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

parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...

of fish. It was first discovered in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

in association with

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

including topmouth gudgeon, but was found to be the causative agent of a disease in the UK affecting

salmonid Salmonidae (, ) is a family of ray-finned fish, the only extant member of the suborder Salmonoidei, consisting of 11 extant genera and over 200 species collectively known as "salmonids" or "salmonoids". The family includes salmon (both Atlantic a ...

species such as

Atlantic salmon The Atlantic salmon (''Salmo salar'') is a species of ray-finned fish in the family Salmonidae. It is the third largest of the Salmonidae, behind Hucho taimen, Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlan ...

and

brown trout The brown trout (''Salmo trutta'') is a species of salmonid ray-finned fish and the most widely distributed species of the genus ''Salmo'', endemic to most of Europe, West Asia and parts of North Africa, and has been widely introduced globally ...

. It is thought to pose more of a risk in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

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 adversely affects the structure or function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical conditions that are asso ...

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 fish belonging to a variety of genera including '' Abramis'' (e.g., ''A. brama'', the common bream), '' Ballerus'', '' Blicca'', '' Brama'', '' Chilotilapia'', '' Etelis'', '' Lepomis'', '' Gymnocranius'', ...

carp The term carp (: carp) is a generic common name for numerous species of freshwater fish from the family (biology), family Cyprinidae, a very large clade of ray-finned fish mostly native to Eurasia. While carp are prized game fish, quarries and a ...

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

References

Fish diseases Mesomycetozoea Ichthyosporea species {{Holozoa-stub