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This article takes ten common fish parasites as the main content, including: wheel worm, ring worm, third-generation worm, oblique tube worm, melon worm, spore worm, compound mouth fluke, anchor head ray, Chinese ray, fish fish and other insect species, according to the fish farmer can be easy to understand way, due to limited space, divided into two issues (this article is the next issue) briefly introduce its basic traits and some methods of identification, diagnosis and treatment, for reference only.
Previous issue: Common ten basic traits of fish parasites and identification, diagnosis and treatment (top) wheel worm, ring worm, third-generation worm,
Continued from the previous issue:
6. Sporozoa
There are many types of fish parasitic sporozoites, common are sticky (sticky) spore parasitizing in fish or on the body surface, taxonomically belonging to the slime phylum, myxosporidium, has been reported to be able to cause disease nearly a thousand species, common more harmful species are heteromorphic iodosporosis, round iodosporidosis, pie-shaped iodosporidium, wild carp iodosporidium, crucian iodosporidium, silver iodocystis and so on. Myxosporidium can infect fry and seed of freshwater and marine farmed fish on a widespread scale. Almost all organs of fish can be infected, and even within the same organ of the same fish, there are several species of myxosporidium parasitism.
Myxosporidium has chitinous shells, and the junction of the two shells is called a suture, and the suture is ridged due to thickness or protrusion called a suture ridge. Each spore contains 1-7 (typical species two) spherical, pear-shaped or bottle-shaped pole capsules with a screw-like coiled pole filament in the pole capsule. The spores are filled with cytoplasm except for the polar sac, which has two blastoblastocysts and an iodophilic bubble in some species.
(Idosporozoidium)
(Sporozoidium in fish)
The development process of pathogenic parasitic myxosporidium is roughly as follows: the development of Slime sporidium fish goes through the radiosporidium, vegetative body and mature spores (cysts) stages. After the spores are released from the cysts of the diseased fish body to the water body, they are swallowed by the intermediate host (generally aquatic oligochaetes), and the spores develop into thousands of radiosporidium through asexual reproduction in the intermediate host, and the radiosporidium is released into the water, and the infection is carried out when it encounters the fish body, and it is divided and developed into mature spores and cysts in the fish. The main cause of disease in fish is the cysts formed in the fish.
(Myxosporidium)
(Gill spores)
The main parasitic sites of Sporozoidium are in the pharynx, gills, squamous sacs, liver, fins, snout, intestine, muscle and other parts of fish, usually called "laryngeal spores", "skin spores", "gill spores", "brain spores", "endospores", "exospores" and so on. Among them, "laryngeal spores", "skin spores" and "gill spores" are the most common, but the harm of "brain spores" is the most serious, almost incurable, and serious can cause the collapse of the whole pond.
(Dermatospores)
(Skin spores, crucian carp is the most common)
The initial diagnosis is made by the white cysts visible to the naked eye on the body surface, body and gills of fish. The capsule can also be pressed into thin sections and examined with a microscope. Many spores can be seen under high magnification, and the diagnosis is confirmed by the appearance of the spore shell as oval, oval or oval or melon seed-shaped. Sporozoidium occurs in no obvious seasonality and can occur throughout the year, with frequent occurrences from April to October each year. In actual production, carp and crucian carp are the most susceptible, and crucian carp fry is mostly manifested in nodular protrusions on the body surface in the early stage.
Madness disease (Iodiodospora carpendum)
Sick fish with sporozoidium lose appetite, the skin or gill tissue of the fish is damaged, and it is infected by bacteria and rots, resulting in hindered respiratory function of the gill tissue. Sick fish with less severe appearance diseases tend to rotate in waves, showing extreme fatigue and weakness. Severely sick fish swim around alone in the water, often jumping out of the water and diving into the water, so many times, and eventually die, so this disease is also called crazy disease (iodospora carpinaria).
Sporozoidium breeds at night, and it is said that medication is best around 5 p.m. It is difficult to kill, and those with worm bodies in vitro and gills can be splashed with external related insecticides, and those parasitized by spore worms in vivo are taken internally to repel spore insecticides. For example: chlorphenidine hydrochloride 650 grams + levamisole 720 grams (calculated according to 98% content) mix 1 ton continuous consumption for 3-5 days; There are also dikezhuli, hundred parts of the dispersion and related insecticides. When used externally, add methionine iodine mixed with water and splash the whole pool to increase the penetration of the drug. Sporozoidium has a development time of 5~7 days from egg to adult, preventive medication must be greater than 3 days, and treatment time must be greater than 7 days to prevent recurrence.
