Psorosperm

Overview
Psorosperm is a name formerly given to a number of parasitic protozoa which produce cystlike or sporelike structures in the tissue of hosts, but now essentially obsolete. Some which affect vertebrate hosts are now identified as coccidia. Others, such as the cause of pébrine in silkworms, are now recognized as microsporidians, and some are regarded as  myxosporidians. The genus Psorospermium itself is a parasite of crayfishes, and belongs to an enigmatic group of unicellular organisms which some biologists think may be related to the common ancestors of animals and fungi.

Origin
The term was introduced in German (as Psorospermien) by J. Müller in 1841. It comes from the Greek ψωρα itch and σπερμα seed.