Which parasites can live in the human body?

It is customary to call human parasites all organisms living at their expense. They are bacteria, fungi, worms. Human parasites are divided into internal and external. Helminths - a variety of parasitic worms are the most unpleasant and destructive of the body.

what helminths look like in the human body

Parasites and the human body

Creatures parasitizing the human body can be external or internal. External include:

  • Mosquitoes.
  • Leeches.
  • Lice.
  • Microorganisms responsible for scabies.

But there are many more creatures who prefer to settle inside the body. These include:

  • Bacteria.
  • The simplest.
  • Helminths.
  • Fungal.

The external and internal organization of the parasite belongs to the simplest. Since they do not need to evolve to survive, their organization is greatly simplified.

bacteria in the human body

There are many creatures that prefer to settle inside the body. For example, it can be bacteria.

They cannot survive without a host organism because they are unable to obtain their own food. But they all multiply, almost without exception, very quickly, especially under favorable conditions. Where they are not immediately taken.

They differ geographically. Some can be found everywhere, no climate is an obstacle for them. Others live exclusively in tropical countries, but on the human body they can easily be brought to any other. In the body, they also settle in different places.

The luminal parasites are satisfied with the hollow parts of the body, and the tissue parasites live in the tissues.

The development cycles of parasites, mainly helminths, are also varied. Some first grow in the soil (biohelminths) and then move to a living creature. Others must first develop in the body of any other living creature, but not in a person. Still others in an already adult state can be transferred to another or reinfect themselves.

It is a mistake to assume that infection can occur exclusively through dirty hands. The eggs of some helminths are viable outside the nutrient medium for six months and adhere well to animal hair. Eggs also survive in a dangerous environment for them - if you don't cook meat or fish properly, a whole brood of worms can settle inside you.

raw meat as a source of parasitic infestation

It is worth not cooking the meat properly, as a whole brood of worms can settle in you.

Human endoparasites

Parasites are divided into endoparasites and ectoparasites. Endoparasites - those who live indoors, ecto - outdoors. Endoparasites are able to settle in almost any internal organ and tissue in the body. They are divided according to location. Endoparasites are:

  • Endoparasites of internal organs connecting to the external environment.

They settle precisely in those organs which are linked to the external environment, and not the other way around: the parasitic organism does not choose to "breathe". These organs include the intestines, lungs, and the human urinary-reproductive system. They are parasitic amoeba, worms and flagellates.

  • Blood parasites.

They live in human blood. They can live in plasma, white blood cells, erythrocytes. These are trypanosomes, microfilariae or hemosporidia.

  • Tissue endoparasites.

These endoparasites that choose the tissues of the body as their place of residence. Muscle tissue, brain, cartilage, connective tissue. Even in nerve fibers, tissue endoparasitis can set in. These are Finnish tapeworms, trypanosomes, myxosporidia, trichinae and others.

endoparasites in the human brain

Endoparasites can choose the brain as their place of residence.

The definition of the type of parasite by the place of its localization is rather arbitrary. Many species are able to migrate through various internal organs and travel regularly through the host's body. The reproductive process can take place in one place, and the organisms will directly exist and feed in another. The place where the parasitic creature settles and will be considered the place of its conditional localization.

Despite the simplification of many parasitic systems, their life cycle is quite complex.

Some species throughout their life must change several hosts, which may belong to different biological species. Others are able to survive within a single species, but they may require intermediate hosts. In one person they multiply, and in another they develop and mature. With such a complex life cycle, their sexual functions are significantly increased. In order to survive in the body, the parasites must multiply quickly and a lot.


There are three main types of helminths, also called worms. He:

  • Nematodes are round worms.
  • Cestodes, band-shaped endoparasites.
  • Trematodes, also known as a fluke.
soil as a source of human infection by parasites

Soil-transmitted helminths begin their existence in the earth's soil.

Additionally, they can be divided based on lifecycle length and the number of locations they pass through along the way. There are also three types:

Soil-transmitted helminths

"Geo" is the earth. These worms begin their existence in the earth's soil, only after the stage of maturation are they able to infect a person. They do not need intermediate hosts; the eggs enter the soil with human faeces. Until the larval stage, they develop exclusively during the hot season.

These worms include roundworms, intestinal eels, nekator, whipworms.

The larvae of these parasites can enter the human body through unwashed vegetables or through direct contact with the soil.


They are parasitic worms whose life stages pass through several hosts. There may be two or more intermediate hosts, depending on the type of worm. Some parasites change only one person. Others, before finally entering the human body, use the organisms of other biological beings to develop.

cat as the cause of human infection with parasites

You can get infected from pets or from contact with other people, as well as from eating half-raw meat. Biohelminths include bovine tapeworms, echinococcus, broad tapeworm, trichina and others.

Contagious worms

These worms do not need soil or intermediate hosts. They go through all stages of their life cycle in one, very comfortably located organism. The larvae are excreted directly from the human body, when in contact with household surfaces and other people, they spread freely.

Helminths can live in different organs and systems of the human body, periodically migrating from one part of the body to another.

The list of diseases caused by helminths is very long. It is possible to determine which parasites live in the body and which treatment can be started only after all the tests necessary to establish the type of tests have been passed.

