The Early Bird Catches the Parasite: Potential Invertebrate Pathway for Baylisascaris procyonis to Infect Songbirds.

Baylisascaris procyonis larva migrans is a debilitating and potentially lethal zoonotic, parasitic condition that can infect a large variety of paratenic hosts, including birds and mammals and even humans. The typical pathway to develop baylisascariasis is to ingest B. procyonis eggs from contaminated feces or through contaminated soil where contaminated fecal matter has decayed. I hypothesized that earthworms (Lumbricus terrestris) living in soils contaminated with B. procyonis eggs from decayed feces of its definitive host, raccoons (Procyon lotor), would incidentally ingest B. procyonis eggs, and in turn, if earthworms were consumed by songbirds, songbirds would become infected with B. procyonis larvae, resulting in baylisascariasis. I placed 100 earthworms in B. procyonis-infused soil and determined that 92% of earthworms had a mean and SE of 7.3±0.4 B. procyonis eggs in their alimentary canals. When B. procyonis-infected earthworms were fed to European Starlings (Sturnus vulgaris), 94% (17/18) of starlings displayed signs of ataxia, torticollis, and paralysis, and 11/18 (61%) died within 22 d of first ingestion of B. procyonis-infected earthworms. White blood cell counts of starlings that ingested B. procyonis-infected earthworms increased nearly threefold, percentage of eosinophils increased 25-fold, and percentage of lymphocytes increased and percentage of heterophils decreased from day 0 to day 12 postingestion. Starlings within the control group remained healthy and displayed normal behaviors. This study highlights an overlooked pathway of baylisascariasis in paratenic hosts, which has potential as a mortality factor for many species within terrestrial ecosystems.