This article is authorized to be transferred from Tongwei Agriculture and Animal Husbandry Information
Text/ Wuxi Tongwei Biotechnology Co., Ltd. Fan Xiaomin Xie Li
Tongwei Animal Health Research Institute Yangtao
Since March, there have been outbreaks of grass carp in Wuxi, Changshu, Zhangjiagang, Kunshan and other places, with 200,000 kilograms of dead fish in farmers, and the incidence of grass carp in Wuxi Changshu area is 70%, and the mortality rate is 50%. During the onset of the disease, farmers have been based on years of breeding experience, in accordance with the direction of water mold disease, parasitic disease and bacterial diseases for treatment, the use of thiosefloxacin, iodine preparations, salicylic acid, glutaraldehyde, copper sulfate and other preparations, fungicides, insecticides, water transfer drugs and even a variety of algae cultivation methods in turn, but still did not see the effect, and even the more drugs are used, the more dead fish. (Click here to review: the epidemic is urgent!) Rare for more than 20 years! Jiangsu, two lakes, Sichuan and many places grass carp large-scale outbreak of "strange diseases", tragic! 200,000 pounds of dead fish have been killed)
At the end of March, Professor Wang Kaiyu, a domestic fish disease expert and doctoral supervisor of Sichuan Agricultural University, visited eight households around Wuxi where the disease of grass carp was more serious. After on-site dissection, drug susceptibility experiments, and testing of water quality indicators, the disease of grass carp in Wuxi area was basically confirmed as grass carp old three diseases and grass carp furuncle disease. Treatment options are provided based on clinical diagnosis combined with experimental results. (Click here to review: The epidemic is on |.) The "strange disease" was attacked fiercely, and a large number of grass carp, bighead carp ponds and box breeding in many parts of the country died violently! The nursing home's eagerly awaited treatment plan is coming)
<b>Chongming Island grass carp continue to develop disease</b>
<b>Similar cases can be found</b>
At the beginning of April, grass carp in the Chongming Island area also continued to develop diseases, with an incidence rate of more than 50% and a mortality rate of 30%. The author visited and investigated eleven farmers with serious fish losses, learned about the incidence of disease, tracked changes in water temperature, tested water quality indicators, dissected, sampled and inoculated pathogenic bacteria on the spot for diseased fish, and brought them back to the laboratory for further testing. Grass carp disease in Chongming Island was basically diagnosed as grass carp old three diseases and grass carp furuncle disease.
<b>1. On-site dissection</b>
<b>Figure 1: Anatomy of Wuxi diseased fish in March</b>
<b>*Sick fish have different degrees of furuncle rupture, gills, spleen enlargement, enteritis and other symptoms</b>
<b>Figure 2: Anatomy of a diseased fish on Chongming Island in April</b>
<b>*Sick fish have different degrees of furuncle rupture, enteritis, gills, liver and spleen enlargement and other symptoms</b>
<b>2. Water quality testing</b>
<b>Table 1, physical and chemical indicators of water quality in some pathogenic ponds</b>
<b>3. Laboratory bacterial identification and susceptibility test</b>
<b>Table 2, laboratory bacterial isolation results</b>
<b>Table 3. Partial results of susceptibility tests</b>
<b>Figure 3, Bacterial isolation results</b>
<b>*Kidney isolated strain (bottom left) and surface ulcer isolate strain (bottom right).</b>
<b>Figure 4, In vitro drug susceptibility screening results for diseased grass carp isolated from diseased strains</b>
*The above work is completed in the National and Local Joint Engineering Laboratory for aquaculture animal disease prevention and control
<b>Treatment options</b>
<b>1. Internal use</b>
According to the results of the susceptibility test, the specific antibiotics used by each farmer are different. For example, Boss Hong uses doxycycline + florfenicol + vitamin C for 5-7 days.
<b>2. Change the water for disinfection</b>
Povidone iodine or benzalkonium bromide glutaraldehyde mixture. Sprinkle once every other morning for 2 consecutive sessions.
<b>3. Handling of dead fish</b>
Dead fish must be covered with quicklime before being buried.
<b>4. Fertilizer water</b>
Algal polypeptide + black gold peptide.
<b>Treatment options are beginning to bear fruit</b>
<b>Control the amount of dead fish on a large area</b>
<b>1. Therapeutic effect of farmers in Wuxi, Changshu and Zhangjiagang areas in March</b>
Of the 8 farmers visited, 6 adopted the author's treatment plan. Two households did not adopt the plan and used methods such as sprinkling quicklime in ponds for treatment. The results of the follow-up visit to 8 farmers after 10 days of treatment are shown in the figure below.
