What are parasites: types and classification.

Knowing the entry routes 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, 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 they are distinguished 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 vandellia), capable of penetrating the human urethra (random host).

Parasitism and its types

Who are the parasites? These are organisms that live at the expense of another individual, are not genetically related to him and enter into antagonistic relationships, that is, they interfere with life. The concept of parasitism should not be extrapolated to microorganisms that live inside the body without causing special harm. In nature, there are plant and animal parasites, depending on the type of host. During the functioning of this life form, the parasite and the host system work constantly. The task of the first: to live off 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 (obligate) and free-living forms, which under certain conditions begin to exist at the expense of another organism (facultative parasites).
3. According to the moment of contact with the host: temporary and permanent parasites (stationary and periodic).

In the food chain, animal parasites are usually 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, digestive system disorders, signs of damage to various internal organs).

Virus

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

According to the classification, according to the type of genetic material, viruses containing RNA and DNA are isolated. Intracellular agents of the first group include:

1. Enterovirus. They multiply in the digestive tract, cause problems in various human organs.
2. Rhinovirus. Causal agents of ARVI.
3. Tick-borne influenza, rabies, and encephalitis viruses.
4. Papillomavirus.

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

Viruses, which enter the target cell, subordinate their processes to themselves, integrate into the genetic material or localize themselves in the cytoplasm, then replicate (multiply). Then, cell death occurs as a result of lysis, apoptosis, or distortion of the membrane structure. Some representatives (papilloma virus, Epstein-Barr virus) are capable of causing the degeneration of cells into malignant ones.

How viruses get inside:

1. Airborne.
2. Through the gastrointestinal tract when drinking water and eating.
3. Through the skin and external mucous membranes, such as the conjunctiva of the eye.
4. By means of vector arthropods (insects, ticks).
5. As a result of the use of non-sterile medical devices (syringes, pipettes).

Each virus adapts 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 become infected with rickettsiae through tick, flea, and lice bites.

Other intracellular chlamydial parasites cause one of the most common venereal diseases (chlamydia), causing severe eye inflammation, infant pneumonia, 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 difficult diagnosis of the disease, leading to a delay in treatment.
4. Pneumococci, which can cause pneumonia and, less commonly, bacterial meningitis.
5. Tuberculosis bacillus, which may not manifest for a long time and then develop into 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 range of skin infections. The most dangerous consequences of its activity: pneumonia, meningitis, osteomyelitis, endocarditis, severe shock from 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 various mucous membranes with a weakened immune system. Fungi of the genus Candida live in the body of any healthy person and cause tangible harm only if the protective function fails. Conditionally pathogenic bacteria and fungi are a borderline group of microorganisms between the pathogenic and non-pathogenic categories. Therefore, as a general rule, they are not classified as parasites.

Pathogenic mycelial fungi are human parasites that often cause diseases of the outer 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, scab).
3. Deep mycoses. Damage to skin and nearby tissues, as well as internal organs. These include histoplasmosis, a severe 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.

Protozoa

Protozoa are another single-celled parasite along with bacteria and fungi. What protozoan parasites of a person are isolated according to the systematic position?

1. Some types of amoeba are facultative parasites. The most famous is the amoeba dysentery, which enters the human body in the form of a cyst (resting form). The pathogen enters the large intestine (luminal form), then penetrates the mucous membrane and affects various 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 prevalent due to the rise in popularity of contact lenses.
2. Flagellates (Leishmania, Giardia, Trichomonas). Trichomoniasis is the most common disease of the genitourinary system, dangerous due to its complications (infertility, prostatitis, premature birth, etc. ).
3. Apicomplexes (sporozoans). With the exception of colpodellids, the group includes only 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 as a result of activity in the large intestine. Ciliates are the largest pathogenic single-celled organisms.

The simplest human parasites cause infections by protozoa (protozosis). What parasites live in the human nervous system among 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 flatworms, roundworms, arachnids, and insects. The former, as a rule, settle inside a person (in various internal systems and organs), and certain species migrate or penetrate (rishta, Gnathostoma spinigerum larvae and hookworms, schistosomes) in the subcutaneous layer. Worms is the collective colloquial name for all worms that cause helminthic infestations (helminthiasis).

Common Diseases Caused by Flatworms

Group of trematodes (digenetic trematodes):

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

The life cycle of the fluke group parasite is complex and includes several larval and gastropod stages as intermediate carriers. Flukes are animal parasites of vertebrates, acting as temporary and permanent hosts. Individual larval stages can develop without fertilization. Flukes devices for fixing and feeding inside the host are dumb.

