was first identified as the type strain (ATCC 29177) isolated from another dolphin case of "golf ball disease". A biochemical assay measuring arginine dihydrolase activity has been used to distinguish between serotypes (serotype I is positive), though proposed hyperencapsulation of serotype II may represent the most significant functional difference between the two types. Role in disease In fish S. iniae is highly pathogenic in freshwater, marine, and euryhaline fish, and is highly lethal: outbreaks may be associated with 30–50% mortality. It is, therefore, one of the foremost economically important pathogens in intensive aquaculture. In 1997, the global economic impact of S. iniae infection to the aquaculture industry was estimated at US$100 million (one-tenth of which in the United States). As of 2007, infection had been reported in 27 species of fish, including tilapia (genus Oreochromis and Tilapia), rainbow trout (Oncorhynchus mykiss), coho salmon (Oncorhynchus kisutch), Japanese amberjack (Seriola quinqueradiata), red drum (Sciaenops ocellatus), and barramundi (Lates calcarifer, which can be an asymptomatic carrier). Common carp (Cyprinus carpio), channel catfish (Ictalurus punctatus), and goldfish (Carassius auratus) appear to be resistant. Fish raised in intensive aquaculture operations and subject to environmental stressors (i.e. suboptimal temperature, poor water quality, crowding, handling, etc.) are most prone to S. iniae infection. Wild fish populations located both near and far from aquaculture operations have also proven susceptible to S. iniae infection. The site of S. iniae infection and its clinical presentation vary from species to species. In tilapia, S. iniae causes meningoencephalitis, with symptoms including lethargy, dorsal rigidity, and erratic swimming behavior; death follows in a matter of days. In rainbow trout, it is typically associated with septicemia and central nervous system damage. Symptoms are consistent with septicemia, and include lethargy and loss of orientation (as in tilapia), exophthalmia, corneal opacity, and external and internal bleeding. In humans S. iniae can cause opportunistic infections in weakened or immunocompromised humans. It is most commonly associated with bacteremic cellulitis, but has been known to cause endocarditis, meningitis, osteomyelitis, and septic arthritis. The first recognized cases of human infection occurred in Texas in 1991 and in Ottawa in 1994, but the sources of infection were not determined. Human infection with S. iniae was also identified in Toronto between 15 and 20 December 1995, when three Asian patients were admitted to a hospital with cellulitis of the hand after injuring themselves while handling raw fish. All three were found to