What are parasites: types and classification

Knowing the routes of entry of parasites into the body, it is possible to take preventive measures in contact with possible sources of infection. What helminths are, as intestinal parasites, is known to many. However, ordinary man is less aware of the species that live in the circulatory system, subcutaneous lymph, muscles, brain, and internal organs.

All types of parasites in the human body are classified into representatives: protozoa, flat and round worms, arthropods and their larvae.Viruses, pathogenic bacteria and fungi can be classified as parasites, but they are classified in a separate group. Infectious diseases are divided into: viral, fungal, bacterial and parasitic. The classification of human parasites includes - a unique species of fish (common vandellia), capable of entering the human urethra (random host).

Parasitism and its types

Who are the parasites? They are organisms living at the expense of another individual, not genetically linked to him and entering into antagonistic relationships, that is to say interfering with life. The concept of parasitism should not be extrapolated to microorganisms that live inside the body without causing special damage to it. In nature, there are plant and animal parasites, depending on the type of host. During the operation of this lifestyle, the parasitic and host system is constantly working. The task of the first: to live on the second, without killing it for a long time.

Classification of parasites by type:

1. Localization sites: external and internal parasites (exo- and endoparasites).
2. By way of life: constantly parasitic (obligatory) and free forms, which under certain conditions begin to exist at the expense of another organism (optional parasites).
3. By the moment of contact with the host: temporary and permanent parasites (stationary and periodic).

In the food chain, animal parasites are generally second or third order consumers, as they feed on herbivores or carnivores. The way the parasite feeds deprives the host of nutrients and / or leads to the destruction of cells and tissues. Host antagonism often occurs because dangerous inhabitants release toxic metabolic products. This leads to certain symptoms (allergies, disorders of the digestive system, signs of damage to various internal organs).

Virus

Viruses are intracellular parasites with a protein genetic structure. Thanks to the materials of the cell, they reproduce. The virus is an obligate parasite.

According to the classification, depending on the type of genetic material, viruses containing RNA and DNA are isolated. The intracellular agents of the first group include:

1. Enterovirus. They multiply in the digestive tract, causing problems in various human organs.
2. Rhinovirus. Agents responsible for ARVI.
3. Influenza, rabies and tick-borne encephalitis viruses.
4. Papillomavirus.

The second group includes: adenoviruses (cause acute respiratory infections), herpes and pathogens of smallpox.

Viruses, entering the target cell, subordinate its processes to themselves, become part of the genetic material or localize in the cytoplasm, and then replicate (multiply). Then cell death occurs as a result of lysis, apoptosis, or distortion of the membrane structure. Some representatives (papillomavirus, Epstein-Barr virus) are able to provoke the degeneration of cells into malignant cells.

How viruses get inside:

1. Airborne.
2. Through the gastrointestinal tract by drinking water and eating food.
3. Through the skin and external mucous membranes, such as the conjunctiva of the eye.
4. Using arthropod vectors (insects, ticks).
5. Following the use of non-sterile medical devices (syringes, pipettes).

Each virus is adapted to a specific cell, distinguishes the target with the help of receptors.

Bacteria

Among bacteria, rickettsiae, intracellular parasites, occupy a special position. These are the most primitive representatives that resemble viruses. In humans, these microorganisms cause: typhus, tick-borne rickettsiosis, Rocky Mountain spotted fever. People get infected with rickettsiae through the bites of ticks, fleas and lice.

Other intracellular parasites of chlamydia cause one of the most common venereal diseases (chlamydia) and cause severe eye inflammation, pneumonia in infants and enteritis.

Dangerous bacteria include:

1. Salmonella is the causative agent of typhoid fever.
2. Staff of Tetanus.
3. A pale spirochete that causes syphilis due to difficult diagnosis of the disease, resulting in a delay in treatment.
4. Pneumococci, which can cause pneumonia and, less commonly, bacterial meningitis.
5. Tuberculosis bacillus, which may not manifest itself for a long time, then turn into an open form.
6. Escherichia coli due to its ability to develop resistance to antibiotics. Causes gastroenteritis, rarely meningitis and urinary tract infection.

External parasites such as Staphylococcus aureus are known to cause a wide range of skin infections. The most dangerous consequences of its activity: pneumonia, meningitis, osteomyelitis, endocarditis, severe shock due to exposure to bacterial toxins and sepsis (in everyday life we speak of blood poisoning).

Mushrooms

Pathogenic fungi - human parasites are better protected from the effects of drugs than bacteria. The most common fungal disease is candidiasis (thrush), localized on various mucous membranes with a weakened immune system. Fungi of the genus Candida live in the body of every healthy person and only cause tangible damage if the protective function fails. Conditionally pathogenic bacteria and fungi are a limiting group of microorganisms between the non-pathogenic and pathogenic categories. Therefore, as a rule, they are not classified as pests.