Round worms

Roundworms, also known as nematodes, are the most common in the human environment. In total, there are over 24, 000 species of nematodes in the world.

roundworm of the human body

The most common human nematodes are roundworms.

They are called round because of their shape, which is revealed if you make a cross section. The most common human nematodes:

  • Ascaris.
  • Pinworms.
  • Trichina.
  • Vlasoglava.

The helminthic infestation, known as ascariasis, begins with direct contact with soil infested with worms or by eating unwashed fruits and vegetables. Parasites begin to develop in the intestines, then enter the human circulatory system, from where they make their way to various internal organs, making their way to the oral cavity. A person, without realizing it, re-swallows an already adult parasite. They feed on the remains of undigested food. Ascaris waste is extremely toxic. There is no vaccine against ascariasis; infection can only be prevented by observing the rules of personal hygiene.

Pinworm infection is called enterobiosis. These are small worms (5-10 mm) that attach themselves to the intestinal walls. They feed on blood and intestinal contents. They lay their eggs under the skin, coming out of the anus while the owner is sleeping. Due to the itching, a person scratches the anal area, the larvae get under the skin and on the hands, and can be easily transmitted to other people in the house or in public places. There are no painful symptoms in enterobiosis; it is extremely problematic to detect infection with pinworms at the initial stage.

Trichinella, they are also Trichina, are round worms which choose an animal or a person as owner.

human body trichinella

Trichinella is a parasitic worm that infects the human body, causing the dangerous helminthic disease trichinosis.

They start to grow in the striated muscle area of the body, and then they are redirected to the small intestine. In advanced cases of infection, there may be around 15, 000 Trichina eggs per kilogram of muscle tissue. These parasites are able to cause a fatal disease, named after its source - trichinosis.

Whipworms are so named because of their appearance. The anterior part of their small body is threadlike, with an esophagus located inside.

The rear part is wider, the rest of the internal organs of the parasite are located there. The whipworm can be up to 50mm long. It feeds on blood and tissue fluid. Trichocephalosis causes the disease.


There are around 3, 500 known species of tapeworms in the world, also called cestodes. These tapeworms have no digestive system and the illnesses they cause are called cestodoses.

The most common cestodoses:


The disease is caused by the larvae of the pork tapeworm, which get inside through contaminated food, dirty hands.

pork tapeworm larvae in human body

The disease affects the skin, bones, internal organs, brain, and spinal cord. Most often, the parasites are sent to the brain (in 60% of cases of infection). It is diagnosed on the basis of the appearance of rounded formations on the skin. The disease is treated; in the event of infection of the central nervous system, the prognosis may be unfavorable.


It is located in the liver, lungs and many other internal organs. Echinococcus larvae excite the disease. They can develop inside a person over the course of several years.

Infection occurs through contact with animals, picking berries and fruits, drinking contaminated water.

The course of the disease is not too noticeable, it can develop over the years and turns out to be detected only by chance.


Alveococcosis is caused by the larvae of the alveococcal worms. The disease is similar to echinococcosis, but is more serious. Affects the lungs and kidneys. Left untreated, the disease is very likely to be fatal due to the development of liver failure.

human kidney as the habitat of the alveococcal parasite

Alveococcosis most often affects the kidneys.


Teniarinhoz is caused by a bovine tapeworm. It parasitizes the tapeworm in the area of the human small intestine, develops over a period of 2, 5 to 4 months. The prognosis of treatment is often favorable. Parasites can get inside a person with infected or insufficiently heat-treated raw meat.

Tapeworms are very prolific. They have the lowest remaining sensitivity and no digestive system. Such parasites cannot develop without a host.

To Fluke

Moats are moats. They are flatworms, in the shape of a body resembling an oblong leaf of a tree.

Some species of trematodes can measure up to a meter and a half.

And they are most often found in the human body through fish or other seafood. About 7, 200 fluke species are known, of which 40 inhabit humans and cause trematodes, a serious disease caused by infection. .

The most common moats:

Liver fluke

Distributed worldwide, can exist in animals and humans. The biological cycle is complex, the parasite changes hosts.

hepatic druust of the human body

The most common fluke is the liver fluke.


Schistosome larvae can penetrate the skin or mucous membranes. The life cycle is complex, they feed on blood. A female is able to produce about 3000 eggs per day, the fertility of these parasitic worms is very high.

Other liver fluke

They cause opisthorchiasis, a helminthic disease that mainly spreads in the liver. They have a toxic effect on the human body.

The digestive system of fluke worms is well developed, and with it the reproductive and excretory system.

The rest of the systems are developing poorly. Trematodes feed on blood, skin epithelial cells and intestinal contents. They can live almost anywhere: from the liver to the conjunctival sacs of the eyes.

Other types of endoparasites

The rest of the internal parasites are a variety of bacteria that cause dangerous diseases, and with them the simplest microorganisms. The fungus that spreads inside the human body also belongs to the section of endoparasites.

Many beneficial and harmful microorganisms live in the human body. Some of them cause quite dangerous diseases that can lead to death. It is not always possible to immediately recognize the presence of parasitic creatures per se, but an early diagnosis of the infection gives a better chance of a complete recovery. If an invasion is suspected, it is recommended to undergo a full examination by a doctor promptly.