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

parasites in the human body

There is a zoological and ecological classification of parasites.

zoologyclassification assigns parasites to specific systematic categories: type, class, order, family, genus.

environmentclassification is based on the characteristics of the parasite's lifestyle.

  • certain parasites.parasitic on only one species of animal (pinworm, pygmy tapeworm, flea);
  • non-specific parasites- parasites on various types of animals (mosquitoes, tapeworms, trichinella).

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

ectoparasite-parasites on the external integument of the host (blood-sucking arthropods);

endoparasites- habitat is the host organism:

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

transitional form.For example, in the stratum corneum of the epidermis, the itch becomes a parasite, which inhales atmospheric oxygen.

According to the degree of relationship between the developmental cycle of the parasite and the host organism:

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

According to the constantly changing number of hosts in the development cycle:

A host is a living organism that the parasite uses as a source of food and habitat.

Host classification

The host is divided intoend, middleandreservoir.

Final (basic, final)- the host in whose organism the parasite is sexually mature or reproduces sexually (malaria mosquito for malaria plasmodium, male for sexually mature pig tapeworm).

Middle- a host in whose body the parasite is in the larval stage or reproduces asexually (humans for plasmodium malaria; pigs, wild boars for tapeworms).

reservoir- a host that is not obligatory in the life cycle of the parasite, but once in the organism the parasite does not die, even if it does not receive further development. Parasites accumulate in reservoir hosts. When the reservoir host is consumed by the definitive host, the parasite completes its development in its body. For example, in the human intestine, tapeworms can become parasites. Man is the main master for him. There are two intermediate hosts in the developmental cycle: the first is the cyclops crustacean, the second is many species of fish. But non-predatory fish can be eaten by predators, for example, pike. In this case, the helminth larvae do not die, but accumulate in the muscles of the pike, and it becomes the reservoir host.

This way,The host organism is a kind of habitat for the parasite.The doctrine of the host organism as a parasite habitat was fully developed by Academician E. N. Pavlovsky.The whole of all organisms living simultaneously in any organism is called parasitocenosis.

Classification of parasites

According to the degree of need for the species to live a parasitic lifestyle:

  • false parasitism- free-living individuals of a species accidentally enter the body of another species, where they remain viable and cause disruption in the normal life of the host. After a short parasitism in the host organism, the pseudoparasite dies or is released into the environment. For example, coprophilic amoeba can live in feces. When the stool is dry, it will come out. Coprophilic amoeba cysts can accidentally enter the human intestine. Cysts usually pass through the intestines and are excreted into the external environment with feces. In some cases, the amoeba in the human intestine emerges from a cyst and becomes a parasite for a short period of time, causing acute indigestion.
  • Facultative parasitismsuggests the possibility for species to live both free-living and parasitic modes. With this form of parasitism, a free-living species accidentally enters the body of another species, using it temporarily as a habitat and food source. Compared to pseudoparasites, facultative parasites spend a longer time in the host organism. An example of facultative parasitism is an amoeba that lives independently of the generaNaegleriaandAcanthamoeba. Negleria and Acanthamoeba live in water bodies that receive sewage. Entering the human body through the mouth or a cut on the skin, they can cause severe amoebic meningoencephalitis, sometimes fatal.
  • True (obligatory) parasitism.- the parasitic way of life is mandatory for at least one of the stages of development. True parasites are trypanosomes, leishmania, malarial plasmodia, pig and cattle 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's body are calledendoparasites. Accordingly, localization differentiates intracellular, tissue and cavity parasites. Endoparasites can affect any organ. There are intestinal parasites (tapeworms and roundworms, protozoa), liver parasites (flukes), lung parasites (pulmonary fluke), genitourinary system (schistosomes, Trichomonas) and other organs. Parasites can be localized in only one organ or infect multiple organs of the host.

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

  • Temporary parasiteThey are usually parasitic on the external integument of the host (ectoparasite). They are connected to the host organism only through the food chain (for example, hematophages), and their contact time with the host is much shorter than the period of free life.
  • Stationary parasitesspend in (on) the owner for a long time, sometimes their entire life. 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) andfixed(the parasite does not leave its host). Periodic parasitism is more common than permanent parasitism.

