Gastric perforation associated with feather ingestion in American shad Alosa sapidissima housed in a multispecies habitat

Pathological conditions associated with feather ingestion have rarely been reported in any species and not previously in fish. From 2013 to 2024, 87 American shad Alosa sapidissima collected from the wild for display purposes were housed in a multispecies habitat within a zoological facility, alongside various fish, invertebrate and bird species from the St. Lawrence Estuary (Quebec, Canada) ecozone. Since 2013, 81 of the 87 shad either died or were euthanized due to health issues, and macroscopic examinations were performed on 36 of these. Bird feathers were present within the gastric lumen in 12 of the 36 fish and were associated with penetrating perforations of the gastric wall with gross evidence of peritonitis in 11 of the 12 cases. Histopathologic examinations were performed in 7 of the affected fish and in 6 revealed the presence of transmural, focally extensive granulomatous infiltration of the gastric wall, centered on foreign bodies morphologically characteristic of feather shafts and barbs. Significant comorbidities included trauma (n = 18) and systemic Ichthyophonus infection associated with granulomatous reaction, which was considered a potential contributory cause of morbidity and mortality in at least 2 fish, including 1 with gastric feather perforation. Incidental encysted anisakid nematodes within the coelomic cavity, intestines and liver were also observed (n = 3). Eight of the affected fish were underconditioned, suggestive of chronic morbidity. This case series indicates that American shad are prone to ingesting bird feathers and highlights a previously unreported health issue associated with keeping this species in mixed exhibits with birds.