April 2010, tilapia streptococcus disease in Hainan
Province, which was dotted occurred, indicating the
occurrence of streptococcal disease in the extended
season, also means streptococcus may be widespread in
2010.
□ Text / Figure Freshwater Fisheries Research Institute of
Fujian Province, Hai-Ping Fan
1, Streptococcus Overview
Worldwide death of fish caused by streptococcal infection
in the twentieth century has been sporadic seventies and
eighties reported nineties the rise, now has become a major
streptococcal pathogens of fish. Primary infection of
Streptococcus fish head, fish brain damage, then damage
the blood circulation through the liver, kidney, spleen and
other organs caused systemic hemorrhage, is a bacterial
disease, contagious, high mortality, treatment difficulties
and the higher the temperature the more severe disease.
Streptococcus cultured species have a certain selectivity,
occur mainly in salmonids, tilapia, catfish, carp and
freshwater pomfret, and grass carp, carp, silver carp and
bighead carp have not been reported. Streptococcus
infection reported in literature tilapia strains are mainly
dolphins Streptococcus (S.iniae) and Streptococcus
agalactiae (S.agalaciate), the domestic strains of
Streptococcus isolated from Streptococcus mostly dolphins,
Fujian Institute of Freshwater Fisheries S. agalactiae was
first reported outbreak of deaths caused by tilapia.
Robinson and Meyer in 1966, first reported in U.S.
freshwater fish golden bream (Notemigonus crysoleucas)
an isolated group B Streptococcus.
Subsequently, Plumb and Baya isolated from fish such
as multiple strains of non-hemolytic streptococcus
group B, but not sure is right. 1994, Eldar, etc. to be
called Streptococcus difficile. Wilkinson, Elliott, and
Vandamme, etc. to isolation and identification of
streptococci, mostly assigned to group B Streptococcus
agalactiae. 2002, Evans and other re-reported hemolytic
Streptococcus agalactiae is the major pathogen of fish. In
2005, Kawamura and other proposed re-division of S
difficilis attribution, identified as Streptococcus agalactiae
synonyms. 2006, Evans and other marine mammals from
isolated Streptococcus agalactiae. Streptococcus agalactiae
is considered the sole owner of group B Streptococcus-
specific antigen.
Second, an overview of Tilapia Streptococcus
Streptococcus disease occurs mainly in poor water quality,
breeding density of water, low-cost long-term use of low-
quality feed is also contributory factors. In addition, there is
a lot of streptococcal bacteria in water also has a direct link.
Sometimes in the natural incidence of ovarian broodstock
can be detected in the presence of pathogens, so there may
be pathogens in tilapia in the possibility of vertical
transmission. Streptococcal disease of fish disease control
are mainly drugs control, ecological control and immune
control.
Chemical drugs and Chinese herbal medicine the most
direct and simple control yes De Kongzhishouduan,
However prolonged use of chemicals inevitably Shi
resistant pathogens Chan Sheng Xing, Daozhifangzhi
failure, Tong Shi Ye Keneng lead to products of the
drug residue Yinqizhiliang health safety Wen Ti.
Therefore, the ecological control and immune control as an
important means of control. Streptococcus agalactiae is a
major pathogen of fish, but also one of zoonotic pathogens
in aquaculture should place no pathogen carrying seed,
maintain good water quality, full fed high-quality feed, the
tracing of pathogens source of infection, cut off the route of
transmission is the important work of ecological control.
Streptococcus disease in the event, both the brain
infection, brain damage, but also damage the liver,
kidneys and other organs, affect the fish's own immune
function, vaccines and immune activator control the
research and development is caused by Streptococcus
agalactiae non-Luo Fish of the Epidemic mainstream.
3, tilapia streptococcus epidemic Overview
Tilapia streptococcus often long-term high temperature,
oxygen, or breeding density is too large outbreaks such
circumstances, in the spring, summer and autumn, is the
peak was from May to September, popular water
temperature 25-37 ฀, in particular water temperature
higher than 30 ฀, easily lead to disease outbreaks; main
hazards broodstock and 100g or more juvenile and adult
fish. Contagious, the incidence rate is 20-30%, the
incidence of fish mortality rate of 80%, and duration of
long duration, mortality continued to peak 2-3 weeks; In
winter, the mortality rate is relatively low, but longer
duration . China's major farming areas such as tilapia
Hainan, Guangdong, Guangxi, Fujian and other areas in
recent years, outbreaks of different degrees, resulting in a
more serious losses.
IV symptoms and pathological changes
Tilapia streptococcus main symptoms: prevalence disease
fish losing balance, some tumbling in the water, some
sideways movement to do a circle; serious condition, the