[1][4] It was discovered during a study originally aimed at investigating viruses of marine mammals, and was isolated from the bodies of seahorses collected from waters near Miami, Florida.
[1] The name Philasterides dicentrarchi was originally applied to a similar ciliate identified as an infectious parasite in Mediterranean sea bass,[5] but is now recognized as a junior synonym of M.
[7][8] The original 1964 description emphasized the significance of the morphology of the buccal apparatus and specialized oral cilia in differentiating among related ciliates.
[2] In one comparative study, M. avidus infections spread further within host fish and had a significantly higher mortality rate than did similar scuticociliates.
[2] The species is believed to be responsible for a widely reported 2017 scuticociliatosis outbreak on the coast of Northern California, which saw thousands of dead fish and leopard sharks found in the San Francisco Bay.
[2] Protease enzymes are commonly expressed by infectious parasites that damage host tissue, and are believed to play a role in M. avidus infections.