Impact of Anguillicoloides Crassus on Chesapeake Bay American Eels (Anguilla rostrata)

American eels Anguilla rostrata are infected by an introduced parasitic nematode Anguillicoloides crassus, which can cause extreme necrosis of their swimbladders. Despite prevalences of over 90% and the rapid spread of the parasite throughout most of the US range of the eel, effects of this parasite on the eel population are currently unknown. To determine if infection could be contributing to the depleted status of this data poor species, we collected 3 eel life stages (glass, elver, and yellow) along with common zooplankton species from Virginian estuaries where eels are believed to become infected. The prevalence of A. crassus and swimbladder damage in each eel were quantified. The intermediate hosts of this parasite in the US are also unknown, although zooplankton species have been identified in Europe. To address this, we developed and utilized a qPCR method to quantify the prevalence and intensity of A. crassus in our zooplankton samples. We used a force-of-infection model to infer the population level epidemiological effects of infection on eels. The results have implications on the understanding of the transmission of this parasite, as well as on informing species management through examining population level effects of the parasite.