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.

zoologicalclassification establishes the belonging of the parasite to certain systematic categories: type, class, order, family, genus.

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

  • specific parasites.parasitize only on one species of animals (pinworm, pygmy tapeworm, louse);
  • nonspecific parasites- parasitize on different types of animals (mosquitoes, broad tapeworm, trichinella).

According to the localization of the parasite in the host organism:

ectoparasites-parasitize on the external integument of the host (blood-sucking arthropods);

endoparasites- the habitat is the host organism:

  • in the abdominal organs associated with the external environment (digestive, respiratory and genitourinary systems) - ascaris, pulmonary fluke;
  • in tissues (musculoskeletal system, subcutaneous fat) - guinea worm, trichinella;
  • intracellular (malarial plasmodium);

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

According to the degree of connection between the parasite development cycle and the host organism:

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

According to the number of hosts that naturally change 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, intermediateandreservoir.

Final (basic, definitive)- hosts in whose organism the parasite is in the sexually mature stage or reproduces sexually (malarial mosquito for malarial plasmodium, man for sexually mature pork tapeworm).

Intermediate- hosts in whose body the parasite is in the larval stage or reproduces asexually (humans for malarial plasmodium; pigs, wild boars for tapeworms).

reservoir- hosts that are not obligatory in the life cycle of the parasite, but once in the organism of which the parasite does not die, although it does not receive further development. Parasites accumulate in the reservoir host. When the reservoir host is eaten by the definitive host, the parasite completes its development in its body. For example, in the human intestine, a wide tapeworm can parasitize. Man is the ultimate master for him. There are two intermediate hosts in the development cycle: the first is the cyclops crustacean, the second is many species of fish. But non-predatory fish can be eaten by predatory, for example, pike. In this case, helminth larvae do not die, but accumulate in the muscles of the pike, and it becomes 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 Academician E. N. Pavlovsky.The totality of all organisms that simultaneously live in any organism is called parasitocenosis.

Parasite classification

According to the degree of necessity for the species to lead a parasitic lifestyle:

  • false parasitism- individual individuals of a free-living species accidentally enter the body of another species, where they remain viable and cause disturbances in the normal life of the host. After a short parasitism in the host organism, false parasites die or are released into the environment. For example, coprophilic amoeba can live in faeces. When the feces dry out, they encyst. Cysts of coprophilous amoebae can accidentally enter the human intestine. Usually cysts pass through the intestines and are excreted into the external environment with faeces. In some cases, amoebas in the human intestines emerge from cysts and become parasitic for a short period of time, causing acute digestive disorders.
  • Facultative parasitismsuggests the possibility for a species to lead both a free and a parasitic way of life. With this form of parasitism, free-living species, accidentally entering the body of another species, temporarily use it as a habitat and food source. Compared to false parasites, facultative parasites spend a longer time in the host organism. An example of facultative parasitism is the free-living amoeba of the generaNaegleriaandAcanthamoeba. Negleria and Acanthamoeba live in water bodies that receive sewage. Entering the human body through the mouth or wounds on the skin, they can cause severe amoebic meningoencephalitis, sometimes fatal.
  • True (obligate) parasitism- a parasitic way of life is obligatory for at least one of the stages of development. The true parasites are trypanosomes, leishmania, malarial plasmodia, porcine and bovine tapeworms, ascaris and many other species of living organisms.

According to the localization of the parasite in (on) the host organism:

  • Ectoparasiteslive on the surface of the host's body, feeding on either its blood (hematophagous) or the stratum corneum and its derivatives (keratophages). Human ectoparasites are usually insects and mites. Ectoparasites are often at the same time specific carriers of human pathogens.
  • Parasites that live in the cells, tissues and cavities of the host body are calledendoparasites. Accordingly, localization distinguish intracellular, tissue and cavity parasites. Endoparasites can affect any organ. There are intestinal parasites (tape and roundworms, protozoa), parasites of the liver (flukes), parasites of the lungs (pulmonary fluke), genitourinary system (schistosomes, Trichomonas) and other organs. The parasite can be localized in only one organ or infects various organs of the host.

