Freshwater fish sepsis is an acute infectious disease with the largest number of harmful fish species, the largest age range of harmful fish, the widest epidemic area, the longest epidemic season and the largest loss in the history of fish farming in China. It is said that the economic loss caused by the disease can reach 6 billion yuan per year. After entering the high temperature season, the incidence of this disease is higher and the harm is greater, and the majority of aquaculture producers must pay close attention to and actively prevent and control it.
First, what is sepsis
The so-called sepsis, that is, we often say "bleeding" but not in the ordinary sense of bleeding, congestion, but or can also be popularly understood as "blood bad", it is pathogenic bacteria or condition pathogenic bacteria in different ways to invade the blood circulation system, continue to exist and rapidly multiply, produce a large number of toxins, resulting in multi-organ, multi-tissue damage, and may occur migratory lesions of a disease.
Sepsis, similar to hemorrhagic disease or an upgraded version of hemorrhagic disease, is also known as: bacterial sepsis, bacterial hemorrhagic disease, hemorrhagic ascites disease, ascites disease, freshwater fish outbreak hemorrhage, fish heat distemper and so on.
Bacterial sepsis in freshwater fish was classified as a Class II animal disease in 2008 Ministry of Agriculture Bulletin No. 1125.
Bacterial sepsis can occur throughout the year, mainly prevalent in the water temperature of 25-30 ° C in July to September, is a high temperature fish disease, so it is called fish heat distemper, all kinds of fish can be diseased. The most common fish diseases during the "white dew plague" period are mainly sepsis and hepatobiliary syndrome, followed by parasitic diseases, followed by poor water quality. At the same time, sepsis also contains or is complicated by hepatobiliary syndrome and parasitic diseases (seasonal factors).
(Body surface congestion)
Second, sepsis pathogens: aeromonas and hydrophilic aeromonas
In 2018, the aquatic animal feed innovation team of the Feed Research Institute of the Chinese Academy of Agricultural Sciences and the scientific research units inside and outside the United Nations discovered that the main pathogenic bacteria of aeromonas sepsis in southern China is Aeromonas viridella, and found that aerolysin is the main virulence factor of Aeromonas viridella. Aerosols of Aeromonas vickers can cause damage to the fish intestine, allowing pathogenic bacteria to penetrate the intestinal barrier into the surrounding system, causing infection and sepsis.
The team analyzed the virulence of 17 strains of Aeromonas virienii and 20 strains of Aeromonas hydrophila using a high-throughput model of zebrafish larvae (see figure above), and the results showed that aerolytics can damage the intestinal tissues of the fish, causing Aeromonas viriens to penetrate the intestinal wall and enter the peripheral system. Aeromonas hydrophilus can also produce aerosols, but the virulence and expression level are lower than those of Aeromonas viridella, and only with the help of vitrobacteria aerosol function when mixed with Aeromonas vicarinae, or when the intestinal barrier is not sound under fish stress conditions, can Aeromonas hydrophilus have the ability to cause infection through the intestinal wall.
(Extensive bleeding on the surface of the body)
The causative bacteria of bacterial sepsis have long been considered to be hydrophilic aeromonas, including attenuated vaccines against Aeromonas hydrophila, which have been in use for many years. However, the prevention and control measures against Aeromonas hydrophilus failed to reduce the outbreak and harm of the disease, and the resulting losses still plagued the freshwater aquaculture industry and caused academics to rethink the pathogen of the disease. Therefore, there should be a variety of pathogens of bacterial sepsis, including Yersinia ruckeri and Aeromonas Aeromonas, A. hydrophila, A. sobria, A. caviae guinea pig, etc., and the most reported are Aeromonas.
(Obvious bleeding symptoms)
The suitable growth temperature of Yersinia lucidii is below 20 °C, and the suitable growth temperature of Aeromonas is 20~30 °C. At low water temperatures, it is mostly caused by Yersinia lucidum, and at high water temperatures, it is mostly caused by Aeromonas. Aeromonas infected with aquaculture animals through intestines, wounds, gills, etc. The pathogens of bacterial sepsis are mostly conditional pathogens, and only under certain conditions will they cause fish disease. Sudden changes in water temperature and climate, deterioration of water quality, and low immunity of fish due to parasitic infections are important triggers for fish disease outbreaks.
(Ascites, ascites)
III. Sepsis Pathology (Pathogenesis)
Pathogenic bacteria in the breeding environment can invade the body through broken skin, abnormal mucous membranes (increase or decrease in mucus), and can also be caused by imbalance of microbial flora in the body (such as in the intestine), the proliferation of pathogenic bacteria is triggered, bacteria enter the blood circulation through lymphatic vessels or veins and multiply in them, pathogenic bacteria can multiply in large quantities in the blood circulation system, and transfer to various parts of the body with the blood circulation system, resulting in a systemic inflammatory response in the body, and extensive congestion or bleeding occur in multiple organs and tissues of the body. Sepsis pathogens or infections through the gastrointestinal tract of the fish body invade the blood and transfer to internal organs with blood circulation, causing congestion, bleeding, inflammation, degeneration and necrosis and ulceration of various tissues and organs.
