Haplosporidium nelsoni

Haplosporidium nelsoni(MSX)
Scientific classification
Domain:	Eukaryota
Kingdom:	Chromalveolata
Superphylum:	Alveolata
Phylum:	Haplosporidia
Species:	H. nelsoni
Binomial name
Haplosporidium nelsoni 1957

Haplosporidium nelsoni is a pathogen of oysters, that originally caused oyster populations to experience high mortality rates in the 1950’s Oyster Diseases of the Chesapeake Bay}}</ref>, and still is quite prevalent today. Haplosporidium nelsoni is also known as MSX (multi-nuclulated unknown). MSX is thought to have been introduced by experimental transfers of the Pacific oyster [Crassostrea gigas], which is resistant to this disease. Mortalities are usually highest in the summer months and also increase in higher salinity waters. MSX reduces the feeding rates of infected oysters leading to a reduced amount of stored carbohydrates. The reduction in stored carbohydrates inhibits normal gametogenesis in the spring with a reduction in fecundity