The most dangerous parasites in sea and river fish

Fish is considered a healthy, mineral-rich food. Since the beginning of the 21st century, food made from raw, pickled, and salted fish has become quite famous. Eating raw food puts a person at risk of some kind of infection. Smoked fish may contain parasites. In this case, helminths pose a danger to the human body. There are worms in fish that do not pose a danger, but there are also those that have every chance of causing significant harm. The danger of infestation from fish in humans is great.

What worms do crucian carp have?

Crucian carp is a freshwater fish, which means that it is much more likely to become infected with worms than marine inhabitants.

The most common parasites:

1. Wide tapeworm - a flatworm, the larvae of which, penetrating into the human body during poor-quality processing of the catch, cause a sharp increase in body temperature, headaches and painful discomfort in the abdomen. Long-term treatment for this helminth can lead to cirrhosis of the liver and even death.

2. Ligula vulgaris is a tapeworm that reaches a width of up to 4 centimeters and a length of up to 0.8 meters.
3. The cat fluke or Siberian fluke is a parasite from the group of liver flukes that enters fish through river mollusks. A person becomes infected by eating improperly cooked fish. The worm affects the liver and pancreas, which leads to severe and irreversible consequences in the body and even death.
4. Anisakiasis - the larvae of this parasite are very dangerous for humans. This type of worm lives in the peritoneum of fish.
5. The Chinese fluke is a liver fluke; in an uncomplicated form of the disease it causes intestinal disorders; severe pathology causes damage to the liver and pancreas.
6. Pinworms are small-sized (up to 1 cm) worms that parasitize in the lower parts of the intestine (usually in the rectum). A person experiences severe itching in the anal area, which intensifies at night.
7. Trematode Metagonimus yokogawai , reaching up to 2.5 centimeters in length. It causes a serious disease - metagonimiasis, which is accompanied by intestinal disorders, and in severe cases, affects the brain.
8. The cestode of the genus Diphyllobothrium is a tapeworm that grows up to 10 meters in length and causes a dangerous disease for humans - diphyllobothriasis.
9. The tapeworm Bothriocephalus gowcongensis , up to 35 centimeters long, is relatively harmless to humans because it affects fish more.
10. The nematode Philometroides lusiana is a red helminth, safe for humans, that parasitizes the scales, swim bladder, scale pockets, and kidneys of carp fish. Causes enormous damage to fish farming farms.
11. Trematodes and flatworms causing various types of diplostoma . Pathological changes can be found in various parts of the fish’s body.
12. The helminth Philometra fasciati is a red worm up to 10 centimeters long. After their removal, the fish, having undergone thorough heat treatment, is suitable for consumption.
13. The trematode Opisthorchis felineus is the causative agent of the dangerous parasitic disease opisthorchiasis. Its focus is in the area of ​​the liver, pancreas, and bile ducts. In an advanced stage, it can cause severe liver damage.

Parasites localized in fish are dangerous not only because they cause diseases of its internal organs, but also because they can infect a person who eats it without first thermally treating it. But in addition to dangerous worms for humans, crucian carp also contain worms that are relatively safe for humans, with which the fish itself is infected.

Did you know? According to estimates by the World Health Organization, a huge number of people on the planet are infected with one of three types of parasitic worms. 1 billion 200 million people suffer from enterobiasis, 700 million from trichocephalosis, and 900 million from hookworm.

Security measures

In order not to become infected with dangerous parasites (as you may have already seen, there are a lot of them in fish), a person first of all needs to give up the habit of eating the meat of aquatic inhabitants raw. Most often it is found in oriental cuisine, so despite the desire to enjoy the taste of the delicacy, it is best to abandon it in favor of traditional boiled or fried fish. Let's highlight some recommendations from professionals:

• A complete ban on adding raw seafood to the diet.
• Fish dishes should be cooked at temperatures above 60 °C for a long time. In this case, all helminths will die.
• Cold smoking and salting do not allow you to completely get rid of the parasites existing in fish, so it is undesirable to resort to them.
• Sea fish must be frozen after catching, and then, once defrosted, cooked immediately. Its storage is highly undesirable.
• River fish should be cooked, boiled (at least 1/3 hour) or steamed, fried.
• Fish pies and pies are baked for at least 30 minutes.
• It is best to cut the meat into small pieces.
• Advice to housewives: you should not try uncooked fish meat while preparing a dish.

