The development and pathogenesis of Eustrongylides tubifex (Nematoda: Dioctophymatoidea) in piscivorous birds

Abstract

Experimental infections of laboratory-raised birds supported field data indicating that Common Mergansers (Mergus merganser L.) (prevalence = 20.8%, mean intensity = 3.2) and Red-breasted Mergansers (Mergus senator L.) (prevalence = 4.0%, mean intensity = 1) are important hosts of Eustrongylides tubifex in Ontario. Fourth-stage larvae from naturally infected fish were used to infect birds. In birds, the fourth moult occurred 2 days postinfection and adult worms retained the fourth-stage cuticle. In experimentally infected mergansers, E. tubifex developed in the tunica muscularis of the proventriculus, eliciting raised, oval tumours. Worms matured rapidly, produced eggs 10 to 17 days postinfection, and then degenerated. Tumours resolved rapidly in the proventriculus which returned to its normal condition by approximately 30 days postinfection. Worms were sometimes found in aberrant locations such as the gizzard and liver but this occurred less frequently in Common Mergansers and Red-breasted Mergansers than in other experimentally infected birds (Hooded Mergansers (Mergus cucullatus L.), Great Blue Heron (Ardea herodias L.), Double-crested Cormorants (Phalacrocorax auritus (Lesson), and domestic ducks (Anas platyrhynchos L.).