Tilapia Streptococcus Infection Raged Through Western Guangdong

Aug 30, 2011

Due to the hot weather and heavy rain after typhoon Nock-ten landed on Guangdong in late July, large-area of tilapia in Maoming, Gaozhou and Huazhou died, and farmers suffered heavy losses until mid-Autumn. Streptococcus infection occurred to 80-90% of fish culture zone in Zhanjiang and Maoming.

Liangcong, General Manager of Guangzhou Wulonggang Seafoods Developing Company, had been tramping various stricken area doing lots of study of this infection. According to his summary, there are three kinds of situation of the dead fish which are,

1.      Acute Death

Quantity of dead fish is big. Fish ate a lot the other day but suddenly died the following day without typical symptoms such as bulging eyes, red body and red gills. Instead, serious ascites, liver variation, such black liver, white liver was found in the dead body, as well as colon, intestinal congestion, a severe contraction of the gallbladder. For this type of disease, prescription treatment of last year is of no use.

2.      Subacute Death

Quantity of dead fish is relatively small comparing to acute death fish. Symptoms of suspected Streptococcus were found.

3.      Chronic Death

Several dozens of fish die each day. Water quality is good in these fishing ponds.

For variety symptoms and different mortality of the disease, Dr. Huang from Guangdong Ocean University said, “reasons falls to virulence strength of the strains, individual differences, different culture conditions and drug use,” Dr. Huang and the lab he belongs to, carried out sample testing in Gaozhou, Maoming, Zhanjiang Lianjiang and Wuchuan recently, “Test shows that mostly are streptococcal infection”.

For treatment and control, Dr. Huang said it was very difficult, “we mainly rely on combination of disinfect and internal medicine, but there would be recurrence after a week or so. Thus, after using antibiotics for treatment, fed up of some protective and choleretic drugs and nutrients, including probiotics and lactic acid bacteria are necessary. In addition, adjusting the water to keep balance of algae and bacteria is important too.”

According to Liangcong’s observations, keeping oxygen machine fully open, regular disinfection of water, sufficient supply of glucose, Vc and other nutrients, and adding probiotics, such as Bacillus, EM bacteria to adjust water, will help reduce the chance of fish dying.  “Keeping oxygen machine fully open is very important,” he indicated in particularly, “others are all empty talk if ponds lack dissolved oxygen, and also oxygen machine can mix upper and lower water and avoid water stress caused by temperature difference.”