Pulmonary embolization of immature Fascioloides magna causing fatal hemothorax confirmed by molecular technique in a heifer in the United States.

The current report describes the use of a molecular technique to identify immature Fascioloides magna An 18-month-old Brangus heifer was found dead in the field without any prior clinical signs. The cause of death was exsanguination into the thoracic cavity associated with pulmonary embolization and infection by immature Fascioloides magna resulting in 2 large foci of pulmonary necrosis and focal arteriolar and lung rupture. The liver had a few random migratory tracts with typical iron and porphyrin fluke exhaust, but no identified fluke larvae. A single immature fluke was found in the lungs, and species level identification as F. magna was confirmed by DNA sequence analysis of the ribosomal internal transcribed spacer regions (ITS1 region, 5.8S rRNA gene, and ITS2) and of partial 28S rRNA gene sequence. This is one of only a few pulmonary fascioloidiasis cases associated with hemothorax in the veterinary literature.