Detection of Anguillicoloides crassus (Nematoda) and a survey of endohelminths of American eels in Georgia, USA.

Abstract

The American eel Anguilla rostrata is a catadromous fish with a unique life history; however, parasite surveys of these eels in the southeastern USA are limited. In this study, we surveyed the parasite fauna of 98 American eels collected from the Altamaha and Ocmulgee rivers in Georgia between January 2024 and August 2025. Eels were examined for external and internal parasites. The invasive, pathogenic swim bladder nematode Anguillicoloides crassus was detected in 62 of 98 eels (63.2% prevalence), with all infections occurring in the Altamaha River population. Infected eels harbored up to 21 nematodes, although most infections consisted of fewer than 5 individuals. No clear seasonal trends of infection were observed. The prevalence and mean intensity of A. crassus infections observed in Georgia were higher than those reported for most other regions along the US east coast. This study provides the first published record of A. crassus from Georgia and expands the known parasite diversity of American eels within the state. Our data also demonstrates the presence of 2 trematode genera, 3 cestode genera, 6 nematode genera, 3 acanthocephalan genera, and 1 arthropod genus. Many of these represent the first reports from eels in the state of Georgia.