Types of parasites in the human body: classification, description, methods of control and treatment

parasites in the human body

There are zoological and ecological classifications of parasites.

zoologicalThe classification establishes the parasite's belonging to certain systematic categories: type, class, order, family, genus.

environmentClassifications are based on the characteristics of the parasite's lifestyle.

  • specific parasites.parasitize on only one species of animal (pinworm, dwarf tapeworm, louse);
  • non-specific parasites- Parasites on various animal species (mosquitoes, tapeworms, trichinella).

Depending on the localization of the parasite in the host organism:

ectoparasites-parasitize on the outer skin of the host ( blood-sucking arthropods);

endoparasites- the habitat is the host organism:

  • in the abdominal organs connected to the external environment (digestive, respiratory and genitourinary systems) - ascaris, pulmonary flukes;
  • in tissues (musculoskeletal system, subcutaneous fat) - guinea worm, trichinella;
  • intracellular (malarial Plasmodium);

transitional forms.For example, in the stratum corneum, the epidermis parasitizes itching, which breathes atmospheric oxygen.

Depending on the degree of connection between the developmental cycle of the parasite and the host organism:

  • persistent parasites- The entire cycle of development takes place in the body of an owner (trichomonas, scabies, lice);
  • temporary parasites- only part of the development cycle takes place in the host organism (blood-sucking insects, worms).

By the number of hosts that change regularly in the development cycle:

The host is a living organism used by the parasite as a source of food and habitat.

host classification

Hosts are divided intofinal, mediumandReservoir.

Final (fundamental, final)- Hosts in whose organism the parasite is in the sexually mature stage or reproduces sexually (malarial mosquito for malaria Plasmodium, human for sexually mature pork tapeworm).

intermediate- Hosts in which the parasite is in the larval stage or reproduces asexually (humans in malaria Plasmodium; pigs, wild boars in tapeworms).

reservoir- Hosts that are not obligatory in the parasite's life cycle, but once entered the organism, on which the parasite does not die, although it does not undergo further development. Parasites accumulate in the reservoir host. When the reservoir host is eaten by the definitive host, the parasite completes its development inside its body. For example, a broad tapeworm can parasitize in the human intestine. For him, man is the ultimate master. There are two intermediate hosts in the development cycle: the first is the cyclopean crab, the second is many species of fish. However, non-predator fish can be eaten by predatory fish, such as pike. In this case, the helminth larvae do not die, but accumulate in the muscles of the pike, becoming a reservoir host.

In this way,the host organism is a kind of habitat for the parasite.The doctrine of the host organism as the habitat of the parasite was most fully developed by academic E. N. Pawlowski.The totality of all organisms that live in one organism at the same time is called parasitozoenosis.

parasite classification

Depending on the degree of need for the species to lead a parasitic way of life:

  • false parasitism- Single individuals of a free-living species accidentally enter the body of another species, remain viable there and cause disturbances in the normal life of the host. After brief parasitism in the host organism, false parasites die or are released into the environment. For example, coprophilic amoebas can live in feces. When the feces dry up, they cyst. Cysts of coprophilic amoebas can accidentally enter the human intestine. Normally, cysts pass through the intestines and are excreted into the external environment with the feces. In some cases, amoebas arise from cysts in the human intestine and become parasitic for a short time, causing acute digestive disorders.
  • Optional parasitismsuggests the possibility for a species to have both a free and a parasitic lifestyle. In this form of parasitism, wild species that accidentally invade another species' body temporarily use it as a habitat and food source. Compared to pseudoparasites, facultative parasites remain longer in the host organism. An example of facultative parasitism is the free-living amoeba of the generanailleriaandacanthamoeba. Negleria and Acanthamoeba live in bodies of water that receive sewage. If they enter the human body through the mouth or wounds on the skin, they can cause severe amebic meningoencephalitis, which is sometimes fatal.
  • True (obligatory) parasitism- A parasitic way of life is mandatory for at least one of the stages of development. Real parasites are trypanosomes, leishmania, malarial plasmodia, pork and beef tapeworms, ascaris and many other types of living organisms.

