There are many species of spore worms, it is said that there are tens of thousands of species, the most abundant of which is the myxosporidium. Spores are all parasitic, and most of them are based on fish. Most spore worms do not cause a large number of fish to die, but will form sporangia of different sizes on the diseased fish, sometimes in large numbers, look very ugly and lose their commodity value, and easily cause fish to die such as iodine sporangia, coccidioides, unipolar worms, bipolar worms, quadrupolars, tailspores, myxosomes and so on.
In recent years, the incidence of fish spore disease is very high, there are many species of myxosporidium that harm fish, the insect body is relatively small, and spores are produced during development, and the parasitism of myxosporidium is very extensive, almost all kinds of fish and various organs can be infected, and even several kinds of myxosporidium parasitize in the same organ of the same fish.
life history
Myxosporidium parasitizing in fish or on the surface of the body, taxonomically belongs to the myxophyte phylum, myxosporidium, has been reported to cause disease nearly a thousand species, common and more harmful species are heteromorphic iodine bubble disease, round iodine sporangia, cake-shaped iodosporidium, wild carp iodobodonidosis, crucian iodonidosis and so on.
Each spore of myxosporidium has 1-7 pieces, (mostly 20 pieces), chitinous shell pieces, the joint of the two shells is called suture, the suture is called a suture ridge because of its thickness or protrusion. Within each spore are 1-7 (2 typical species) spherical, pear-shaped or bottle-shaped capsules with a screw-like coiled pole filament inside the capsule. The spores are filled with cytoplasm in addition to the polar sacs, which have two nucleus, and some species have an iodine-loving vesicle.
Symptoms and prevalence and diagnosis
Myxosporidium can invade various tissues and organs inside and outside the fish, so the symptoms of myxosporidosis vary according to the site of parasitism of the worm, the most obvious symptom is the appearance of white sacs visible to the naked eye in the parasitic site (body surface, gills, muscles, internal organs, etc.). At the same time, due to the parasitism of the insect body, various abnormal behaviors occur due to the discomfort of the fish body, such as rapid swimming, whirling, etc. Spore parasitism in the gills can lead to swelling of the gills, increased mucus, dyspnea in the gill filament tissue due to destruction, respiratory function, and non-hypoxic cluster floating heads at downwinds.
Laryngeal spores parasitizing the throat of crucian carp can lead to tissue hyperplasia at the throat of crucian carp and significant enlargement, making feeding difficulties in diseased fish. If the internal organs of the fish have spore parasitism, more obvious symptoms such as abdominal distension will occur. Sick fish have a decreased appetite, slow growth, emaciation of the fish, and severe refusal to eat. Once the insect parasitizes the fish body, it will destroy the function of the tissues and organs at the parasitic site, often causing local inflammation and congestion of the tissues, resulting in secondary infection of bacteria
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.
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.
1. At the beginning of infection, the host did not show any 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.
2. In the middle of infection, parasitism in the gills is often accompanied by symptoms such as increased mucus, gill silk decay 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.
3. In the later stage of infection, parasitism is in the brain and other organs, and the white sac can be seen in the anatomical parasite site. 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.
Most of the time, according to the size of the sporangia on the fish body, the naked eye can make a preliminary judgment, and if you want to further confirm which type of sporidium is caused, you need to use a microscope to observe. Sometimes sporangiasis sporangia are very small, larger on the body surface, fins appear such as corn-sized milky white sacs, or parasitized in the muscle, resulting in uneven fish body surface, or nodular protrusions, or parasitism in muscle fibers, intracranial, spine, the latter is more difficult to determine, can be combined with whether the fish swimming in the water is abnormal, whether it is emaciated to determine.
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 rate of infection of intestinal spores (which can block the intestines in the intestine) is very small, and in the later stages of infection, the symptoms manifested in the middle stages are aggravated, the amount of death is increased, and the undead individuals are ugly or smelly.
Laryngeal spores: This is 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, emaciated fish body, protruding eyeballs, gill filament swelling, gills bulging outwards, unable to close, easy to lack of oxygen, early morning shore floating head, and finally sporangia through the throat, fish body death.
Pre-outbreak symptoms: for the amount of food is greatly reduced or not eaten, death is found in 3 to 5 days, the roaming by the pond increases, the death rate rises rapidly, and the peak of death is 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.
Prevention and control of sporangiasis
For adult fish farming, the treatment of spore worms is very difficult, mainly because of the chitinous shell of the cyst formed by spores, general drugs can not penetrate into the inside of the sac and act, most of the drug treatment options are actually to prevent the development of spores infected with fish bodies to mature sporangia, reduce or control the number of sick fish spores and sacs, reduce mortality, and can not completely kill sporangia and sacs. Therefore, sporangiasis needs to be detected early, early treatment, in order to have a certain curative effect, sporangia conidia, exosporangia treatment is relatively easy, the best way to treat endosporidium is internal administration.
External use: Experienced farmers use conventional topical insecticides such as copper naphthenate, avermectin, permethrin, dimethadate, etc., internal use: chlorphenidine hydrochloride, levamisole hydrochloride, dichlorpyridolyl, etc., the effect is usually direct and significant, but the side effects on the fish body itself are also obvious, and the liver body of the fish will be damaged to varying degrees. Therefore, it is recommended to use natural and safe Maosporine for effective prevention and deworming, when severe, it can be taken internally plus external use, and when the product is spilled externally, it can be used together with povidone iodine, once or twice, if used twice, every two times at an interval of 3 days.