What are parasites: types and classification

Knowing the ways in which parasites enter the body, it is possible to take preventive measures in contact with possible sources of infection. What are helminths, like intestinal parasites, is known to many. However, the common 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 are differentiated into 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 vandelia), capable of penetrating the human urethra (random host).

Parasitism and its types

Who are the parasites? They are organisms that live at the expense of another individual, not genetically related to him and that enter into antagonistic relationships, that is, they interfere in life. The concept of parasitism should not be extrapolated to microorganisms that live inside the body without causing special damage. In nature, there are parasites from plants and animals, depending on the type of host. During the functioning of this way of life, the parasitic and host system works constantly. The task of the first: to live on the second, without killing him 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-living forms, which under certain conditions come into existence at the expense of another organism (optional parasites).
3. For the time 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 some symptoms (allergies, disorders of the digestive system, signs of damage to various internal organs).

Virus

Viruses are intracellular parasites of a genetic protein structure. Due to the materials of the cell, they reproduce. The virus is a mandatory 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 several human organs.
2. Rhinovirus. Agents causing ARVI.
3. Influenza virus, rabies and tick-borne encephalitis.
4. Papillomavirus.

The second group includes: adenovirus (causes acute respiratory infections), herpes and smallpox pathogens.

Viruses, entering the target cell, subordinate their processes to themselves, integrate with the genetic material or are located 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 capable of causing the degeneration of cells in malignant cells.

How viruses penetrate:

1. Airborne.
2. Through the gastrointestinal tract when drinking water and eating food.
3. Through the skin and external mucous membranes, such as the conjunctiva of the eye.
4. By means of arthropod vectors (insects, ticks).
5. As a result of using 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 are infected with rickettsiae through tick, flea and lice bites.

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

Dangerous bacteria include:

1. Salmonella is the causative agent of typhoid fever.
2. Tetanus rod.
3. A pale spirochete that causes syphilis due to a difficult diagnosis of the disease, which leads to a delay in treatment.
4. Pneumococcus, which can cause pneumonia and, less commonly, bacterial meningitis.
5. Tuberculosis bacillus, which may not appear for a long time and then become an open form.
6. Escherichia coli due to its ability to acquire resistance to antibiotics. It causes gastroenteritis, rarely meningitis and urinary tract infection.

External parasites, such as Staphylococcus aureus, are known to cause a wide variety 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 it is called blood poisoning).

Mushrooms

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

Pathogenic mycelial fungi are human parasites that often cause diseases of the external integument:

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

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

Protozoans

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

1. Some types of amoebae are optional parasites. The most famous is amoeba dysentery, which enters the human body in the form of a cyst (form at rest). The pathogen enters the large intestine (luminal form), then penetrates the mucous membrane and affects several internal organs with the bloodstream. Amoebas are aquatic organisms, so the main source of infection is dirty water. Acanthamoeba keratitis is a rare eye disease called acanthamoeba keratitis, which has become more frequent due to the increasing popularity of contact lenses.
2. Flagellates (Leishmania, Giardia, Trichomonas). Trichomoniasis is the most common disease of the genitourinary system, dangerous because of its complications (infertility, prostatitis, premature birth, etc. ).
3. Apicomplexes (sporozoa). With the exception of colpodelids, the group includes only mandatory 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 as a result of activity in the large intestine. Ciliates are the largest single-celled pathogenic organisms.

The simplest human parasites cause infections by protozoa (protozoa). What parasites live in the human nervous system among protozoa? For example, the agents that cause toxoplasmosis and cerebral malaria. Among amoebas, the optional parasite Neglerius Fowler is capable of infecting the nervous system.

Multicellular

Multicellular parasites include worms, roundworms, arachnids and insects. The former, as a rule, settle inside the person (in various systems and internal organs) and certain species migrate or penetrate (rishta, Gnathostoma spinigerum larvae and hookworms, schistosomes) into the subcutaneous layer. Worms is the collective colloquial name of all worms that cause helminth infestations (helminthiasis).

Common diseases caused by flatworms

Group of trematodes (digenetic worms):

1. Opisthorchiasis. Causing agents: types of liver worms, for example, feline and Siberian fasciole. The infection occurs as a result of eating infected river fish, poorly thermally processed.
2. Fascioliasis. Caused by giant and liver worms. The infection occurs through the consumption of contaminated water or coastal grass.
3. Schistosomiasis. The causative agents of schistosomes (blood worm, in particular) live mainly in hot climates. They penetrate the skin by contact with water.
4. Paragonimiasis. The cause of the disease is a pulmonary worm, found in hot climates. A thermally infected and poorly processed freshwater crab or crab is dangerous.

The parasite life cycle of the trematode group is complex, including several larval and gastropod stages as intermediate carriers. Worms are vertebrate animal parasites, acting as temporary and permanent hosts. The individual larval stages are able to develop without fertilization. Flukes devices for fixation and feeding inside the host are suckers.

Tapeworms are obligatory parasites of the human small intestine. Your body consists of segments (proglottids), which periodically break and come out along with the fertilized eggs. The stages of the tapeworm's life cycle necessarily include the finna (bubble worm), which forms in a temporary owner. The permanent host swallows Finn, which develops into a conical (adult) form. The structural characteristics of tapeworms are the absence of a digestive system and the absorption of nutrients throughout the surface.