Depending on the localization of the parasite in (on) the host organism:

  • ectoparasiteslive on the host's body surface and feed on either their blood (hematophages) or the stratum corneum and its derivatives (keratophages). Human ectoparasites are usually insects and mites. Ectoparasites are often also specific carriers of human pathogens.
  • Parasites that live in the cells, tissues and cavities of the host body are calledendoparasites. Accordingly, localization distinguishes intracellular, tissue and cavity parasites. Endoparasites can affect any organ. There are intestinal parasites (tapeworms and roundworms, protozoa), parasites of the liver (flukes), parasites of the lungs (lung flukes), urogenital system (schistosomes, trichomonas) and other organs. The parasite can be localized in only one organ or infect different organs of the host.

Depending on the time of contact of the parasite species with the host:

  • Temporary parasitesThey usually parasitize on the host's outer skin (ectoparasites). They are connected to the host organism only through food chains (e. g. hematophages), and the time of their contact with the host is much shorter than the time of free life.
  • stationary parasitesspend a long time, sometimes their whole life, in (at) the owner. For stationary parasites, the host organism is not only a source of food, but also a habitat. Stationary parasites include almost all endoparasites and some ectoparasites. Stationary parasitism includes two forms of parasitism:periodically(the parasite spends part of its life in the external environment) andconstant(the parasite does not leave its hosts). Periodic parasitism is more common in nature than permanent parasitism.

By specificityParasites are divided into monospecific and polyspecific.

  • Parasites adapted to life in organisms of different biological host species are namedpolyspecific. A variant of polyspecificity is polyphagy - the ability of blood-sucking parasites to feed on the blood of hosts of different species. For example, the sexually mature stages of the liver fluke (liver fasciola) parasitize various herbivores; many mosquito species (familiesCulicidae) feed on the blood of hosts of various mammalian species.
  • If a parasite is adapted to life in a particular host type, it ismonospecific. A variant of monospecificity is monophagy - the feeding of blood-sucking parasites at the expense of hosts of the same species. An example of monospecificity is the parasitization of human lice of the specieshuman pedicle. Once on the surface of the body of another species, these lice die. Askaris Human (Ascaris lumbricoides) are also monospecific parasites. Once inside the bodies of other hosts, they die before reaching puberty.

What parasites live in the human body

The internal flora of man is an excellent environment for habitat and active reproduction of microorganisms belonging to the pathogenic group. Types of parasites in the human body are usually divided into two options - those whose presence is imperceptible and has little effect on overall health, and those whose presence can be harmful. Throughout their lives, they are able not only to negatively affect the organs, but also to release toxins that poison all living things.

Most of the parasites in the human body are worms of the nematode group, which are diagnosed in both adults and children. Parasites can vary in location (in the gut, liver, heart, and even brain), size, life cycle, and even the length of time they are in the body.

The most common types of parasites affecting humans - nematodes - are the following.

This microorganism parasitizes in the walls of the large intestine while spreading the eggs of its future offspring outside of the large or small intestine, for example on bed linen. Most often this parasite is diagnosed in children. Worms cause itching in the anus, decreased appetite, grinding teeth during sleep, and fatigue.

The life cycle of microorganisms is about a month and they reach a size of 12 mm. Pinworms are very resistant to the external environment, the appearance of new species occurs as early as 6 hours after egg laying.

These helminths live in the body of cats and dogs and, through contact with these animals, get into the internal environment of humans. This type of intestinal parasite can reach 3 cm in length and can be found in all internal organs and vessels without going outside.

They are among the most dangerous infectious parasites in humans. Grows up to 3 cm long and can live a long cycle. They penetrate into all organs of the system and at the same time actively multiply.


Parasitic invasion caused by Trichinella can lead to negative consequences: edema, fever, dermatitis, indigestion and all kinds of allergies, including food allergies. The main difficulty in detecting these helminths lies in their microscopic size, which is usually no more than 4 mm. The worm, which lives in the intestines, can penetrate the blood vessels, through which it spreads throughout the body via the bloodstream and settles in every organ.

Trematodes also live quite frequently in the human gastrointestinal tract. They are distinguished by a flat shape and the presence of suction cups. These extra organs are necessary for them to stick to human organs in order to suck out useful substances from them.

The classification of parasites by type of helminths includes a class of trematodes, consisting of the following microorganisms:

  • Opisthorchis is a simple parasitic worm that often lives in the stomach, gallbladder, pancreas and liver, leading to the development of gastritis, ulcers and pancreatitis. The intestines in any form as such interest him little;
  • Strongyloid - intestinal acne, is a worm up to 2 cm long that affects the gastrointestinal tract. Its lifespan is not long, but at the same time its activity manages to lead a person to asthma, gastrointestinal disorders, bronchitis, asthenia and other diseases.

