Myxosporidia

Myxosporidia are parasites that are typical for fish. They do not always cause harm to their hosts, but their presence in large quantities can provoke the development of serious diseases in fish.

Myxosporidia do not pose a danger to the human body.

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Type of myxosporidium

Myxosporidia have many varieties that affect fish depending on their species. Fish become infected with protozoa by ingesting their cysts.

Fish of the flounder family are most susceptible to infection, and further down the list myxosporeans are found less frequently:

• family of flounders;
• family of stags;
• cod family;
• family of greenlings;
• family Chanterelle;
• family of herring;
• family scorpionfish;
• family of mullet;
• salmon family;
• family of carp;
• family of eelpouts, etc.

Some varieties of myxosporeans are found in cartilage, others in the outer covering or in the connective tissue layer. Parasites can be observed in the muscle tissue of fish: they look like small cysts. In frozen fish, spores can remain viable for many months, while their numbers remain unchanged. After the death of the host fish, the infected muscles undergo a stage of histolysis, after which they soften, become jelly-like, and as a result acquire the appearance of a viscous homogeneous substance. Therefore, the quality indicators of such fish are constantly deteriorating.

Life cycle of myxosporean

How does the development cycle of myxosporean occur? How does the parasite end up in the fish's body?

Myxosporidia are spread by spores, which are the main link representing the life cycle of myxosporidia.

Spore formation occurs in the endoplasm of the parasites. Depending on the size of the plasmodia, they can form from two to several thousand spores.

The structure of myxosporean is very complex and at the same time very unique. Externally, the spore is covered with a dense bifoliate shell. The valves have a visible connection - a seam. In this area, the valves touch each other, resembling two watch lenses, closed at the edges. The valves can have different shapes, and in many cases they have processes of different configurations and lengths.

In the middle of the valves on the back surface of the spore there is a small amoeba-like embryo, which, as a rule, has two nuclei. In the front part (or along the border of the seam) there are a pair (or 2 pairs) of stinging capsules. Such a capsule is represented by a peculiar bubble with liquid contents, covered with its own layer of shell. Inside there is a spirally wrapped oblong thin thread. Its length can be many times greater than the total length of the spore. Such a thread is of great importance in the defeat of fish by myxosporidium.

The development cycle of a spore is complex. Six nuclei are involved in the formation of each structure, of which two form amoeboids, two form valves, and the remaining two contribute to the formation of stinging vesicles.

Mature spores can enter the water body in various ways:

• cavity myxosporeans are excreted through the intestines and kidneys;
• tissue myxosporeans – with disruption of the integrity of the cyst and the formation of ulcerative surfaces.

Some types of myxosporeans release spores only after the death of the host, such as parasites that live in cartilage and nerve fibers.

When a fish swallows a spore, the stinging threads are released by digestive enzymes and penetrate the intestinal wall. There, the spore is fixed in the host's body, after which the valves open along the suture border, the amoeba-like embryo leaves the spore and freely penetrates the tissue. Subsequently, the embryo reaches the organ that is most suitable for this type of myxosporean from tissue to tissue.

The described life cycle of myxosporean is very unique and does not repeat the development cycles of other sporozoans. The structure of the structures is also very characteristic.

Myxosporidia in humans

When dead fish rot, the spores come out and end up in the water, where they are swallowed by healthy fish. Myxosporidia are a common cause of diseases and mass deaths of fish. Parasites are often found in edible fish, which is a reason for rejecting such fish products. However, the spores (capsules) are easily removed from the fish carcass, which may subsequently be quite suitable for consumption. When examining the composition of the capsules under a microscope, spores inherent in myxosporidia can be observed. These protozoa cannot parasitize in any form in the human body, as well as in the bodies of mammals and birds. For this reason, myxosporidia do not pose a danger to humans.

Treatment of myxosporidia

Despite the fact that myxosporeans are considered to be the causative agent of serious diseases in fish, infection with them is currently not amenable to certain treatment methods. It is recommended to combat myxosporeiosis using only preventive measures in fish farms, ponds or fish factories. Of course, myxosporeans cause great damage to the fishing industry, negatively affecting the marketable appearance and taste of fish. However, there is still no special treatment regimen for myxosporeans.

Prevention of myxosporidia

Prevention of myxosporidia in fish farms is aimed at removing fish infected with myxosporidia from the reservoir, cleaning and summering. They use a complete drain of water and cleaning (in the warm season) the bottom of the reservoir from flora, roots, etc., put in order hydraulic structures, disinfect tributaries and channels. Under the influence of solar radiation, disinfectants and drying, myxosporidia die or lose their viability. In addition, during cleaning, the bottom of the reservoir is saturated with oxygen, mineralization of organic matter occurs, and the natural fish productivity of the reservoir increases.

Due to the safety of myxosporean bacteria for humans, preventive measures for eating contaminated fish have not been established.