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Fish spore disease (homomyxosporidosis, the same below) is a fish disease with a very high incidence in recent years, which has caused great economic losses to aquaculture production.
There are many species of myxosporidium that harm fish, and the insect body is relatively small, and it produces spores during development. And the myxosporidium parasitism is very extensive, almost every fish can be infected with various organs, and even several species of myxosporidium parasitize in the same organ of the same fish.
Myxosporidium often causes serious epidemics in fish. In North America, Europe and Japan, a salmon trout spin disease is endemic, caused by myxoplasma cerebral worms, which causes salmon trout deaths in large numbers. In various fish farming areas in China, there are also cases of silver carp madness disease (sick fish with thin bodies, upturned tails, up and down, and soon death) similar to salmon trout rotation disease.
Sporangiasis, which has become a major obstacle to fish farming, is quite difficult to treat.
One is that the tough shell of spore formed in the fish body is difficult for the drug to enter. Any topical drug is difficult to be effective at this stage, especially at this stage, it is often the more the variety of drugs used, the larger the dosage, the more serious the death of the fish.
The second is that the spores of sporozoites are released from the fish body into the water body, and once they are swallowed by the fish or entered from the wounds of the fish body, they continue to multiply in the fish body and break out into epidemics. Third, after the spores are released into the water body and swallowed by aquatic oligochaetes such as water earthworms, thousands of radioactive spores are multiplied in the body of oligochaetes. Released into the water body is swallowed by the fish or entered from the wound of the fish body, multiplied in the body, and the epidemic breaks out.
A large number of white wild carp iodine bubble sacs on the surface of the body of the diseased mud carp (Wang Kaiyu)
Spore onset occurs from May to October, but outbreaks generally occur from July to September, and also occur in winter.
Myxosporidium is the most abundant species of marine and freshwater fish parasites. Most of the species of myxosporidium are not harmful to fish, and only a few species cause serious epidemics, affecting the growth and development of fish.
Cake-shaped iodine blister disease often invades the visceral tissue and gills of grass carp fry in large quantities. Crucian carp unipolar insects, which often appear on the skin of carp and crucian carp, often cover the whole body with white dots or lumpy sporangia, which seriously affects the growth and development of fish, and even causes death.
Sporangiasis is a myxosporidium parasitizing on the gills and body surface of fish, growing white acne-like sporangia, piling up into a nooma, a cluster or a row of gills or fish bodies, the site of the sporangia parasitism will produce congestion, purple red or ulceration.
Some severely ill gills will be covered with sporangia, causing the gill caps of the fish to not close properly, if you open the scales of the fish, you will find that you can also see the sporangia under the scales. Fish with this disease will die of weakness, difficulty breathing, and eventual lack of oxygen.
A large number of needle-tip-sized white sacs appear on the gills of diseased carp (Wang Kaiyu)
Myxosporidiosis, in the early stages of infection, the host shows no symptoms. It is difficult to find at this stage, and only through careful microscopy can the parasitic site of myxosporids nutrients or spores and spores and sacs be found, usually in the intestines and blood of fish.
In the middle stage of infection, myxosporidium parasitizing gills, body surfaces, and finned musseozoans can be seen to the naked eye in different sizes and numbers of white or yellow sac aggregates, with a diameter of between 0.2 and 0.9 mm.
Parasitism in the gills is often accompanied by symptoms such as increased mucus, gill silk rot and swelling, parasitism on the fins is accompanied by the phenomenon of borer fins, and parasitic on the body surface is accompanied by symptoms such as rough body surface and erection of scales.
Myxosporidium parasitic in the dorsal muscles of the head and the gill arch does not form a sac, and a large number of scattered spore bodies can be seen on microscopic examination, and the parasitic sites show different degrees of uplift, soft at the bulge, and internal muscle decay.
Parasitic in the brain and other organs, anatomical parasite site may be seen white sacs. Sick fish at this stage are often accompanied by a non-hypoxic cluster floating head phenomenon at the downwind, and a small number of deaths occur.
Iodine bubble worm sac on the surface of the carp (Chen Hui)
In actual production, it is usually divided into:
Gill spores (on gill filaments) die in small amounts, laryngeal spores or cerebrospores (in the throat). Skin spores (white spores bulging in the muscles under the surface scales of the body) die in 20% to 30%. The rate of infection of peritoneal spores (intra-abdominal cavity, causing abdominal enlargement) is small. The infection rate of intestinal spores (which can block the intestine in the intestine) is very small, and in the later stages of infection, the symptoms manifested in the medium term are aggravated, the amount of death is increased, and the undead individuals are ugly or smelly .
