Hepatitis and splenitis due to systemic tetratrichomoniasis in an American white pelican (Pelecanus erythrorhynchos).

A free-ranging, young adult, female American white pelican (Pelecanus erythrorhynchos), found dead on the grounds of the San Diego Zoo Safari Park in Southern California, had severe multifocal to coalescing necrotizing hepatitis and splenitis on postmortem examination. Histologically, within the large areas of necrosis were myriad pleomorphic, 5-20 µm in diameter, protozoal organisms with 1 to multiple nuclei. Ultrastructurally, the organisms were consistent with a trichomonad flagellate. Polymerase chain reaction and sequencing of the small subunit ribosomal RNA gene identified nucleotide sequences with 99% identity to Tetratrichomonas gallinarum, which is a common inhabitant of the intestinal tract of galliform and anseriform birds that has occasionally been associated with disease, including typhlitis and hepatitis. Damage to the cecal mucosa in the pelican from trematodes and secondary bacterial infection could have allowed invasion and systemic dissemination of the organism. Exposure of the pelican to a variety of native and exotic anseriform and galliform birds at the zoological institution could have led to cross-species infection and severe manifestation of disease in a novel host.