Since trematodes have access to all human organs and tissues, invasion by them is considered the most common and most difficult to treat.

These microorganisms engulf a vast amount of tissue and blood, often knocking out the circulatory system.

Of all the parasites living in humans, cestodes are the most dangerous. The length of this helminth can reach 10 m, if you think about what kind of parasites live in the human body, it is difficult to imagine such a huge worm that can fit in the human body. They mainly get inside when eating contaminated meat.

The most common types of cestodes are:

  • Pork tapeworm - grows up to 8 m in length, at first there are no symptoms of invasion, later the activity of pork tapeworm leads to intestinal obstruction. It is also possible to develop asthenia;
  • Beef tapeworm - can grow up to 18 m in length and provokes dangerous diseases for humans, including anemia, intestinal obstruction, allergies, gastrointestinal diseases and, as a result, the nervous system;
  • broad tapeworm - the length of this parasite reaches 8 m. One of the few parasites in humans that lives in the small intestine. Causes anemia, asthenia, problems with the digestive tract and intestinal obstruction;
  • Echinococcus - is considered the most dangerous tapeworm, the infection of which at the initial stage does not show any symptoms. However, too rapid spread of the worm throughout the body leads to the formation of tumors.


Thinking about what kind of parasites are in the human body, do not forget about the possibility of infection with the so-called protozoa. This class of microorganisms has nothing to do with the three groups of helminths, as it represents its own special species of parasites that live in various human organs.

Protozoa belong to the class of endoparasites, which can be located in almost any corner of the body. This species got its name for a simple structure consisting of just one cell. However, they can cause various dangerous diseases in the human body.

The main types of parasitic protozoa:

  • trichomonads. Despite the presence of only one cell, they have a very complex structure. Depending on the degree of localization, there are several types of parasites of this species: oral, intestinal and vaginal. The most common infections that occur in the presence of this organism in the reproductive system. Trichomonads often lead to prostatitis in men. Affect the brain and nervous system;
  • Lamblia. Localized in the gut. They lead to dysbacteriosis, gastrointestinal disorders and general intoxication of the body. Usually attached to the mucous membrane of the duodenum, where they actively multiply;
  • Amoeba. Can cause asthenia and indigestion, and also cause intestinal obstruction;
  • toxoplasma. This parasite is very dangerous for a pregnant woman, as it can provoke miscarriage in the early stages. In addition, Toxoplasma causes diseases of the eyes, nervous system and heart.

A special danger of infection of the human body with protozoan unicellular microorganisms is that the developing infection in most cases is asymptomatic.


This type of parasitic microorganisms, such as ectoparasites, form their own group of dangerous carriers of infection. This class is distinguished by the fact that its representatives are localized exclusively on the surface of human skin, but they can infect them with such dangerous diseases as anthrax, typhoid, encephalitis, trypanosomiasis and others.

It is not difficult to recognize the appearance of parasites from this group, since they usually cause noticeable discomfort to their host. The main consequences of their bites are the appearance of allergic reactions, itching and burning.

Dealing with such microorganisms is only possible with special means. In addition, hygiene of the premises, bedding and clothing is usually required. Very dangerous ectoparasite of an exotic species that can be introduced when travelling. The bites of some of them can be deadly.

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The fight against parasites in the human body, regardless of their location, should be carried out comprehensively and in consultation with the doctor. But the important point is the correct diagnosis of infection with dangerous microorganisms.

Usually the symptoms that the human body has been susceptible to parasitic infection are the following:

  • Constipation - due to intestinal obstruction associated with large worms. In addition, helminths are able to block the flow of bile, which causes painful discomfort in the lower abdomen.
  • frequent gas formation - usually caused by worms that have settled in the small intestine. This also includes the so-called irritable bowel syndrome;
  • Diarrhea - liquefaction of feces is caused by special substances secreted by some microorganisms. Too frequent loose stools can indicate an infection;
  • allergic reactions - usually occur to the waste products of microorganisms inside a person. It is also possible the appearance of eczema and skin rashes;
  • Pain Discomfort in the joints and muscles. If this sign appears for no apparent reason, then checking for the presence of parasites is mandatory. Some of them prefer to live exclusively in synovial fluids and muscles, and pain is an immune response to the appearance of microorganisms.
  • Weight jumps, loss of appetite - are associated with intoxication of humans from parasitic waste and glucose starvation;
  • Chronic fatigue syndrome, sleep disorders, anxiety and irritability. He says more often that the body's resources are depleted due to the violent activity of parasites in it.