<b>Figure 5, Statistics on the treatment effect of farmers in Wuxi, Changshu and Zhangjiagang areas</b>
<b>Figure 6, Treatment effect of farmers using treatment regimens in March</b>
<b>* Boss Zhou planted 30,000 kilograms of grass carp, and had accumulated 20,000 kilograms of death before the treatment of the plan, and the fish did not eat during treatment. </b>
<b>* Although the number of grass carp deaths of Boss Weng has decreased, it is estimated that there are not many fish in the pond. </b>
<b>Figure 7, Treatment effect of farmers who did not adopt a treatment regimen in March</b>
<b>* Boss Shen did not adopt the treatment plan, using quicklime sprinkling, the weight of death per day increased to 500 pounds, and the cumulative death rate was 3,000 pounds before. Fish do not eat ingredients during treatment. </b>
<b>2. April Chongming Island treatment effect</b>
All of the 7 farmers visited adopted the author's treatment plan. The results of the return visit to the farmer after 7 days of treatment are shown in the figure below. In addition, 4 surrounding farmers also used the same scheme to achieve results, and the number of deaths was greatly controlled.
<b>Figure 8, statistics on the treatment effect of farmers in Chongming Island</b> area
<b>Video: A farmer on Chongming Island has greatly controlled the number of dead fish after adopting a treatment plan</b>
<b>Figure 9.Therapeutic effect of Chongming Island area in April</b>
<b>* Boss Li has accumulated 30,000 pounds of death before adopting the treatment plan. Fish are treated in low feed intake, and although there is a decrease in the number of deaths, it is classified as ineffective. </b>
In addition, Wuxi dealer Gong Boss feedback that local farmers have basically controlled the epidemic according to the treatment plan
<b>Grass carp deaths have a commonality</b>
<b>Analysis of the cause needs to be comprehensive</b>
In March and April, the deaths of grass carp in Wuxi, Changshu, Zhangjiagang and Chongming Island all have a common feature: the mortality rate of ponds pulling over the net is higher than that of the pond without the net, and the mortality rate of purchased fish fingerlings is greater than that of the original pond fry. Combined with the above clinical anatomical symptoms, laboratory bacterial isolation, drug susceptibility experiments, and treatment results, the author analyzes the causes of the disease as follows:
1. Fish prices are low, most farmers do not feed in winter, grass carp after the energy consumption of the whole winter, the physique becomes weaker, which is conducive to the invasion of pathogenic bacteria;
2. Fish prices are low, the amount of fish produced by farmers is small, the amount of ponds is large, and the management is difficult;
3. This year's temperature and water temperature are higher than in previous years, suitable for the propagation and growth of pathogenic bacteria, and the water temperature rises and falls sharply (Attached Figure 1), causing stress in the fish;
4. Do not change the water throughout the winter, and the indiscriminate release of drugs after the opening of spring leads to a deterioration of the water environment;
5. The water temperature affects the grass carp to eat, and the amount of food eaten by the fish rises after the water temperature rises, and the treatment effect is obvious.
<b>Figure 1, comparison of winter water temperature in the past two years and recent changes in water temperature</b>
<b>Antibiotics are not a "panacea"</b>
<b>The epidemic prevention situation is still grim</b>
In this round, conditional pathogenic bacteria with Yersinia lucidum were isolated from diseased fish organs or diseases, and some diseased fish were isolated from Vismonas and Aeromonas hydrophila. The bacteria isolated in the susceptibility test are sensitive to a variety of antibiotics commonly used in aquatic products, and antibiotic treatment in clinical practice has also effectively controlled the epidemic, and it is speculated that bacterial infection may be the main cause of death of grass carp in this round.
There is also feedback on the front line of breeding that antibiotic treatment is ineffective, and it is speculated that there are two factors
1. The water temperature is low, and the amount of food collected by grass carp after the onset of the disease is extremely low, resulting in insufficient drug administration.
2. No sensitive antibiotics were selected for treatment. According to the habit of farmers, more antibiotic mixtures such as enrofloxacin are selected, and drug susceptibility experiments and clinical practice have shown that enrofloxacin sensitivity is extremely low.
Through the diagnosis and treatment of this round of grass carp disease, there are two suggestions for the reference of the majority of farmers
1. Fish should pay attention to prevention, and adopt the policy of prevention as the mainstay and treatment as the supplement. After the onset of fish disease, the treatment is difficult and the loss is serious;
2. In the process of fish disease treatment, do not indiscriminately feed antibiotics, and take a reasonable and effective treatment plan according to the results of the drug susceptibility experiment. (<b>This article is transferred from [</b><b>Tongwei Agriculture and Animal Husbandry Information</b><b>].) If you have copyright questions, please contact</b> [email protected]<b>. </b>）