Accidental Ascaridia nymphii Infection Causing Gastrointestinal Impaction and Hepatic Migration in a Domestic Pigeon in California

Ascaridia nymphii is a roundworm species affecting domestic avian species, initially described in 2015. One pen-reared, 4-year-old, female American Show Racer pigeon (Columba livia f. domestica) was submitted to the California Animal Health and Food Safety Laboratory System (CAHFS) Turlock branch, University of California-Davis, for postmortem examination and diagnostic work-up. Grossly, large numbers of ascarids were in the lumen of the proventriculus, gizzard, and duodenum, and a small number was present in the lumen of the trachea, esophagus, and crop. A focal, coiled adult nematode was embedded in the hepatic parenchyma. Ascarids were tan and measured approximately 3.5-4.5 cm in length. The liver was moderately enlarged, green-tinged, and had small, firm, and off-white scattered nodules. Microscopically, we observed multifocal to coalescing granulomas containing intralesional nematodes delineated by necrotic debris, multinucleated giant cells, eosinophilic and heterophilic inflammation, hemorrhage, and bacterial colonies in the liver. The genotypic characterization of the Ascaridia sp. in our case (GenBank database accession PX488893) shared 100% identity with A. nymphii isolated from the intestinal tract of a cockatiel (Nymphicus hollandicus) from Japan in 2015 (GenBank database accession LC057210.1) based on PCR and sequence analysis of an 815 bp segment of the 18S rRNA gene. This report describes the accidental A. nymphii infection, which caused severe gastrointestinal impaction and hepatic migration in a domestic pigeon.