By specialtyParasites are divided into monospecific and polyspecific.

  • Parasites adapted to life in organisms of different host biological species are calledpolyspecific. A variant of polyspecificity is polyphagy - the ability of a blood-sucking parasite to feed on the blood of hosts of different species. For example, sexually mature stages of liver disease (Fasciola hepatica) parasites of various herbivores; many types of mosquitoes (familyCulicidae) 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 monospecies is monophagy - feeding on blood-sucking parasites at the expense of hosts of the same species. An example of monospecificity is the parasitization of human ticks of the speciesPediculus humanus. Once on the surface of the body of any other species, these ticks die. human Ascaris (Ascaris lumbricoides) is also a monospecific parasite. Once in the body of another host, they die before reaching puberty.

What parasites live in the human body

Human internal flora is an excellent environment for habitat and active reproduction of microorganisms belonging to the pathogenic group. The 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 harmful. In the course of their life, they can not only have a negative effect on the organs, but also to release toxic substances that poison all living things.

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

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

This microorganism parasitises the wall 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, loss of appetite, chattering teeth in 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 laying eggs.

These helminths live in the bodies of cats and dogs and enter the internal environment of humans through contact with these animals. This type of intestinal parasite can reach 3 cm in length and can be found in all internal organs and channels without exiting.

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


Parasite 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. Worms that live in the intestine are able to penetrate the blood vessels, through which they spread throughout the body through the bloodstream and settle in any organ.

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

The classification of parasites according to the type of helminths includes the trematode class, which consists of the following microorganisms:

  • Opisthorchis is a simple parasitic worm that often lives in the stomach, gall bladder, pancreas and liver, which leads to the development of gastritis, ulcers and pancreatitis. Guts in any such form did not interest him;
  • strongyloid - intestinal acne, is a worm up to 2 cm long. It affects the gastrointestinal tract. His life expectancy is not long, but at the same time, his activity successfully leads a person to asthma, gastrointestinal dysfunction, bronchitis, asthenia and other diseases.

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

These microorganisms consume large amounts of tissue and blood, often paralyzing the circulatory system.

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

The most common types of cestodes are:

  • pig tapeworm - grows up to 8 m long. At first, symptoms of invasion do not appear, but then the activity of the pig tapeworm leads to intestinal obstruction. It is also possible to develop asthenia;
  • cattle tapeworm - can grow up to 18 m long. It causes dangerous diseases for humans, including anemia, intestinal obstruction, allergies, gastrointestinal disorders and, as a result, the nervous system;
  • Tapeworm width - the length of this parasite reaches 8 m. One of the few parasites in humans that live in the small intestine. Causes anemia, asthenia, problems with the digestive tract and intestinal obstruction;
  • echinococcus - is considered the most dangerous tapeworm, an infection that in the first stage does not show any symptoms. However, the too rapid spread of helminths throughout the body leads to the formation of tumors.


Thinking about the types of parasites that exist 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, because it is its own special species of parasite 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 gets its name for its simple structure consisting of only one cell. However, it can cause various dangerous diseases in the human body.

The main types of parasitic protozoa:

  • Trichomonas. Although there is only one cell, they have a very complex structure. There are several types of this type of parasite, depending on the level of localization: mouth, intestine and vagina. The most common infection occurs with the presence of this organism in the reproductive system. Trichomonas often leads to prostatitis in men. Affects the brain and nervous system;
  • lamblia. Localized in the intestine. 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. Able to cause asthenia and indigestion, and also create intestinal obstruction;
  • toxoplasma. This parasite is very dangerous for pregnant women, because it can trigger 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.


Parasitic microorganisms of this type, such as ectoparasites, form a separate group of carriers of dangerous infections. This class is distinguished by the fact that its representatives are localized exclusively on the surface of human skin, but, nevertheless, they can infect it with dangerous diseases such as anthrax, typhoid, encephalitis, trypanosomiasis and others.