Diseased carp gill arch large number of white wild carp iodine bubble worm sac (Wang Kaiyu)
Laryngeal spores, which are the most acute of all spore worms, the largest amount of death, the amount of harm is serious, causing the fish throat to be red and swollen and inflamed, long-term non-eating, the fish body is emaciated, the eyeball is protruding, the gill filament is swollen, the gill lid is bulging outward, it cannot be closed, it is easy to lack of oxygen, the shore floats in the early morning, and finally the sporangia penetrate the throat, and the fish body dies.
Before the outbreak, the symptoms were a large reduction in food intake or no food, and death was found in 3 to 5 days, and the roaming by the pond increased, and the number of deaths rose rapidly, and the peak of death was 10 to 15 days. Diagnostic methods can be judged based on the symptoms described above. Tissues and sacs at the site of infection can also be extracted, and the diagnosis can be confirmed by tablet microscopy finding myxosporidan bodies.
Symptoms of sick fish
Fish suffering from spore disease, due to the imbalance of the internal mechanism, loss of appetite, the skin of the fish body or gill tissue is damaged, and it is decomposed by bacterial infection, resulting in the gill tissue ventilatory function being hindered, and the diseased fish eventually dies. Sick fish, whose appearance is less severe, often rotate in waves, showing extreme fatigue and weakness.
Seriously ill fish, swimming and wandering alone in the water, often jump out of the water, and then drill into the water, so many times, and finally die, so this disease is also called crazy disease.
At present, the greater harm is crucian carp, naked carp summer flower fish species, the initial performance is a small sporangia on the gills, the body surface has a nodular protrusion, and later develops into a larger sporangia at the throat site, at this time the treatment is more difficult, often due to enteritis, bleeding, rotten gills and other complications caused by a large number of losses.
1. Skin disease caused by myxosporidium The pathogen is sulpherosporus carp. Parasitizing the subcutaneous muscles, the posterior upper end of the head of the diseased fish forms a nodular cyst, gradually expanding so that the muscles decay, the fish body darkens, emaciates, and finally dies.
2. Gill disease caused by myxosporidium Pathogens are coccidioides, special-shaped sulfonospores and so on. Silver carp, bighead carp, carp, crucian carp, etc. can be infected from fry to adult fish. There are many grayish-white dotted or noomatous sacs on the gills of diseased fish, which are difficult to breathe and hinder growth and development, causing a large number of deaths.
3. Intestinal diseases caused by myxosporidium mainly include grass fish cake-shaped sulfonabs, silver carp myxolars, symmetrical sulfonsal bubbles and so on. Its vegetative bodies form sacs in the tissue of the intestinal mucosa, and some species not only invade the mucous membrane and form sacs, but also pass through the intestinal wall and form sacs outside the intestine. It clogs the intestines and destroys tissue cells, hinders feeding, digestion and absorption and is emaciated to death.
4. Silver carp and bighead carp crazy disease caused by myxosporidium Pathogen is silver sulfonate, which invades the nervous system and sensory organs of fish. The sick fish is extremely emaciated, the body color is gray and dull, and the white putted cysts can be seen in the brain cavity. The tail is upturned, swimming wildly, convulsing and whirling, losing its balance, sometimes sinking to the bottom of the water, sometimes lying on the surface of the water, and soon dying.
In addition, the sticky robe worm often invades the liver, kidneys, spleen, heart, reproductive glands, bladder, fat and other tissues and organs of the diseased fish, causing different degrees of lesions.
Prevention and control of myxosporidiosis
For the treatment of sporangiasis drugs, there are many types of external and internal drugs for the treatment of sporeworm disease on the fishing drug market, which have a certain curative effect, but they cannot effectively kill the spore sporangia, only kill the nutrients of the spore worm to achieve the purpose of treatment. There are few external drugs that can effectively expel the body surface, supra-gill sporangia sacs, and control the development of spore worms in vivo.
1. External medication:
(1)０． 1% concentration of crystalline dimethopods soaked for 10 min.
(2) 10ppm potassium permanganate soak for 15 min.
(3) Use the crystal enemy insect 0.5-3ppm whole pool to sprinkle, and use it again every other day, or even three times.
(4) 80% of the dichlorvos 10ppm soaked to bran or drum skin feeding, for 3 consecutive days, and sprinkled with 0.5-3ppm dichlorvos;
(5) For every 10,000 fingerlings or 10 kg of edible fish, feed them with 75g of sulfur powder mixed with bait, once a day for 8 consecutive days.
(6) The whole tank is sprinkled with crystal enemy insects 1.2ppm plus 0.7ppm copper sulfate compound once,
(7) Commercially available drugs that kill myxosporidium.
2. Internal medication:
With 0.15% to 0.2% levamisole hydrochloride or 0.15% to 0.2% chlorphenidine hydrochloride bait for 5 to 7 days.
(Liu Wenjun, June 28, 2017)
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