Piscichuvirus-associated meningoencephalomyelitis in a free-ranging American alligator (Alligator mississippiensis).

The American alligator (Alligator mississippiensis) is a keystone species of the southeastern United States. In December of 2022, a free-ranging American alligator was found stuporous and tetraparetic. On postmortem evaluation, lesions were limited to the central nervous system, consisting of prominent perivascular cuffs of lymphocytes and histiocytes that extended into the surrounding neuroparenchyma along with gliosis. Next-generation sequencing of the affected brain identified the presence of a piscichuvirus closely related to the freshwater turtle neurovirus 1 (FTuNV-1) recently reported in an alligator snapping turtle with similar microscopic lesions. In situ hybridization using zz-probes that recognize FTuNV-1 identified widespread hybridization signal in neurons and glial cells in the alligator's brain and spinal cord. This case represents only the second association of piscichuviruses with vertebrate disease. Moreover, it highlights the potential for disease transmission between different orders (Crocodylia and Testudines) of free-ranging aquatic reptiles that share similar habitats in the United States.