid recovery. Three horses with acute pleuritis secondary to penetrating thoracic wounds also had nonspecific clinical signs, apart from the wound and a large volume of pleural effusion. Bacteriologic isolates from these horses differed slightly from those of horses with acute pleuropneumonia.