It must be remembered that in most cases, helminth larvae are not visible to the naked eye, so if a person does not notice them, this does not mean that they really are not there.

Diseases from eating fish with worms

Parasites that live in fish are dangerous because they provoke dangerous diseases in humans. The most common way worms enter the body is through poor heat treatment and failure to comply with personal hygiene rules when processing fish.

Worms are the causative agents of many dangerous diseases. These include:

• metagonimiasis , which causes intestinal disorders;
• opisthorchiasis - affects the liver, pancreas, gall bladder;
• clonorchiasis , affecting the liver, gall bladder and their ducts; may be accompanied by allergic rashes;
• diphyllobothriasis - accompanied by serious gastrointestinal disorders, worsening apatite, general weakness;
• nanophyetosis - stable intestinal disorders, in severe cases - anemia;
• anisakiosis - various intestinal disorders, allergic reactions, in advanced form can cause peritonitis due to intestinal contents entering the peritoneum;
• ligulosis - tapeworms, increasing in size, compress internal organs in their habitats; In addition, the body receives fewer nutrients.

Crucian carp, like other river fish, is more prone to helminthic infestation than marine life. This is due to the fact that salt water is not a very comfortable habitat for parasites; they feel better in fresh water bodies.

Important! Opisthorchiasis can also be contracted from domestic animals, in particular from cats. Therefore, do not give your pet raw fish, but only heat-treated fish. This dangerous disease can lead to complete destruction of the liver.

It’s easy to get infected with worms; you should try raw fish once . However, it is possible to know for sure that an infection has occurred only with the help of laboratory tests. Therefore, if after eating fish you feel constant weakness, causeless nausea, there is an upset bowel movement and allergic reactions that did not exist before, it is better to consult a doctor and be examined for the presence of worms in the body.

Opisthorchiasis

The habitat of opisthorchiasis worms in fish is the gills and muscles . The disease is caused by the Siberian fluke. After entering the human body, it moves to the liver, pancreas or gall bladder, where it begins to parasitize. This leads to the release of a huge amount of toxic substances into the blood. Various rashes often appear on the skin, which are one of the symptoms of infection with this parasite.

Did you know? Parasitic worms, in large quantities, are capable of sucking up to half a liter of the “host’s” blood per day. Therefore, a person infected with worms loses weight very quickly.

The size of the worm is small, about 12 mm. In addition to fish, it also parasitizes mammals. The disease appears 20-21 days after a person has consumed contaminated products . The temperature rises, weakness appears, the person complains of nausea, and in some cases, vomiting, and a constant headache appears.

The patient has difficulty breathing and often develops a cough. Sometimes the body temperature reaches +40°C. With repeated infection, the symptoms do not appear so clearly, which carries additional danger. The liver and spleen are severely affected. Opisthorchiasis cannot be treated without a doctor's prescription and using traditional methods . This is fraught with the appearance of complications and the transition of ailments to a chronic form.

Crucian carp is a carrier of the infection, and helminths are parasitic in the human body, or in the tissues and organs of domestic animals that have eaten infected fish.

Clonorchiasis

Crucian carp can be a carrier of another disease - clonorchiasis , which is caused by the Chinese fluke. Infection occurs when eating undercooked or poorly fried fish.

Important! With helminthic infestation, rashes often appear on the skin, which many often confuse with allergies. Therefore, when various types of rash appear, it is advisable to check for the presence of parasites in the body.

The disease is detected by identifying eggs in the contents of the duodenum or in stool. The disease is treated with medications such as Praziquantel or Albendazole. The dosage of these drugs is determined by the doctor. Self-medication is not allowed.

The disease is severe because it is infected with the liver fluke (Clonorchis sinensis), which settles in the liver and gradually destroys the gland . When infected with clonorchiasis, the temperature rises, abdominal pain, nausea or vomiting, general weakness and loss of strength, and mild jaundice appear. Sometimes the symptoms are not particularly pronounced.