Pathogenic micellial fungi are human parasites that often cause diseases of the outer skin:

1. Keratomycosis. Reproduction of fungi occurs in the keratinized area of the epidermis or on the cuticles of the hair (trichosporia nodosum, versicolor versicolor).
2. Dermatophytosis. Pathogens affect not only the epidermis, but also the dermis, nails and hair (ringworm, scabies).
3. Deep yeast infection. Damage to the skin and surrounding tissues, as well as to internal organs. These include histoplasmosis - a serious systemic fungal disease, and aspergillosis - damage to the mucous membranes and skin caused by Aspergillus.

Common sources of bacterial and fungal infections are sick people, animals, soil, dirty water and food.

Protozoa

Protozoa are another single-celled parasite along with bacteria and fungi. Which protozoan parasites of a person are isolated based on systematic position?

1. Some types of amoeba are facultative parasites. The best known is dysentery amoeba, which enters the human body in the form of a cyst (form at rest). The pathogen enters the large intestine (luminal form), then enters the mucous membrane and affects various internal organs with the bloodstream. Amoeba are aquatic organisms, so their main source of infection is dirty water. Acanthamoeba keratitis is a rare eye disease called acanthamoeba keratitis, which has become more common due to the increasing popularity of contact lenses.
2. Flagellates (Leishmania, Giardia, Trichomonas). Trichomoniasis is the most common disease of the genitourinary system, dangerous for its complications (infertility, prostatitis, premature birth, etc. ).
3. Apicomplexes (Sporozoa). With the exception of colpodellids, the group only includes obligate parasites (Toxoplasma, Plasmodium malaria, Cryptosporidium, Coccidia, sarcocysts). Sporozoan cysts enter the body after being bitten by insects, eating infected animals, or drinking water.
4. Ciliates. For humans, balantidia is dangerous, causing diarrhea and ulcers in the intestinal wall due to activity in the large intestine. Ciliates are the largest single-celled pathogenic organisms.

The simplest human parasites cause protozoan infections (protozoa). Which parasites live in the human nervous system among the protozoa? For example, the causative agents of toxoplasmosis and cerebral malaria. Among amoebae, the facultative parasite Neglerius Fowler is capable of infecting the nervous system.

Multicellular

Multicellular parasites include tapeworms, roundworms, arachnids and insects. The former, as a rule, settle inside a person (in various internal systems and organs), and some species migrate or penetrate (rishta, larvae of Gnathostoma spinigerum and hookworms, schistosomes) in the sub- layercutaneous. Worms is the collective household name for all the worms that cause helminthic infestations (helminthiasis).

Common diseases caused by tapeworms

Group of trematodes (digenetic fluids):

1. Opisthorchiasis. Causative agents: types of liver fluke, for example, felines and Siberian fluke. Infection occurs as a result of eating infected, poorly thermally processed river fish.
2. Fasciolosis. Caused by liver and giant fluke. Infection occurs through consumption of contaminated water or coastal grass.
3. Schistosomiasis. The causative agents of schistosomes (the blood fluke, in particular) live mainly in hot climates. They penetrate the skin on contact with water.
4. Paragonimosis. The cause of the disease is lung fluke, which is found in hot climates. A crab or freshwater crab that is thermally infected with a worm and improperly treated is dangerous.

The life cycle of the trematode group parasite is complex, comprising several larval stages and gastropods as intermediate carriers. Moats are animal parasites of vertebrates, acting as temporary and permanent hosts. Individual larval stages can develop without fertilization. The devices for fixing and feeding the moats inside the host are suction cups.

Tapeworms are obligate parasites of the human small intestine. Their body is made up of segments (proglottids), which periodically break off and come out with the fertilized eggs. The stages of the life cycle of tapeworms necessarily include finna (vesicular worm), which is formed in a temporary owner. The permanent host swallows the Finn, which develops into a tapering (adult) shape. The structural features of tapeworms are the absence of a digestive system and the absorption of nutrients through the entire surface.

Most common:

1. Bovine tapeworm (unarmed tapeworm) causes teniarinhoses disease. Infection occurs through the meat of cattle, the muscles of which are contained by the Finns, formed in the body after the animals swallow eggs with food.
2. Pork tapeworm (armed tapeworm) is the causative agent of cysticercosis (Finn stage) and tapeworm (adult). In addition to the suction cups, the helminth is equipped with a rim of hooks. A person can simultaneously perform the function of intermediate and permanent owner.
3. The broad tapeworm causes diphyllobothriasis. Intermediate hosts are copepods and fish. A person can be infected with insufficiently salted caviar and undercooked or fried freshwater fish.

Parasites feed on blood and tissue (fluke) or digested food (tapeworm).

Roundworms

What types of parasites common in humans are roundworms (nematodes)?