According to the time of contact of the parasitic species with the host:

  • Temporary parasitesThey usually parasitize on the external integument of the host (ectoparasites). They are connected with the host organism only by food chains (for example, hematophages), and the time of their contact with the host is much shorter than the period of free life.
  • Stationary parasitesspend in (on) the owner for a long time, sometimes all their lives. 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:periodic(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 species of hosts are calledpolyspecific. 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 (Fasciola hepatica) parasitize various herbivores; many types of mosquitoes (familiesCulicidae) feed on the blood of hosts belonging to various mammalian species.
  • If a parasite is adapted to life in a certain type of host, it ismonospecific. A variant of monospecificity is monophagy - 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 speciesPediculus humanus. Once on the surface of the body of any other species, these lice die. Ascaris human (Ascaris lumbricoides) are also monospecific parasites. Once in the body of other hosts, they die before reaching puberty.

What parasites live in the human body

The internal flora of people is an excellent environment for the habitat and active reproduction of microorganisms that belong to the pathogenic group. Types of parasites in the human body are usually divided into two options - those whose presence is not felt and has little effect on overall health, and those whose presence can be detrimental. In the course of their life, they are able not only to negatively affect the organs, but also to release toxic substances that poison all living things.

Most of the parasites in the human body are worms of the nematode group, diagnosed in both adults and children. Parasites can differ from each other in their location (in the intestines, liver, heart, and even in the brain), size, life cycle, and even the time during which they are inside the body.

The most common types of parasites that affect people - nematodes are the following.

This microorganism parasitizes in the walls of the large intestine, while spreading the eggs of its future offspring outside 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 in sleep and fatigue.

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

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

They belong to the type of the most dangerous infectious parasites in humans. Grow up to 3 cm in length and can live a long cycle. They penetrate into all organs of the system, actively multiplying at the same time.


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

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

The classification of parasites according to the 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, which leads to the development of gastritis, ulcers and pancreatitis. The gut in any form as such is of little interest to him;
  • strongyloid - intestinal acne, is a worm up to 2 cm long. It affects the gastrointestinal tract. His life span is not long, but at the same time, his activity manages to lead a person to asthma, gastrointestinal dysfunction, bronchitis, asthenia and other diseases.

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

These microorganisms devour a huge amount of tissue and blood, often incapacitating the circulatory system.

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

The most common types of cestodes are:

  • pork tapeworm - grows up to 8 m in length. Initially, the symptoms of invasion do not appear, but later the activity of the pork tapeworm leads to intestinal obstruction. It is also possible to develop asthenia;
  • bovine tapeworm - can grow up to 18 m in length. It provokes dangerous ailments for humans, including anemia, intestinal obstruction, allergies, gastrointestinal disorders and, as a result, the nervous system;
  • wide 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 in the first stages does not show any symptoms. However, too rapid spread of the helminth 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, since it constitutes its own special parasitic species that lives in various human organs.

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

The main types of parasitic protozoa:

  • Trichomonas. Despite the presence of only one cell, they have a very complex structure. There are several types of parasites of this type, depending on the degree of localization: oral, intestinal and vaginal. The most common infections occurring in the presence of this organism in the reproductive system. Trichomonas often lead to prostatitis in men. Affect the brain and nervous system;
  • lamblia. Localized in the intestine. They lead to dysbacteriosis, gastrointestinal upset 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 create intestinal obstruction;
  • toxoplasma. This parasite is very dangerous for a pregnant woman, because it can provoke a miscarriage in the early stages. In addition, Toxoplasma causes diseases of the eyes, nervous system and heart.

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


This type of parasitic microorganisms, such as ectoparasites, constitutes a separate 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, nevertheless, they are able to infect it 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, as a rule, they cause noticeable discomfort to their host. The main consequences of their bites include the appearance of allergic reactions, itching and burning.