There are many types of parasites that can live in the human body. Most infections in the early stages are completely asymptomatic. However, treatment of the parasitic invasion in the early stages is considered the most effective and simple.

What types of parasites live in the human body?

Creatures that live in the body of animals, humans, birds and fish and feed on their host are called parasites.The vital activity of such organisms in the human body does not lead to anything good, parasites can cause serious complications and even death. Consider in more detail the types of parasites in the human body. Below is a detailed classification of parasites.


  • The simplest - these include Giardia, Dysenteriamoebe, Trypanosoma, etc.
  • Roundworms - Roundworms and pinworms take root well in the human body
  • Flatworms - the human body is an excellent place for pork and beef tapeworms, liver flukes, etc. to live.
  • lice and fleas
  • ticks and brakes

It is quite difficult to deal with such parasites, since throughout their life they reliably attach and attach themselves to the walls of organs with the help of special suction cups and hooks.

Some individuals can live in cells and tissues in general and from there it is almost impossible to get them out. It's about worms. The situation is somewhat simpler with insects, as they are mostly found on the surface of the body, where they can be identified and destroyed in good time.

What parasites live in the gut? So, let's analyze each of their varieties and places where parasitic worms and protozoa live.


This type of parasite in the human body is also very dangerous. These worms are called flatworms because their body shape resembles flat ribbons. There is also the most harmless type of flatworm for humans - these are ciliary worms. But let's talk in more detail about dangerous parasites - flukes and tapeworms.

Flatworms of this species are small, but very firmly attached to the walls of human organs thanks to their suction cups. The fluke, which parasitizes mainly in the liver and intestines, causes anemia, constant headaches and sudden weight loss. This worm can invade the lungs and even the brain during its lifetime and cause serious consequences. The source of leeches is dirty water and plants.

This type of worm has a very large length and is constantly growing to its full potential. A tapeworm can grow up to 6. 5 meters in its lifetime. Representatives of tapeworms - beef and pork tapeworm - can reach a length of up to 10 meters. Parasites live in the human gut, specifically the small intestine. The most dangerous type of tapeworm is Echinococcus, which can infect the brain and lungs.

Losing weight with a normal appetite is the main sign of tapeworm infection.


These types occur mainly in children - kindergarteners and elementary school students. The most popular are roundworms, which are pinworms and roundworms, both of which tend to parasitize in the intestines.

These types of parasitic worms do not adhere to the walls of human organs in any way, as roundworms do not have adaptations for this, however, they are not easy to remove. Pinworms tend to lay their eggs in the folds of the anus, causing unbearable itching in the perianal area. Children become infected "in a circle" - scratching the itchy spot, pinworm larvae remain on the hands and under the nails, and if the child accidentally puts his fingers in his mouth, the infection reappears.

And if the symptoms appear occasionally, then people in the modern rhythm of life simply do not notice them or attach great importance to them. And very in vain. There are many terrible and irreparable consequences.

Experts recommend getting tested for parasites at least once a year - feces, blood. Because only the timely detection of parasites in humans and competent treatment ensure further quality of life.

What happens to a person in whose body parasites live for a long time?

  • Powers are exhausted as parasites multiply and grow.
  • Immunity is greatly reduced, as the body puts all its strength into fighting pests.
  • Any, even the simplest virus or infection can infect a person, since the body cannot protect itself from viruses.
  • In the course of their lives, parasites excrete toxins that gradually accumulate in the human body. It is gradually poisoned, which is fraught with various infectious diseases and even malignant diseases.


Prevention is an essential part of pest control. It was said above what parasites are in the human body. As for worms and protozoa, modern medicine offers a wide range of drugs for the prevention and control of pests.

But you should not prescribe the drug yourself, you must first consult a specialist, especially if you are worried about any symptoms. After conducting the necessary tests, the doctor himself will prescribe the right drug, depending on what parasites live in the human body.

After all, each drug acts on certain types of parasitism, unfortunately, there is still no universal one. And it is a specialist who will help you choose a medicine that is relevant in this case, that will fight a certain type of parasite in a person.