Local outbreak of spontaneous pneumothorax secondary to paragonimosis in southwestern Ontario dogs

Three dogs were diagnosed with spontaneous pneumothorax and referred to the Ontario Veterinary College Health Sciences Centre for management. The 3 dogs were diagnosed with secondary spontaneous pneumothorax due to paragonimosis. The diagnosis was made by visualization of adult trematodes during surgical exploration with histopathological confirmation in 1 dog, and detection of trematode eggs via fecal sedimentation in the other 2 dogs. Two of the dogs developed unusual additional lesions, including hemoabdomen, muscle abscess, and abdominal adhesions. These were suspected to be secondary to aberrant fluke larval migration. All 3 dogs lived within a relatively small geographical area of Ontario and were hospitalized between December 2021 and March 2022. Each dog survived to discharge with surgical or medical management of the pneumothorax and treatment with a prolonged course of fenbendazole. Key clinical message: Paragonimosis should be considered as a differential diagnosis for canine spontaneous pneumothorax in areas where Paragonimus kellicotti is, or may be, endemic, or in dogs that have travelled to endemic areas - particularly if the patient has a history of cough or potential exposure to freshwater crayfish. Routine anthelmintic treatment does not prevent infection and standard fecal floatation methods may not detect the eggs. Therefore, diagnostic testing should include a fecal sedimentation test and thoracic radiographs to screen for P. kellicotti.