Human parasites can inhabit all organ systems. The vital activity of helminths can become a prerequisite for the development of cancer, and microscopic fungi and mites lead to allergies.
The human body can be inhabited by at least 300 parasitic species, including representatives of bacteria, viruses, protozoa, microscopic fungi, helminths (parasitic worms), individual arthropods. These organisms not only consume nutrients assimilated by the host, but also poison it with the products of their vital activity. In accordance with the canons of modern medicine, the concept of "parasite" does not apply to prenuclear organisms (prokaryotes): bacteria and viruses. It characterizes protozoa, fungi, worms, arthropods that live in the host's body, surviving exclusively on it.
Microparasites
Human and animal organisms are a fertile environment for the life of microscopic fungi and protozoa. Indiscernible to the naked eye, they cause damage to the skin and internal organs.
Parasitic protozoa
An infection caused by a protozoan is called a protozoan. Such diseases are widespread in tropical areas as well as in temperate latitudes. About 50 species of protozoa parasitize in human organs and tissues. They can become infected through sexual contact, food, or insect bites.
Giardiasis is widespread. Up to 40% of children and 10% of adults have this pathology. The preferred habitat for lamblia is the small intestine. The disease can be accompanied by digestive disorders, allergic reactions, although it is often asymptomatic. The pathogen is transmitted via food - with unboiled water and contaminated food.
According to various sources, 30 to 50% of the world population is infected with toxoplasmosis. Its pathogen often lives in the host's organism without any clinical manifestations. Toxoplasma represents the greatest danger for pregnant women: it causes fetal death within the uterus or severe malformations. Infection occurs through contact with domestic mammals (cats, rabbits, rodents) and the consumption of raw meat.
The most common sexually transmitted infection is the protozoan. This is trichomoniasis. More than 150 million people are infected each year worldwide. Manifestations of the disease are determined by which organs are affected. In women, Trichomonas lives in the vagina, causing inflammation, accompanied by urethritis. In men, the protozoan affects the prostate gland, seminal vesicles, in severe cases leading to prostatitis, although more often the infection is asymptomatic.
In tropical regions, diseases such as malaria, leishmaniasis, Chagas disease and sleeping sickness are widely known. Their etiological agents are plasmodia, leishmania and trypanosomes, respectively. Parasites are carried by blood-sucking insects: mosquitoes, tsetse flies, triatomous insects. By biting animals or sick people, they acquire and distribute the causative agents of these diseases.
Parasitic mushrooms
About 100 species of fungi are known to be quite dangerous to humans. Their optimal habitat is the warm and humid areas of the body, for example the interdigital spaces. However, these organisms can also infect the skin and other areas of the human body.
Fungi of the species Trichophyton, Microsporum, Epidermophyton cause dermatomycosis: ringworm and pityriasis versicolor, lesions of the feet, scalp, rarely mucous membranes. The causative agents of these diseases can be transmitted to humans from animals or sick people. In severe cases, bacterial infections join dermatomycosis.
Mold fungi and their spores are no less harmful to humans. They cause diseases like this:
- penicellosis;
- mucous;
- aspergillosis.
These pathologies are characterized by inflammation of all parts of the respiratory tract without exception, otitis media and various allergic reactions. In severe cases, parasitic fungi cause pneumonia and bronchial asthma. People with weakened immunity and chronic diseases are more susceptible to fungal infections.
Helminths
The favorite habitat of parasitic worms is the digestive tract of humans and animals, where they feed on the digested food, bile and blood of the host. All helminths belong to the following classes:
- nematodes (nematodes);
- flat worms (tapeworms and flukes).
Flat parasitic worms
The eggs and larvae of flukes (flat worms) very often enter the human body with untreated water, unwashed vegetables, insufficiently thermally treated meat and fish. Here's how:
- hepatic;
- Chinese
- giant;
- lanceolate flukes;
- cat fluke.
Sometimes a person becomes infected by direct contact: the larvae of the tropical parasites of schistosomes pierce the skin of people swimming in fresh water, then enter the bloodstream, where they live and feed on erythrocytes.
Most flukes affect the liver, gallbladder and ducts of these organs, causing disease - flukes. The environment for the life of a lung fluke is the muscles, the subcutaneous fatty tissue, the brain, but especially the lungs. The disease caused by this helminth is called paragonimiasis. The small trematode metagonium lives in the small intestine, leading to metagonimosis.
Flukes are small in size - their flat leaf-shaped body does not exceed 10 cm - however, the consequences of their stay in the body of animals and humans are fatal. Long-term parasitism of these helminths can lead to the development of cancer, cirrhosis and gallstones.
Unlike flukes, the body of tapeworms (tapeworms) can reach tens of meters in length. The main route of tapeworm infection is food. These helminths enter the human body with raw meat and fish. The main environment for the development of tapeworms is the small intestine, in which adult worms live, while the larval forms live in the parenchymal organs (liver, lungs, spleen).
Of all tapeworms, the following are the most common:
- bullish tapeworm;
- echinococcus;
- wide ribbon;
- pork tapeworm;
- alveococcus.
Round parasitic worms
Diseases caused by parasitic nematodes - nematodes - are the first among all helminthiases in terms of frequency of development. The habitat of most adult parasites is the intestine, but at some stages of their life they can migrate to the muscles, lungs, heart and pharynx. In the human population, the following nematodes prevail:
- pinworms;
- nematodes;
- toxocars;
- Trichinella;
- hookworms;
- Strongylids.
Roundworm eggs and larvae enter the human body through food and water. Roundworms such as hookworms and strongyles themselves invade the host's body. These helminths are mainly found in the tropics.
The ubiquitous nematodes are pinworms, roundworms and toxocara. The former most often affects children, causing enterobiasis, the most common helminthiasis. Dogs are carriers of Toxocara, although these nematodes can infect humans as well. Nematodes live in humans and are not dangerous to most animals, with the exception of pigs.
Arthropod parasites
Cestodes, flukes and parasitic nematodes are adapted to live in the internal organs of their hosts. In contrast, most parasitic arthropods live on the surface of the body. Most often, a person becomes infected with lice and mites, the causative agents of demodicosis and scabies. These parasites are dangerous because they can carry pathogenic bacteria and rickettsia that cause Volyn fever, typhus and relapsing fever.
Lice drink human blood, and parasitic mites live on human skin. The itch of scabies gnaws through the passages in it, demodex lives in the hair follicles and ducts of the sebaceous glands. The vital activity of these parasites leads to allergies, accompanied by rash, redness of the skin and itching.
The world we live in is developing rapidly, the standard of living is constantly increasing and today it seems to many that parasitic diseases are the fate of residents of third world countries. However, population migration leads to the spread of these diseases beyond natural outbreaks. In this regard, it is important to remember the basic rules of hygiene, observance of which will help to avoid infection.