It is not difficult to recognize the appearance of parasites from this group, because, as a rule, they cause significant discomfort to their host. The main consequences of their bites include the appearance of allergic reactions, itching and burning.

To overcome 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. A very dangerous ectoparasite of an exotic species, which can be picked up during travel. The bite 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 done comprehensively and consult a doctor. However, the important thing is the correct diagnosis of infection with harmful microorganisms.

Usually, the symptoms that the human body is exposed to parasitic infection are as follows:

  • constipation - caused by intestinal obstruction related to the large size of the worm. In addition, helminths can block the flow of bile, causing painful discomfort in the lower abdomen;
  • frequent gas formation - usually caused by worms that have settled in the small intestine. This also includes a large bowel syndrome called;
  • diarrhea - liquefaction of stool caused by special substances secreted by some microorganisms. Loose stools that are too frequent may indicate an infection;
  • Allergic reactions - usually occur on waste products of microorganisms in a person. It is also possible the appearance of eczema and skin rashes;
  • joint and muscle pain discomfort. If these signs appear for no apparent reason, checking for the presence of parasites is mandatory. Some of them prefer to live exclusively in joint fluid and muscles, and pain is an immune response to the appearance of microorganisms;
  • weight jump, problems with appetite - associated with human poisoning by waste products of parasites and lack of glucose;
  • chronic fatigue syndrome, sleep disorders, anxiety and irritability. He says more often that the body's resources have been exhausted due to the strong 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, the treatment of 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 bodies of animals, humans, birds and fish and eat their hosts 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 - this includes giardia, amoeba dysentery, trypanosoma, etc.
  • Roundworms - roundworms and pinworms take root well in the human body
  • Flatworms - the human body is the best place where pig and cattle tapeworms, heartworms, etc. can live.
  • Ticks and fleas
  • Fleas and flies

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

Some individuals can generally live in cells and tissues, and from there it is almost impossible to remove them. It's about worms. With insects, the situation is a little easier, because 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 type and place 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 a flat ribbon. There is also the most harmless type of flatworm for humans - these are ciliary worms. But let's talk about dangerous parasites - worms and tapeworms - in more detail.

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

This type of worm is very long, and it always grows to its full potential. Tapeworms can grow up to 6. 5 meters in their lifetime. Representatives of tapeworms - tapeworms of cattle and pigs - can reach a length of up to 10 meters. Parasites live in the human intestine, which is in the thin part. The most dangerous type of tapeworm is echinococcus, which can affect the brain and lungs.

Weight loss with a normal appetite is the main sign of a tapeworm infection.


This type occurs mainly in children - kindergarten and primary school students. The most popular are roundworms, these are pinworms and roundworms, both of which tend to be parasitic in the intestine.

This type of parasitic worm does not attach to the walls of human organs in any way, because roundworms do not have any adaptations for this, however, they are not easy to remove. Pinworms tend to lay their eggs in the anal folds, thereby causing unbearable itching in 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 finger in his mouth, the infection occurs again.

And if those symptoms appear occasionally, then people in the rhythm of modern life simply do not notice them or do not care about them. And so pointless. There are many dire and irreparable consequences.

Experts recommend at least once a year to be tested for parasites - feces, blood. After all, timely detection of parasites in humans and efficient treatment will ensure a better quality of life.

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

  • Power decreases as the parasite multiplies and grows.
  • 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, because the body cannot protect itself from viruses.
  • In the course of their life, individual parasites secrete toxins that gradually accumulate in the human body. It is gradually poisoned, which is full of various infectious and even malignant diseases.


Prevention is an important part of pest control. It was said above what parasites are in the human body. For worms and protozoa, modern medicine offers a wide 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 worried about any symptoms. After conducting the necessary tests, the doctor himself will prescribe the right medicine, based on what parasites live in the human body.

After all, each drug acts on a specific type of parasitism; unfortunately, nothing is universal yet. And it is a specialist who will help you choose the medicine that is relevant in this case, fighting a certain type of parasite in a person.