7. Compound mouth flukes
Compound flukes are also known as "cataracts", "blind eye disease", and "eye loss disease". It can cause a large number of deaths of fry and fry, especially pelagic fish such as silver carp and bighead carp, grass carp and compound trematome of the bream are also popular. The pathogen is the cercariae and cystic larvae of the compound fluke, and the common ones are Hubei compound fluke, as well as Ni's compound fluke.
Adults of Compound Trematodes parasitize in the intestines of water birds, excrete eggs that fall into the water with feces, and hatch tricholaria. Cercariae meet the first intermediate host, the vertebral snail, and develop into cytocariae in the snail, and the larvae produce countless cercariae through asexual reproduction. After leaving the snail, the cercariae enter the second intermediate host, the fish, burrow from the skin through the blood circulation to the fisheye lens, and gradually breed cystic larvae. When the waterbirds swallow the diseased fish, the cysts develop into adults in the bird's intestines.
(Cataract)
Sick fish that parasitize compound flukes are more likely to have brain congestion, white mouth circles, protruding eyeballs or even falling off. When the fish is acutely infected, it struggles to swim in the water, and the brain area and orbit of the head of the sick fish appear hyperemic (caused by the parasitism of Hubei compound mouth fluke). If the sick fish loses its balance, lies on the surface with its head down, tail facing up, the fish trembles and gradually bends (this symptom is caused by the parasitism of Compound Flukes Ni), a large number of deaths can occur in a short time. In chronic infection, the eyeball of the sick fish is cloudy and milky white, and in severe cases, the eyeball falls off and becomes blind. During microscopic examination, the eyeball of the diseased fish is dug out, the eyeball is cut to take out the water lens, the transparent gum around the lens is peeled off, placed on a glass slide and a coverslip is added, and the diagnosis can be confirmed by checking whether there are compound trematode cysts or other parasites under the microscope.
(Drumming Eye)
Snails are intermediate hosts of compound trematodes, and polyculture of blue fish that specializes in eating snails in fish ponds is the best precaution. In addition, drugs related to kill and repel compound flukes, such as: thiodichlorophenol 20~30 grams per kilogram of fish body weight, for 2~5 days; Dibutyltin oxide takes 25 grams per 100 kg of fish body weight for 5 days; Copper sulfate 0.7 g/m³ sprinkled all over the pool, 2 consecutive sprays within 24 hours, can also kill vertebral snails.
8. Chinese Fish (Fleas)
Chinese rays are dioecious, female camps live parasitically, and male camps live freely. The female of the Great Chinese Ray parasitizes on the gills of grass carp, and the silver carp parasitizes on the gills of silver carp. The female insect hooks the gill filament of the fish with a large hook, and it can be seen with the naked eye that there are many white maggot-like insects, that is, Chinese rays, so Chinese fish disease is also called "gill maggot disease".
The Chinese ray mainly attacks the gills parasitic on the gills of fish, inserting the gill filament with its second antennae, causing mechanical damage, affecting the normal breathing of the fish, causing the fish to be restless; At the same time, the wound opens the door for the invasion of microorganisms, which can lead to local inflammation and even suppuration of the gill filament. When the mackerel worm is sucked, secreting enzymes to dissolve the tissue, so that the epidermis of the gill filament at the mouthparts is destroyed, the cells are loose, and the nearby microvessels are also destroyed, sometimes the end of the gill filament is bent and deformed, and anemia.
(The gill filaments have worm bodies and are puffy)
Great Chinese rays tend to parasitize grass carp and blue carp over 2 years old, and silver carp parasitizes on the gills of silver carp and bighead carp over 1 year old. Sick fish jump restlessly in the water, lose appetite or do not eat, and their bodies are blackened; Difficulty breathing, swimming alone, or staying in nearshore water, soon dying. When the operculum is lifted, many female rays with oocysts are visible, and the female is hung on the end of the swollen and whitish gill filament, resembling small white maggots.