(Forktail catfish: fin congestion)
Sepsis, we ordinary people (not high culture) can be briefly understood as: literally, the fish's blood system is a problem, it refers to the bacteria invading the blood circulation system, growing in the blood and producing toxins and the occurrence of "septic" blood. It is not like the ordinary bleeding disease is due to the damage of the body and bleeding congestion, and the core problem of sepsis is that the blood of the fish is wrong, and the red blood cells in the blood are dissolved, resulting in blood damage, or "scurvy" seems to be easier to understand. Sometimes there is not necessarily a current situation of bleeding or congestion, acute sepsis is due to blood corruption caused by internal organs or body damage, before the external manifestations of exhaustion and death.
(Jejunum, flatulence)
4. Sepsis symptoms
Sepsis is a difficult syndrome that combines symptoms such as rotten gills, bleeding, enteritis, rotten fins (red skin), and mucus abnormalities (either too much mucus or coarse nails). At the beginning of the disease, the diseased fish may have mild hyperemia on the upper and lower jaws, mouth, gill caps, eyes, fin bases and both sides of the fish body, and the amount of food eaten by the diseased fish is reduced, and then the condition is serious, the surface congestion of the sick fish is aggravated, the orbit is hyperemia and the eyeball is protruding. Systemic extensive congestion or bleeding. The anus is red and swollen, and the abdomen is enlarged. Some fish anemia gill filaments become lighter in color. Some diseased fish have scales erected and the gills rot at the ends. Wait a minute.
(flatulence)
Autopsy reveals yellowish or reddish cloudy ascites in the abdominal cavity. The mesentery, peritoneum and intestinal wall are hyperemic translucent, the intestines are inflated or inflated with thin mucus, the intestines are swollen very thickly, and there is no food or a lot of mucus in the intestines. The color of the liver and kidneys is relatively light, showing flower spots, the liver, spleen, and kidneys are enlarged, and the spleen is purple-black; the gallbladder is enlarged, sometimes brownish black. Muscle congestion and bladder congestion may also be seen. Wait a minute.
(Grass carp: liver and intestine abnormalities)
Sometimes sick fish are anorexic, stationary in the water or slow to move in the water or have paroxysmal swimming, scurrying, some rubbing on the edge of the pool, and finally dying of exhaustion. There is also a phenomenon that the fish body can not see obvious symptoms before the dead fish, the occurrence of sudden death, as if the difficult disease is overwhelmed. We analyzed that this should be caused by acute sepsis, perhaps the diseased fish itself is weak, and the number of pathogenic bacteria invading is large and the virulence is strong, which will cause this ultra-acute case.
(Bighead carp: gills and head congestion)
5. Signs of sepsis
In the high temperature season, the general pattern (omen) of the incidence of disease in some fish farming waters is: along the coast of ponds and other waters, many small fish, small shrimp and trout and other small fish will be gathered, and their jaws, gills and abdomen are congested, the anus is red and swollen, swimming slowly, and the back of the fish body becomes dark black. Subsequently, the white carp, silver carp, bream, carp, bighead carp, etc. broke out in turn, and the sick fish lost their balance, rolled up and down, and the various parts of the fish body were bleeding and dying.
In addition, the simultaneous death of two or more farmed fish species in the same fish farming waters can be initially diagnosed as sepsis. When wild trash fish (non-farmed fish) or snails and mussel shells die due to non-drug deaths in farmed water bodies, the initial diagnosis of sepsis can also be made. Asymptomatic death in smallpox on hot days can be initially diagnosed as sepsis. If there is a phenomenon of "dark floating head", slow or unresponsive to the human figure, the performance of muna, day and night floating head, daytime sun exposure does not sink, after excluding the cause of water quality deterioration, can be treated as a prelude (precursor) to suspected sepsis to be analyzed.
(Bream: hyperemia on the surface of the body)
6. Sepsis prevention and control measures
1. Fishing prevention: high temperature sepsis and low temperature water mold outbreak has a certain similarity, like a pair of twin fish disease, low temperature fishing is prone to water mold comprehensive rotten skin disease, high temperature season catching "hot water fish" is easy to cause sepsis, therefore, when catching "hot water fish" in the high temperature season, we must do a good job of anti-stress treatment, try to use the net fishing to avoid flipping the mud (sludge) to cause water mass changes, minimize mechanical damage and water quality deterioration caused by bacterial secondary infection.
(Traverse: intestinal sepsis)
2. Stop feeding and reduce the amount: After the fish suffer from defeat, regardless of whether the liver and gallbladder have lesions, the first measure is to stop feeding and not feed, and then reduce the amount of feeding to reduce the burden of liver decomposition.
