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 are helminths, 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 vandelia), 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, not genetically related to it and that 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 damage. There are plant and animal parasites in nature, depending on the type of host. During the functioning of this lifestyle, the parasite and host system works constantly. The task of the first: to live by 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 forms, which under certain conditions begin to exist at the expense of another organism (facultative parasites).
3. Based on the timing 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, digestive system disorders, signs of damage to various internal organs).

Virus

Viruses are intracellular parasites of a protein genetic structure. Due 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, cause problems in various human organs.
2. Rhinovirus. Causative agents of ARVI.
3. Influenza, rabies and tick-borne encephalitis viruses.
4. Papillomavirus.

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

Viruses, entering the target cell, subordinate its processes to themselves, integrate into the genetic material or localize in the cytoplasm, then replicate (multiply). Hence, cell death occurs due to lysis, apoptosis, or distortion of the membrane structure. Some representatives (papillomavirus, Epstein-Barr virus) are capable of provoking the degeneration of cells into malignant ones.

How Viruses Get Inside:

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. Through 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 get infected with rickettsiae through the bites of ticks, fleas, lice.

Other intracellular chlamydial parasites cause one of the most common STDs (chlamydia) and cause severe eye inflammation, pneumonia in newborns and enteritis.

Dangerous bacteria include:

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

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 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), localized on various mucous membranes with a weakened immune system. Fungi of the genus Candida live in the body of any healthy person and bring tangible harm only 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 outer integument:

1. Keratomycosis. The 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, scab).
3. Deep mycoses. Damage to the 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. Which parasitic protozoa of a person are isolated depending on the systematic location?

1. Some types of amoebas are optional parasites. The most famous is the dysentery amoeba, 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 with them is dirty water. Acanthamoeba keratitis is a rare eye disease called Acanthamoeba keratitis, which has become more common due to the increased 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 includes only obligate parasites (Toxoplasma, Plasmodium malaria, Cryptosporidium, Coccidia, sarcocysts). Sporozoal 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 protozoal infections (protozoa). What parasites live in the human nervous system among protozoa? For example, the causative agents of toxoplasmosis and cerebral malaria. Among amoebas, 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 some species migrate or penetrate (rishta, Gnathostoma spinigerum larvae and hookworms, schistosomes) into the subcutaneous layer. Worms is the collective colloquial name for all worms that cause helminth infestations (helminthiasis).

Common diseases caused by flatworms

Group of trematodes (digenetic flukes):

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

The life cycle of the fluke group parasite is complex, including several larval stages and gastropods as intermediate carriers. Flukes are animal parasites of vertebrates, which act as temporary and permanent hosts. Individual larval stages can develop without fertilization. Flukes devices for fixing and feeding 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 together with the fertilized eggs. The stages of the life cycle of the tapeworm necessarily include the finna (bladder worm), which is formed in a temporary owner. The permanent host swallows the Finnish, which develops into a tapered (adult) form. The structural features of the tapeworm are the absence of a digestive system and the absorption of nutrients by the entire surface.

Most common:

1. Bovine tapeworm (disarmed tapeworm) causes tapeworm disease. Infection occurs through the meat of livestock, the muscles of which are contained by the Finns, formed in the body after the animals swallowed the eggs with food.
2. Pig tapeworm (tapeworm armed) is the causative agent of cysticercosis (Finn stage) and teniasis (adult). In addition to the suckers, the helminth is equipped with a rim of hooks. A person can simultaneously perform the function of intermediate and permanent owner.
3. Wide tapeworm causes diphyllobothriasis. Intermediate hosts are copepods and fish. A person can become infected with insufficiently salted caviar and poorly cooked or fried freshwater fish.

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

nematodes

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

1. Ascaris. Ascariasis includes migratory (larval) and intestinal (adult) stages. The larva penetrates the wall of the small intestine, moves into the lungs, bypassing the liver and heart, subsequently passing through the moulting stages. 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 areas of the small and large intestine, 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 fluids and blood.
4. Trichinella causes a dangerous trichinosis disease. 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. Mostly they get into the striated muscles, they can get into the eyes, causing pain and swelling of the face, into the lungs, leading to a cough. Until now, no cure has been invented for a complete cure.
5. Toksokara. Distinguish between larval (occurs more often) and imaginal (intestinal) toxocariasis. Invasion is characterized by the severity of allergic reactions. The larvae spread throughout the body, penetrating the tissues, encapsulating and forming granulomas.
6. Hookworm is most 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, strongyloidosis, can be asymptomatic for decades. With reduced immunity, carriers of the worm are at a 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 layer and when the host is in the water, they expel the larvae through the skin. The temporary host is a crayfish.

The peculiarities of the habitat of parasites influence the way they enter the body: contact with contaminated water or land, with carriers of larval stages that inhabit them. Many representatives of nematodes have no intermediate hosts and belong to geohelminths. Infection with them occurs mainly through contaminated water, unwashed hands, fruits or vegetables, as well as through the consumption of bushmeat.

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 concentrations along with other signs of infection indicate the presence of a worm and a host of pathogenic protozoa in the body. How are helminthiases treated? Medicines are used to relieve symptoms and specific treatment. An anti-allergic (desensitizing) and detoxifying therapy is used. Basically, drugs are administered by infusion (using a dropper), sometimes injections are used:

1. A drug that replaces plasma and removes the effects of toxins.
2. Isotonic glucose solution and saline.
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. Medicines for heart failure and edema.

There is evidence that some parasitic worms, such as pygmy tapeworms, can cause cancer. The stem cells of the larvae can degenerate into cancer cells. Parasites can indirectly cause cancer by weakening the immune system. Interesting data were obtained in the study of the effect of flukes on the liver. As a result of exposure to waste flukes, normal cells can turn into cancerous cells. Parasites are mainly localized in the digestive system, but their larvae are able to penetrate various internal organs. For example, in the kidneys (echinococcosis, schistosomiasis), heart muscle (cysticercosis, hookworm disease), liver (echinococcosis). Parasitic worms in humans often affect the nervous system. Known cysticercosis, echinococcosis, alveococcosis and cerebral schistosomiasis.

Arthropods

The order of insects includes well-known ectoparasites such as fleas, bed bugs, blood-sucking diptera. Unlike lice, these are temporary parasites, that is, they live erratically with the help of the host. Arthropod parasites in the order arachnids include the well-known scabies mite. Mating of male and female 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 arachnids, including the most famous representative of the taiga tick, a carrier of dangerous infections (tick-borne encephalitis, Lyme disease). Among the blood-sucking dipters are: non-malarial and antimalarial 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, particularly horseflies, deposit larvae under human skin, causing myiasis. The larvae are able to penetrate the body.