1 – definitive host, 2 – egg, 3 – miracidium, 4 – first intermediate host (mollusk) 5 – sporocyst, 6, 7 – redia, 8 – circaria, 9 – second intermediate host

The parasite that causes this disease is considered the smallest of the flatworms, because its size does not exceed 2.5 millimeters . Intestinal disorders are typical for mild forms of infection; they do not pose a serious danger. If the disease is not treated, complications may occur - liver abscess, acute pancreatitis and stones in the hepatic ducts.

Atrophy of the liver parenchyma and portal fibrosis - develops with massive proliferation of parasites and the chronic stage of the disease in the absence of treatment. When worms accumulate in the bile ducts, Botkin's disease may occur . Advanced forms are accompanied by the development of purulent diseases of internal organs, and sometimes cancer.

We recommend reading how to take dill seeds for worms.

Metagonimiasis

Another type of worms that is transmitted through river fish is metagonimiasis . Trematode (Metagonimus yokogawai), parasitic in the small intestine, is no more than 2 mm long and up to 0.8 mm wide. Its oblong-oval body is covered with tiny spines. It produces eggs with a lid. Symptoms of the disease appear 1-2 weeks after infection with worms. This could be stomach pain, gastrointestinal disorders, or general weakness of the body.

The life cycle of a parasite occurs with the participation of more than one host. The helminth carrier (human or animal) releases eggs with feces, which, when released into the water, are absorbed by mollusks (intermediate host).

In their organisms, the eggs turn into cercariae, which leave this host and attach to the scales and other organs of crucian carp or cyprinid fish. They are another intermediate host. When a person or animal eats poorly thermally treated infected crucian carp, infection with metagonism occurs.

Did you know? Diphyllobothrium Saturn is the longest tapeworm. The parasite can reach 12 meters. It lives in the intestines of fish, but sometimes parasitizes humans.

It is also possible for it to get from the scales onto the hands, and with poorly washed hands into the human body . Worms penetrate the mucous membrane of the small intestine, causing inflammation, epithelial atrophy, and intestinal disorders with prolonged diarrhea. May lead to anemia. You can only find out about infection with this helminthic infestation by examining excrement and clinical signs. To avoid becoming infected with trematodes, you should eat only heat-treated, well-cooked or fried fish, and also avoid eating dried fish. After cutting the product, be sure to wash your hands thoroughly with soap.

Parasites of natural populations

When pink salmon grow in seawater conditions, the species diversity of the parasitic fauna can be much greater than when grown in closed reservoirs. The most common types are the following:

• Microsporidia. Protozoan parasites that are related to fungi. Capable of forming spores that settle in muscle tissue and in the heart. Sometimes the number of infestations, according to studies by parasitologists, reached 938 cysts.
• Myxosoma. Myxosome spores are very resistant to drying out: they can survive without water for up to 10-15 years. The destruction of fish cartilage tissue progresses. Affected specimens exhibit “twirling” – frequent circular movements around the tail. If the infected specimen does not die, then over time the myxosomes turn into spores and the symptoms stop. These microorganisms can only be seen under a microscope.
• Anisakids. These are small worms up to 4 cm in length. They are usually transparent. In pink salmon, it is easier to notice their whitish cysts up to 3 mm in diameter. One fish can have up to several hundred or thousands of cysts.
• Diphyllobothriidae. In fish meat, these organisms appear as small white short ribbons that move until they are cooked. Their localization is the intestines of fish.

Is it possible to eat infected fish?

Of course, the first desire of a person upon seeing a fish infected with worms will be to immediately get rid of it. But it is believed that if the number of parasites detected is small, after careful heat treatment it can be eaten. In case of heavy infection, which is visible to the naked eye, it is better to get rid of such a product .

But one moment is when a person discovers that crucian carp is infected with helminths, and another when they are so small that they are simply not visible. Therefore, when consuming any fish, especially river fish, you need to take precautions.

Important! The main sources of helminthic infestation are smoked, salted and dried fish, as well as insufficiently boiled, fried and baked fish.

