''Sphaerothecum destruens'' (the rosette agent) is a

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

of fish. It was first discovered in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

in association with invasive species including topmouth gudgeon, but was found to be the causative agent of a disease in the UK affecting salmonid species such as Atlantic salmon and brown trout. It is thought to pose more of a risk in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...

than in the US, as native species there are more susceptible to the parasite. The disease causes high rates of

morbidity A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

and mortality in a number of different salmonid species and can also infect other UK freshwater fish such as

bream Bream ( ) are species of freshwater and marine fish belonging to a variety of genera including '' Abramis'' (e.g., ''A. brama'', the common bream), '' Acanthopagrus'', ''Argyrops'', '' Blicca'', '' Brama'', '' Chilotilapia'', ''Etelis'', '' L ...

, carp, and roach. The genus ''Sphaerothecum'' is closely related to the genera '' Dermocystidium'' and '' Rhinosporidium''.

References

Fish diseases Mesomycetozoea {{Holozoa-stub