Fascioloides magna infection in a captive impala (Aepyceros melampus) in Florida, USA

Abstract

Parasitic diseases are associated with diverse clinical signs, and veterinary professionals must be familiar with the presentations of infections in a variety of hosts. As human activity introduces new and exotic host species, expanding our understanding of pathogen effects in new species becomes integral to effective surveillance, diagnosis, and treatment. This article presents the expansion of the known host range of the American liver fluke, Fascioloides magna, with the infection of a farmed impala (Aepyceros melampus) in Marion County, Florida, USA. The gross and histopathological lesions observed are consistent with previous reports of dead-end host infections, particularly black striping across the peritoneum and abdominal viscera, a prominent pseudocyst on the visceral face of the liver, and hepatic fibrosis and biliary hyperplasia associated with tissue taken from that pseudocyst. While no whole or partial fluke was obtained from a field necropsy of the impala, amplification via cPCR and Sanger sequencing of the ITS2 region confirmed the presence of Fascioloides magna DNA in a frozen liver sample. This diagnostic approach was selected following the determination of an absence of fluke eggs in feces, as is characteristic of dead-end and aberrant host infections. While impala likely play little role in determining population-scale epidemiological and ecological dynamics of fluke infections, given their dead-end host status, this report serves as an important reference for managers and veterinary professionals hoping to preserve the health and welfare of exotic bovids that interface with native American cervids, the definitive hosts of Fascioloides magna.

Keywords: Aepyceros melampus; Exotic ungulates; Fascioloides magna; Impala; Liver fluke; Trematode parasite.