1. Ascaris. Ascariosis includes the migratory (larva) and intestinal (adult) stages. The larva penetrates the wall of the small intestine, moves to the lungs, bypassing the liver and the heart, successively passing through the stages of molting. It enters the oral cavity, is swallowed again and becomes an adult in the small intestine.
2. pinworms. The causative agent of enterobiosis feeds in the final and initial areas of the small and large intestines, multiplies in the ileum. Females lay eggs in the anal folds, causing severe itching.
3. Vlasoglav is the cause of trichocephalosis. These parasites in the human body invade the mucous membrane of the initial section of the large intestine and feed on tissue fluid and blood.
4. Trichinella causes a dangerous disease of trichinosis. In severe cases, the nervous system is damaged. They are real killers, the larvae of which penetrate the wall of the small intestine and are transported throughout the body. Most of the time they get into the striated muscles, they can get into the eyes, causing pain and swelling in the face, into the lungs, causing a cough. So far, no remedy has been invented for a complete cure.
5. Toksokara. Distinguish between larval toxocarosis (occurs more often) and imaginal toxocarosis (intestinal). The invasion is characterized by the severity of the allergic reactions. The larvae spread throughout the body, enter the tissues, encapsulate and form granulomas.
Hookworm
6. is more common in the tropics and subtropics. With hookworm infection, the worms inside the intestine secrete proteolytic enzymes that destroy the walls and reduce blood clotting. Parasites inside a person appear as a result of the introduction of larvae through the skin from polluted water.
7. Escherichia coli and related species are tropical parasites. The disease they cause, strongyliasis, can be asymptomatic for decades. With reduced immunity, carriers of the worm are at high risk of death (60-85%).
8. Rishta is a subtropical helminth that causes dracunculiasis. The larvae enter the intestinal wall. The females reach the subcutaneous layer and when the host is in the water, they expel the larvae through the skin. The temporary host is a copepod crayfish.

The peculiarities of the habitat of the parasites affect their routes of entry into the organism: contact with water or contaminated soil, with carriers of larval stages which inhabit them. Many representatives of roundworms do not have intermediate hosts and belong to soil-transmitted helminths. Their infection occurs mainly through contaminated water, unwashed hands, fruits or vegetables, as well as through the consumption of meat from wild animals.

Treatment and disastrous consequences of helminthiasis

A blood test is an important way to diagnose helminthiasis. Eosinophils (a type of white blood cell) found in high concentration along with other signs of infection indicate the presence of a worm and a number of pathogenic protozoa in the body. How are helminthiasis treated? Medicines are used to relieve symptoms and specific treatment. Antiallergic (desensitizing) and detox therapy is used. Basically, drugs are given by infusion (using a dropper), sometimes injections are used:

1. A drug which replaces the plasma and suppresses the effects of toxins.
2. Isotonic glucose solution and saline solution.
3. Vitamins C and B6.
4. Sodium bicarbonate (soda), calcium chloride or gluconate.
5. Preparations used at elevated temperatures.
6. Hormonal drugs are used in difficult situations (hepatitis or allergic myocarditis). The potassium intake is combined with them.
7. Drugs for heart failure and edema.

Certain parasitic worms, such as the pygmy tapeworm, have been shown to cause cancer. Stem cells in larvae can degenerate into cancer cells. Parasites can indirectly cause cancer by weakening the immune system. Interesting data has been obtained in the study of the effect of trematodes on the liver. Due to exposure to used fluke, ordinary cells can turn into cancer cells. Parasites are mainly localized in the digestive system, but their larvae are able to enter various internal organs. For example, in the kidneys (echinococcosis, schistosomiasis), heart muscle (cysticercosis, hookworm), liver (echinococcosis). Parasitic worms in humans often affect the nervous system. Known cysticercosis, echinococcosis, alveococcosis and schistosomiasis of the brain.

Arthropods

The order of insects includes ectoparasiteswell-known such as fleas, bedbugs, blood-sucking Diptera. Unlike lice, they are temporary parasites, that is, they live inconstantly with the help of the host. Arthropod parasites of the order Arachnids include the well-known scab mite. Mating of male and female occurs on the surface of the epithelium. The parasites present in the human body then lay their eggs in the keratin layer of the skin causing severe itching. Many people know what ixodid ticks are. These are arthropod parasites of the arachnid order, the most famous representative of which is the taiga tick - a carrier of dangerous infections (tick-borne encephalitis, Lyme disease). Among the blood-sucking Diptera are: non-malarial and malarial mosquitoes, mosquitoes, midges, biting midges, horseflies and real flies. These arthropod parasites can cause a strong allergic response and are also carriers of dangerous viral and bacterial infections. Some flies, especially horseflies, deposit larvae under human skin, causing myiasis. The larvae are able to enter the body.