3. Special drugs: Now many fish drug manufacturers produce the product name of violent hemologysis, or, violent hemostasis, violent hemorrhage equality and other drugs are special drugs produced specifically for fulminant hemorrhagic diseases, note: There are many names to choose from. Some manufacturers' products are drug ingredients of glutaraldehyde solution, and some manufacturers' products are quaternary ammonium salt or benzalkonium bromide, plus dithiocyanomethane, or add other ingredients. It is effective for bleeding, red skin, printing, vertical scales, furuncles, rotten tails, unexplained deaths, and has a good effect on the treatment of pathogenic bacteria such as Vibrio, Aeromonas hydrophila and mild aeromonas.
4. Hemostatic factors: The drugs that can be used on the market at present are mainly compound preparations, and the available trade name of grass carp or crucian carp with a fierce incidence is "grass carp four disease spirits" (or "grass carp five disease spirits"; the available trade name of the disease of white carp is similar drugs named "flower white carp outbreak stop"; if grass carp, crucian carp, silver carp. If the carp has a disease, it can be used to mix the "four diseases of the grass carp" + "the outbreak of the white carp". Of course, the above drugs are only recommended, similar to the so-called "hemostatic factor" of the fishing drugs, can be referred to the use, the first choice for the treatment of bleeding diseases.
5. Benzalkonium bromide compatibility: use 45% benzalkonium bromide (100 ml per acre) + glutaraldehyde (250 ml use 2-3 acres) compatibility, or 45% benzal ammonium bromide solution (100 ml per acre) + povidone iodine (200 ml use 2-3 acres) to use compatibility, continuous use 2-3 times.
(Intestinal sepsis of the spotted forktail catfish: needle-like hyperemia of the mandibular, hyperemia at the base of the fin)
6. Insecticidal: Fish with parasites generally have bacterial infections secondary to damage to the body surface, and when sepsis breaks out, parasites are more or less present. Basically all pesticides on the market can now be used, but mainly to kill wheel worms, ring worms, anchorhead loach.
(yellowing of bile and bile)
7. Bait for internal use: from the beginning of treatment, take antipyretic and detoxification drugs for 5-7 days, whether there is liver and gallbladder disease should be taken internally, in order to relieve the poisoning and anti-inflammatory effect. Drugs such as trihuangshan, allicin, and florfenicol can be taken internally.
8. Comprehensive treatment:
Sepsis, as a comprehensive fish disease of incurable diseases, must take a comprehensive course of treatment, a course of treatment for 5-7 days, usually using a combination of "external consumption" and "internal administration", the above 1-7 methods can be synthesized, using the following steps to treat:
(1) Cut-off and reduction: Ibid. Item 2.
(2) Internal administration: Ditto item 7 above. From the beginning of the treatment, the internal antipyretic and detoxification drugs are taken, that is to say, when the fish with mild disease can still eat the material, they will start feeding, and if the degree of fish disease is aggravated, they cannot and cannot eat the bait (feed), and they cannot take the bait in the mixture.
(3) Bottom modification: the use of potassium persulfate compound salt or similar bottom modification, both sterilization and bottom change also transfer water, just like cleaning first, cleaning the site garbage, changing the environment where pathogenic microorganisms breed at the bottom of the pond. Aquatic animals are given to improve first, create a good living environment, and lay the foundation for the next step of treatment.
(4) Insecticidal and insecticidal: If it is suspected that a parasite uses insecticides, the worms in the body can be taken internally with albendazole, that is, "intestinal insect clearance", and the surface insects are sprinkled with cypermethrin, avermectin, dimethoate, copper sulfate and other insecticidal drugs.
(5) Bleeding treatment: external drugs for bleeding diseases (the above 3, 4, 5 drugs) and many disinfectants for symptomatic treatment, such as chlorine dioxide, thiocyanomethane, strong chlorine, iodine, etc., continuous use 2-3 times,
(6) Quicklime: No matter what kind of fish disease outbreak, or after the application of various drugs in the treatment process, the ecosystem of fish farming water bodies is generally destroyed, or for a long time, or when the disease is repeated, sprinkling quicklime water can strongly restore the water ecosystem, the final treatment of fish diseases is very effective, 20-50 pounds of quicklime can be used per mu, supplemented by better effect on the use of biological agents.
As mentioned above, a course of about 5-7 days is expected to contain the condition. In addition, the most important point is that the water body must not be hypoxic, even if it is low dissolved oxygen, the more dissolved oxygen, the better, the sick fish and the patient are more afraid of hypoxia, but can not change the water and flush, therefore, the addition of an aerator to the fish disease treatment has an unexpected special auxiliary treatment effect.
The above prevention and control methods are also applicable to the treatment of intractable fish diseases of unknown causes of continuous death.
(Note: Most of the pictures in this article come from the Internet, if there is any dissent, it will be deleted)
See also:
Countermeasures for the prevention and control of fish "albara fever" (attached: incurable fish sepsis)
Fish disease prevention and control: prevention and control of fish bacterial sepsis and fulminant hemorrhagic disease
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