In order to protect yourself from parasites entering your body, you must:

1. Keep the fish in the freezer (-18°C) for at least 48 hours. At low temperatures, worms and their larvae die.
2. Frying should be carried out for at least 20 minutes.
3. Reduce or even abandon dried or smoked fish, because the likelihood of infection with worms when consumed is high.
4. Salting should be carried out for 2 weeks.
5. Check the belly carefully - it should not be swollen.
6. If you are engaged in fishing, it is better to fish in those fish farms where the prevention of helminthic diseases is carried out.
7. It is better to buy an uneviscerated carcass so that you can see whether its insides are infected with parasites.
8. Do not feed your pets raw fish, so as not to become infected with worms from them in the future.
9. Thoroughly disinfect kitchen tools after cutting any fish, because worm eggs may remain on them, which can then enter your body.
10. Do not give raw fish with tapeworm or other infestations to domestic or outdoor animals.
11. You need to cook the fish for at least half an hour, bake for about 40 minutes.
12. Never eat raw fish, especially river fish.
13. Do not try raw minced fish.
14. Avoid contact of fish with other products.
15. It is better to defrost the product in the refrigerator.
16. Use a separate knife and board for cutting crucian carp. After cutting, thoroughly disinfect them.
17. When cooking, it is recommended to use rubber gloves.

If you comply with the above conditions for preparing fish, then the likelihood of contracting a helminthic infestation when eating it is minimized. In any case, thorough heat treatment is necessary, during which the parasites and their eggs die.

Risk of infection

Almost any adult fish has parasites. They inhabit muscle tissue, organs of the digestive system, eyes, are found on the skin, in brain structures, etc. These can be sexually mature individuals or eggs.

Parasitologists are equally interested in all parasites, but it is important to know that not all types of helminths living in red fish are dangerous to human health. From this point of view, two main types of parasites inhabiting the body of sturgeon and salmon can be distinguished:

• Parasites for which humans are an intermediate or definitive host. It is they who, after entering the body, settle in it and continue to function, develop and reproduce.
• Parasites that live in red fish, but do not parasitize the human body. Even if you eat trout, salmon, chum salmon, pink salmon and other types of red fish, such organisms will not remain in the internal organs. After digestion of food masses, they are excreted from the intestines along with feces.

Symptoms of infestation

The first clinical picture of helminthic infestation does not appear immediately and has vague signs. Symptoms depend on the incubation periods of helminth infections, which can range from 2 to 60 days. Common symptoms of parasitic infestation include:

• lethargic, drowsy state;
• excessive fatigue;
• nervousness;
• increase in low-grade fever;
• allergic reactions;
• attacks of nausea and vomiting;
• disorders in the gastrointestinal tract;
• excessive gas formation;
• jumps in weight indicators;
• depressive state.

Types of helminths that are not dangerous to humans

The eaten parasite does not always cause harm. This is due to the fact that in the chain of infection the final host of the worm is sometimes not a person, but an animal or bird.

Parasites safe for humans:

1. Diplostomum spathaceum is a representative of the class of trematodes. The larvae attack the organs of vision. This parasite usually lives in the body of silver carp and trout. Not dangerous to humans.
2. Posthodiplostomum cuticola - represents the class of trematodes (flukes). It parasitizes the body of freshwater animals; the main sign of the disease is black spots on the body.
3. Posthodiplostomum minimum is another type of helminth from the class of trematodes. The final host of this parasite is a bird, sometimes a reptile.
4. Ligula intestinalis is a representative of the class of cestodes. The definitive host of the parasite is a bird.
5. Schistocephalus sol >

Types of helminths that are not dangerous to humans

Prevention of infection

To prevent human infection with helminths, it is necessary to exclude the possibility of consuming dishes made from raw or almost raw fish (freshwater and sea) and some seafood, in particular squid. Since it is not always possible to avoid consuming fish containing parasites, the most important thing is to adhere to simple processing rules - thermal processing using temperatures above 60 ° C or long-term pre-freezing. Salting, pickling, and cold smoking are not reliable methods of prevention, but in most cases, if carried out correctly, they can also kill helminth larvae that are dangerous to humans.