To cope with such microorganisms is possible only with the help of special means. In addition, as a rule, sanitation of the premises, bed linen and clothing is required. Very dangerous ectoparasites of an exotic species, which can be picked up during travel. The bites of some of them can be fatal.

Read more: Is it possible to treat the throat of a nursing mother with the help of Lugol? Will it harm the chest?

The fight against parasites in the human body, regardless of their location, should be carried out comprehensively and in consultation with the doctor. However, 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 sizes of worms. In addition, helminths are able to block the bile streams, causing painful discomfort in the lower abdomen;
  • frequent gas formation - usually caused by worms that have settled inside the small intestine. This also includes the so-called irritable bowel syndrome;
  • diarrhea - liquefaction of feces is caused by special substances secreted by some of the microorganisms. Too frequent loose stools may indicate infection;
  • allergic reactions - usually occur on 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, checking for the presence of parasites is mandatory. Some of them prefer to live exclusively in joint fluids and muscles, and pain is an immune response to the appearance of microorganisms;
  • weight jumps, problems with appetite - are associated with human poisoning by the waste products of parasites and a lack of glucose;
  • chronic fatigue syndrome, sleep disturbance, anxiety and irritability. He says more often that the body's resources are depleted due to the vigorous activity of parasites inside it.

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

What are the types of parasites that 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 the types of parasites in the human body in more detail. Below is a detailed classification of parasites.


  • The simplest - these include giardia, dysenteric amoeba, trypanosoma, etc.
  • Roundworms - roundworms and pinworms take root well in the human body
  • Flatworms - the human body is an excellent place where pork and bovine tapeworm, liver fluke, etc. can live.
  • Lice and fleas
  • Ticks and gadflies

It is quite difficult to deal with such types of parasites, because in the course of their life they reliably settle down and attach to the walls of organs with the help of special suction cups and hooks.

Some individuals can generally live in cells and tissues, and from there it is almost impossible to get them out. It's about worms. With insects, the situation is a little simpler, since they are usually located on the surface of the body, where they can be detected and destroyed in time.

What parasites live in the intestines? 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 flatworms for humans - these are ciliary worms. But let's talk about dangerous parasites - flukes and tapeworms - in more detail.

Flatworms of this species are small in size, but are attached to the walls of human organs very firmly thanks to their suckers. The fluke, parasitizing mainly in the liver and intestines, causes anemia, constant headaches and sudden weight loss. This helminth can, in the course of its life, penetrate into the lungs, and even into the brain, causing serious consequences. The source of flukes is dirty water and plants.

This type of worm has a very large length, and it constantly grows to its full potential. In its entire life, a tapeworm can grow up to 6. 5 meters. Representatives of tapeworms - bovine and pork tapeworm - can reach a length of up to 10 meters. Parasites live in the human intestine, namely in the thin. The most dangerous type of tapeworm is echinococcus, which can affect the brain and lungs.

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


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

These types of parasitic worms do not attach to the walls of human organs in any way, since roundworms do not have any adaptations for this, however, they are not easy to remove. Pinworms tend to lay their eggs in the folds of the anus, thereby causing unbearable itching of the perianal area. Children infect themselves "in a circle" - scratching the itchy place, pinworm larvae remain on the hands and under the nails, and when the child accidentally puts his fingers in his mouth, the infection occurs again.

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

Experts recommend at least once a year to be tested for parasites - feces, blood. After all, it is the timely detection of parasites in humans and competent treatment that will ensure the further quality of life.

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

  • Forces are depleted as parasites multiply and grow.
  • Immunity is greatly reduced, as the body throws all its strength into pest control.
  • Any, even the simplest virus or infection can infect a person, since the body is not able to protect itself from viruses.
  • In the course of their life, parasitic individuals secrete toxins that gradually accumulate in the human body. It is gradually poisoned, which is fraught with various infectious 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 large selection 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 concerned about any symptoms. After conducting the necessary tests, the doctor himself will prescribe the right drug, based on what parasites live in the human body.

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