Most common:

1. Bovine tapeworm (unarmed tapeworm) causes teniarosis disease. The infection occurs through the meat of the cattle, whose muscles are contained by the Finns, formed in the body after the animals swallowed the eggs with the food.
2. Swine tapeworm (armed tapeworm) is the causative agent of cysticercosis (Finn stage) and teniasis (adult). In addition to the suction cups, the helminths are equipped with a hook loop. A person can simultaneously play the role of intermediate and permanent owner.
3. The broad tapeworm causes diphyllobotriasis. The intermediate hosts are copepods and fish. A person can be infected through insufficiently salted caviar and undercooked or fried freshwater fish.

The parasites feed on blood and tissues (worms) or digested food (worms).

Roundworms

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

1. Ascaris. Ascariasis includes migratory (larval) and intestinal (adult) stages. The larva penetrates the wall of the small intestine, goes to the lungs, bypassing the liver and heart, passing successively through the stages of molting. It enters the oral cavity, is swallowed again and becomes an adult in the small intestine.
2. Pinworm. The causative agent of enterobiasis feeds in the final and initial zones of the small and large intestines and multiplies in the ileum. Females lay eggs in the anal folds, causing intense itching.
3. Vlasoglav is the cause of tricocephalus. 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 the dangerous disease of trichinosis. In severe cases, the nervous system is damaged. They are true killers, whose larvae penetrate the wall of the small intestine and are transported throughout the body. Mainly, they enter the striated muscles, can penetrate the eyes, causing pain and swelling of the face, to the lungs, causing coughing. So far, no cure has been devised for a complete recovery.
5. Toksokara. Distinguish between larval toxocariasis (occurs most often) and imaginal (intestinal) toxocariasis. The invasion is characterized by the severity of allergic reactions. The larvae spread throughout the body, penetrating the tissues, encapsulating and forming granulomas.
6. The hookworm is more common in the tropics and subtropics. In hookworm infection, the worms within the intestine secrete proteolytic enzymes that destroy the walls and reduce blood clotting. Parasites within a person appear as a result of the introduction of larvae through the skin of polluted water.
7. Escherichia coli and related species are tropical parasites. The disease they cause, strongyloidosis, can be asymptomatic for decades. With reduced immunity, worm carriers are at high risk of death (60-85%).
8. Rishta is a subtropical helminth that causes dracunculiasis. The larvae penetrate the intestinal wall. Females reach the subcutaneous tissue and, when the host is in the water, expel the larvae through the skin. The temporary host is a copepod crayfish.

The peculiarities of the parasites' habitat affect the ways in which they enter the body: contact with contaminated water or earth, with carriers of larval stages that inhabit them. Many roundworm representatives have no intermediate hosts and belong to geohelminths. Infection occurs mainly through contaminated water, unwashed hands, fruits or vegetables, as well as the consumption of meat from wild animals.

Treatment and dire consequences of helminthiasis

An important way to diagnose helminthiasis is a blood test. Eosinophils (a type of white blood cell) found in high concentration along with other signs of infection indicate the presence of a worm and several pathogenic protozoa in the body. How are helminthiasis treated? Medicines are used for symptom relief and specific treatment. Antiallergic (desensitizing) and detoxification therapy is used. Basically, medications are administered by infusion (using a dropper), injections are sometimes used:

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

There is evidence that certain parasitic worms, such as pygmy tapeworm, can cause cancer. Larvae stem cells can degenerate into cancer cells. Parasites can cause cancer indirectly by weakening the immune system. Interesting data were obtained in the study of the effect of trematodes that affect the liver. As a result of exposure to residual worms, ordinary cells can turn into cancer cells. The parasites are located mainly in the digestive system, but their larvae are able to penetrate various internal organs. For example, in the kidneys (echinococcosis, schistosomiasis), cardiac muscle (cysticercosis, hookworm), liver (echinococcosis). Parasitic worms in humans often affect the nervous system. Cysticercosis, echinococcosis, alveococcosis and cerebral schistosomiasis.

Arthropods

The order of insects includes ectoparasites well known as fleas, bedbugs, blood-sucking diptera. Unlike lice, they are temporary parasites, that is, they live unsteadily with the help of the host. Arthropod parasites of the order of arachnids include the well-known scabies mite. Mating of male and female occurs on the surface of the epithelium. The parasites in the human body lay their eggs in the keratin layer of the skin, causing intense itching. Many people know what ixodid ticks are. These are arthropod parasites of the order of arachnids, including the most famous representative of the taiga tick - a carrier of dangerous infections (tick-borne encephalitis, Lyme disease). Among the blood-sucking diptera, there are: malaria and non-malaria mosquitoes, mosquitoes, mosquitoes, biting mosquitoes, horseflies and real flies. These parasitic arthropods can cause a strong allergic response and are also carriers of dangerous viral and bacterial infections. Some flies, in particular flies, deposit larvae under human skin, causing myiasis. The larvae are able to penetrate the body.