In the laboratory, the sea snail Boonea impressa can be infected and then pass the parasite to an oyster host.

[7] Infested cells are destroyed by the reproducing protist, and many trophozoites are released into the tissues of the host, or into its bloodstream.

The infected oyster becomes stressed, its tissues are pale in color, its gamete production is retarded, its growth slows, it becomes emaciated, its mantle shrivels and pulls away from the shell, and it may develop pockets of pus-like fluid.

[3] Lysis of tissues and blockage of blood vessels causes fatality, but many oysters can persist up to 3 years with active infections.

[7] The protist occurs along the North American coast from New Brunswick to Florida to the Yucatán Peninsula of Mexico.

Significant disease has occurred in Delaware Bay, Long Island Sound, and other parts of the coast of the northeastern United States.

[3] The prevalence of the protist and the disease are influenced by environmental factors such as temperature, salinity, and food availability to the hosts.

[3] At higher temperatures, the chemical defenses of the oyster, particularly its lysozymes, are reduced; infections are more common and more severe in the summer.

Oysters from populations or farms that have experienced disease should not be moved to areas without infestations, because the protist is easily introduced and transmitted.