Morphological and Molecular Identification of Tritrichomonas mobilensis in Captive Ring-Tailed Lemurs (Lemur catta)

In September 2024, an acute hemorrhagic diarrhea occurred in a colony of captive ring-tailed lemurs (<i>Lemur catta</i>) housed adjacent to an enclosure of squirrel monkeys in Henan Province, China. Three of the ring-tailed lemurs (1-year-old females) died, and necropsy revealed severe cecal hemorrhage. Histopathology demonstrated extensive mucosal necrosis, hemorrhage, and inflammatory cell infiltration in the cecum, with parasite adhesion and invasion into the crypts. Microscopic examination and PCR targeting the ITS1-5.8S-ITS2 region (347 bp) confirmed the presence of <i>T. mobilensis</i> in the deceased lemurs' intestinal contents and in feces from 40.0% (4/10) of the squirrel monkeys. Ultrastructural analysis (SEM/TEM) confirmed that the isolated parasites exhibited the morphology and key features of <i>T. mobilensis</i>, including prominent peripheral hydrogenosomal vesicles. Treatment with metronidazole and supportive care led to the recovery of the surviving lemurs. Post-treatment fecal exams of ring-tailed lemur were negative for <i>T. mobilensis</i>. This report provides the first evidence of <i>T. mobilensis</i> infection in ring-tailed lemurs, indicating cross-species transmission from squirrel monkeys to lemurs, likely facilitated by keeper-mediated mechanical transmission via tools and footwear that were used in both enclosures.