In severe cases, the head is facing down and the tail is facing up, and the ends of the gill filaments of the fish are swollen and whitish. Sick fish jump restlessly in the water, lose their appetite or do not feed. After infection of silver carp and bighead carp, the tail fin often appears on the surface of the water, so it is also known as "upturned tail disease"; Sick fish often die from breathing difficulties.
The disease can be diagnosed by the naked eye, killed with a special killing of Chinese rays or insecticidal drugs, and retested after 3-5 days, and re-killing is required when the killing effect is not satisfactory.
9. Anchor head (flea)
Anchorhead rays, commonly known as anchor-headed insects, belong to the same arthropod crustaceans as the Chinese rays. Only females parasitize fish and are about 1 cm long. The posterior end of the worm body with 1 pair of oocysts. The head part has forked corners like anchors, hence the name. The tissues around the parasitism of the worm are often red, swollen and inflamed, which looks like erythema, and the scales near the wound are dissolved by the secretions of anchor head fleas (rays) and erode into gaps. When the fish is first invaded by the insect body, it shows restlessness, poor appetite, and then its body is thin and swimming slowly.
This insect can invade the body surface of carp, silver carp, bighead carp, grass carp and other fish, and even the mouth, which is particularly harmful to juvenile fish, can cause death, mainly affects the growth of large fish, and reduces the value of commodities. The disease is widely endemic and found in all fish farming areas across the country, and can be seen all year round, and can cause serious epidemics in summer and autumn.
Sick fish parasitized by anchor-headed rays are manifested in anxiety, reduced food, and emaciation. The worm parasitizes on all parts of the fish body in the shape of a white thread, swimming with the fish. Some worms have cotton-wool-like moss on their bodies, and moss, which is often mistaken for moss, hangs on fish. This pest is fierce and gluttonous, there will be irregular deep holes in the parasite, one end of the anchor head fish pierces into the fish body and one end is exposed, the head of the insect drills into the muscles of the fish body, sucks blood with the mouthparts, and also eats the scales and muscles, and the scales close to the wound are dissolved and corroded into irregular gaps by the secretions of the anchor head rays.
Only the anchor-headed fish female parasitizes on the fish body, about 1 cm long, the larvae parasitize on the fish body with erythema, visible and obvious to the naked eye, divided into three stages of children's worms, larvae and old worms, with special killing anchor head rays or related insecticidal drugs for killing, 5-10 days apart once again.
10. Fish mackerel (lice)
The fish mackerel is a small crustacean water pest. Shaped like bed bugs, commonly known as water bed bugs, also known as fish lice. The body is oval and transparent. The worm body is divided into three parts: head, chest and abdomen. The ventral surface of the head has a pair of suction cups that serve as adsorption to the body of the fish and a mouth spur that pierces the skin of the fish. The thoracic section has four segments, each with a pair of swim feet. The abdomen is unsegmented and the oval-shaped leaves are the respiratory organs of fish lice. Generally, it parasitizes all parts of the fish body of more than 2 cm of seedling, especially under the abdomen and on the fins and tail. Fish lice stab the surface tissues of fish with their mouth spikes, sucking blood and body fluids.
Fish lice do not have oocysts and the eggs are laid directly on aquatic plants or rocks. Oval in shape, yellow or brown, with a layer of gum on the outside that is fixed to other objects. At a water temperature of 29-31°C, larvae hatch in 10-14 days. After hatching, the larvae die if no host is found within two days. After leaving the fish, the fish lice can live freely in the water for a short time, so it can transfer from one fish to another on its own, and can also flow into other water bodies with the water.
Fish pediculosis is an invasive fish disease that often occurs in spring and is one of the common and frequent diseases of fish. When the fish body has fish lice parasitism, because the fish lice destroy the surface tissue of the fish body and have pain, showing extreme restlessness, or jumping out of the face, or swimming sharply, struggling and rolling in every way, it is very painful. Once the disease occurs, it is killed with a special fish and fish insecticide or insecticidal drugs, and retested after 3-5 days, and re-killing is required when the killing effect is not satisfactory.
Related Articles:
Common ten kinds of fish parasites, basic traits and identification, diagnosis and treatment (upper) wheel worm, ring worm, three generations of worm
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