Tapeworms are obligate parasites of the human small intestine. Its body consists of segments (proglottids), which periodically break off and hatch along with the fertilized eggs. The life cycle stages of tapeworms necessarily include the finna (blister worm), which forms in a temporary owner. The permanent host swallows the Finn, who turns into a conical (adult) shape. 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 (disarmed tapeworm) causes teniarinhoses disease. The infection occurs through the meat of cattle, the muscles of which are contained in the Finns, which is formed in the body after the animals ingested eggs with food.
2. The pig tapeworm (armed tapeworm) is the causative agent of cysticercosis (Finnish stage) and tapeworm (adult). In addition to suction cups, the helminth is equipped with a hooked edge. One person can simultaneously perform the role of intermediate and permanent owner.
3. Broad tapeworm causes diphyllobothriasis. Intermediate hosts are copepods and fish. A person can become infected from insufficiently salty caviar and undercooked or fried freshwater fish.

Parasites feed on blood and tissues (flukes) or digested food (tapeworms).

Roundworms

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

1. Ascaris. Ascariasis includes migratory (larval) and intestinal (adult) stages. The larvae penetrate the wall of the small intestine, move to the lungs, bypassing the liver and heart, successively passing through the molting stages. It enters the oral cavity, is swallowed again, and becomes an adult in the small intestine.
2. Roundworm. The causative agent of enterobiasis feeds in the final and initial zones of the small and large intestines, multiplies in the ileum. Females lay eggs in the anal folds, causing intense itching.
3. Vlasoglav is the cause of whipworm. These parasites of 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. These are true killers, the larvae of which penetrate the wall of the small intestine and are carried throughout the body. They mostly penetrate the striated muscles, they can penetrate the eyes, causing pain and swelling of the face, up to the lungs, causing coughing. Until now, no cure has been invented for a full recovery.
5. Toksokara. Distinguish between larval (occurs more frequently) and imaginal (intestinal) toxocariasis. Invasion is characterized by the severity of allergic reactions. The larvae spread throughout the body, penetrate tissues, encapsulate, and form granulomas.
6. Hookworm is more common in the tropics and subtropics. With hookworm infection, the worms within 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 of contaminated water.
7. Escherichia coli and related species are tropical parasites. The disease they cause, strongyloidosis, can be asymptomatic for decades. With reduced immunity, carriers of the worm have a high risk of death (60-85%).
8. Rishta is a subtropical helminth that causes dracunculiasis. The larvae penetrate 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 crab.

The peculiarities of the parasites' habitat affect the way they enter the body: contact with contaminated water or soil, inhabiting carriers of larval stages. Many representatives of roundworms do not have intermediate hosts and belong to soil-transmitted helminths. Infection with them occurs mainly through contaminated water, unwashed hands, fruits or vegetables, as well as by eating wild animal meat.

Treatment and serious 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 helminthiases treated? Medications are used to relieve symptoms and specific treatment. Anti-allergic (desensitizing) and detoxifying therapy is used. Basically drugs are given by infusion (using a dropper), sometimes injections are used:

1. A drug that replaces plasma and eliminates 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 (with hepatitis or allergic myocarditis). Potassium intake is combined with them.
7. Medications for heart failure and edema.

There is evidence that certain parasitic worms, such as the pygmy tapeworm, can cause cancer. The stem cells of the larvae can degenerate into cancerous ones. Parasites can indirectly cause cancer by weakening the immune system. Interesting data were obtained in the study of the effect of trematodes affecting the liver. As a result of exposure to fluke debris, ordinary cells can turn into cancer cells. Parasites are mainly located in the digestive system, but their larvae can penetrate 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 such well-known ectoparasites as fleas, bed bugs, and blood-sucking diptera. Unlike lice, these are temporary parasites, that is, they live inconsistently with the help of the host. Arthropod parasites of the order Arachnids include the well-known scabies mite. The mating of males and females occurs on the surface of the epithelium. Parasites 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 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: non-malaria and malaria mosquitoes, mosquitoes, gnats, biting mosquitoes, horseflies and real flies. These arthropod parasites can provoke a strong allergic response and are also carriers of dangerous viral and bacterial infections. Some flies, particularly horseflies, deposit larvae under human skin, causing myiasis. The larvae can enter the body.