Emaciation as a Manifestation of Acanthocephaliasis in the Common Eider (Somateria mollissima)

Abstract

An annual die–off of juvenile common eiders (Somateria mollissima) occurs during late winter/early spring in coastal New England. Abnormally high mortality events, including significant numbers of adult birds, have occurred concurrently with die–offs of eiders’ primary food source, blue mussels (Mytilus edulis). In these situations, eiders are forced to switch to less preferred prey such as shore crabs (Carcinus and Hemigrapsus spp.). This species of shore crabs are a known intermediate host for acanthocephalan parasites (thorny–headed worms). Severe emaciation following infection with the acanthocephalan (Polymorphus botulus) is the common finding of an elevated mortality event in spring of 2006. This paper describes clinical presentations of eiders found during annual die–off periods and discusses possible treatment approaches identified in literature.