In these countries, S. iniae has been isolated in a variety of species as illustrated in the following table. 

Fish species Country of isolation Asian seabass/Barramundi (Lates calcarifer) Malaysia, Singapore, Taiwan, Indonesia, Thailand  Malaysia Malaysia, China Pomfret (Trachinotus spp.) Malaysia, 

Epidemiology 
The transmission is horizontal with infection coming from direct contact with infected fish, contaminated fish food or a contaminated environment. As Streptococci bacteria can survive for several months in frozen fish, feeding trash fish considerably increases the chances of infection. Transmission from wild fish to cultured fish has also been reported. Both acute and chronic mortality occurs. Acute outbreaks often occur during the warmer months of the year or when fish are subject to increased stress, with cumulative mortality reaching 80% within a 10-day-period. In a marine cage-farming situation, the peak mortality usually starts suddenly from one cage and spreads progressively to the neighbouring cages as illustrated in the following graph. 

After an acute outbreak, a low-level chronic mortality can carry on for weeks or months with a small number of fish dying every day. Any size of fish can be affected by S. iniae. But most outbreaks will take place on fish of at least 10 g. 

Clinical signs and gross pathology 
Usually, fish infected with S. iniae become lethargic and refuse to feed. As these bacteria target the brain and nervous system, erratic swimming, disorientation and swirling behaviour are commonly observed. Very often, fish show unilateral or bilateral exophthalmia with opacification of the cornea. Petechial haemorrhage can be present at the base of the fins, or around the mouth, operculum or anus. Darkening of the skin is another common external sign. Internally, the symptoms are typical of a systemic bacterial infection with presence of ascites, splenomegaly, enlarged kidney, pallor and haemorrhages of the liver. 

Affected black Seabream (Spondyliosoma cantharus wiht opacification of the cornea)

Diagnosis
Clinical signs and impression smear. The presence of typical clinical signs and demonstration of Gram-positive cocci from internal organs by Gram-stained impression smears constitute a presumptive diagnosis. 
Bacteriology. Samples from brain, liver, spleen and kidney tissues plated on standard, nonselective TSA or BHIA media supplemented with salt if appropriate, incubated at 26ºC for 24 to 48 hours show small (0.5-1.0 mm diameter), whitish, translucent, rounded and slightly raised colonies. Streptococci  are Gram-positive, nonacid fast, non-motile, oxydase-positive, catalase negative, cocci. S. iniae are ß-haemolytic. The identification to the species level is done on the basis of biochemical and phenotypical profile.
Histopathology. Invasion of a large number of Gram-positive cocci can be observed in most organs. Proliferative inflammation with infiltration of macrophages engulfing bacteria and multifocal areas of necrosis are particularly notable in the central nervous system, eye, heart, spleen, kidney and ateral muscles. No notable changes are observable in the gills. 

Control 
Considering the acute nature of the development of the disease, most fish will not be treatable through antibiotic treatment. Presently there is no real effective cure. 

Prevention 
Avoidance. Screening and quarantine of incoming fingerlings and avoiding the feeding of trash fish diet are the two major means of avoidance relevant to Asia. 
Good husbandry practices. Reducing overfeeding, overcrowding and unnecessary stress (such as handling or transportation) can reduce the risk of outbreak. The collection and sanitary disposal of moribund or dead fish  should be observed on a daily basis. These measures may prevent outbreaks or at least reduce their severity. 
Vaccination. A safe and effective vaccine against S. iniae outbreak in fish has been developed by Intervet Norbio Singapore and will soon be available in South East Asia as a major means to control this disease.