First record of Macracanthorhynchus hirudinaceus (Pallas, 1781) in Didelphis marsupialis (Linnaeus, 1758) from the Brazilian Amazon.

This study presents the first documented occurrence of Macracanthorhynchus hirudinaceus (Pallas, 1781) parasitizing Didelphis marsupialis (Linnaeus, 1758) in Brazil. Specimens were collected in the Soure Marine Extractive Reserve, Marajó Island, Pará state, northern Brazil. In January and February 2025, parasites were recovered from the intestinal region of two hosts. Necropsy revealed acanthocephalans of unusual sizes in the intestinal loops and significant granuloma formation. Additionally, fecal samples were collected from the cecum region. Morphological/morphometric analyses of the helminths and eggs identified in the feces suggest that the parasites are Macracanthorhynchus hirudinaceus. Thus, this study reports the first identification of M. hirudinaceus in D. marsupialis in the Brazilian Amazon, expanding the range of known hosts of this acanthocephalan.