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 bacteria, viruses, protozoa, microscopic fungi, helminths (parasitic worms), and individual arthropods. These organisms not only consume nutrients absorbed by the host, but also poison it with the products of their vital activity. In accordance with the canons of modern medicine, the term "parasite" does not apply to prenuclear (prokaryotic) organisms: bacteria and viruses. It characterizes protozoa, fungi, worms, arthropods that live in the body of the host, subsisting exclusively on it.
Microparasites
Human and animal organisms are fertile habitats for microscopic fungi as well as protozoa. Indistinguishable 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 the tropics, as well as in temperate latitudes. About 50 species of protozoa parasitize human organs and tissues. They can be infected through sexual contact, food or insect bites.
Giardiasis is very common. Up to 40% of children and 10% of adults have this pathology. The lamblia's favorite habitat is the small intestine. The disease may be accompanied by digestive disorders, allergic reactions, although it is often asymptomatic. The pathogen is transmitted through the digestive tract - with unboiled water and contaminated food.
According to various sources, 30 to 50% of the world's population is infected with toxoplasmosis. Its pathogen often lives in the host without any clinical manifestations. Toxoplasma poses the greatest danger to pregnant women: it causes intrauterine fetal death or severe malformations. Infection occurs through contact with domestic mammals (cats, rabbits, rodents) and consumption of raw meat.
The most common sexually transmitted infection is protozoan. This is trichomoniasis. More than 150 million people are infected worldwide each year. The 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, protozoa affect the prostate gland, seminal vesicles, and in severe cases lead to prostatitis, although more often the infection is asymptomatic.
Diseases such as malaria, leishmaniasis, Chagas' disease and sleeping sickness are widely known in the tropics. Their causes are plasmodia, leishmaniasis and trypanosomes, respectively. The parasites are carried by blood-sucking insects: mosquitoes, tsetse flies, triatomic bugs. By biting sick animals or people, they acquire and spread the causes of these diseases.
Parasitic fungi
It is known that about 100 species of mushrooms are quite dangerous to humans. Their optimal habitat is the warm and humid areas of the body, such as 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: trichophytosis and pityriasis versicolor, lesions of the legs, 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;
- mucosa;
- aspergillosis.
These pathologies are characterized by inflammation of all parts of the airways without exception, otitis media and various allergic reactions. In severe cases, parasitic fungi cause pneumonia as well as bronchial asthma. People with weakened immunity and chronic diseases are most susceptible to fungal infections.
Helminths
The favorite habitat of parasitic worms is the digestive tract of humans and animals, in which they feed on the digestive food, bile and blood of the host. All helminths belong to the following classes:
- roundworms (nematodes);
- flatworms (tapeworms and flukes).
Flatworm
Eggs and larvae of trematodes (flat flukes) most often enter the human body with raw water, unwashed greens, insufficiently heat-treated meat and fish. Here's how:
- liver;
- Chinese
- giant;
- lanceolate flukes;
- feline methyl.
Sometimes a person becomes infected through direct contact: the larvae of tropical parasites of schistosomes pierce the skin of people swimming in fresh water, then enter the bloodstream in which they live and feed on red blood cells.
Most trematodes affect the liver, gallbladder and ducts of these organs, causing diseases - trematodes. The living environment for pulmonary methyl is the muscles, subcutaneous adipose tissue, brain, but above all the lungs. The disease caused by this helminth is called paragonimiasis. The small trematode metagony lives in the small intestine, leading to metagonymosis.
Butterflies are small in size - their flat leaf-shaped body does not exceed 10 cm - the consequences of their stay in the body of animals and humans are fatal. Long-term parasitism of these helminths can lead to cancer, cirrhosis and gallstone disease.
Unlike trematodes, the body of tapeworms (cestodes) can reach tens of meters in length. The main route of infection with cestodes is food. These helminths enter the human body with unprocessed meat and fish. The main environment for the development of cestodes is the small intestine, in which adult worms live, while the larval forms live in the parenchymal organs (liver, lungs, spleen).
Of all the tapeworms, the most common are:
- bull tapeworm;
- echinococcus;
- wide bar;
- swine tapeworm;
- alveococcus.
Round parasitic worms
Diseases caused by parasitic roundworms - nematodes - rank first among all helminthiasis in frequency of development. Most adult parasites are home to the intestines, but at certain stages of their lives they can migrate to the muscles, lungs, heart and pharynx. The following nematodes predominate in the human population:
- blades;
- roundworm;
- toxocara;
- Trichinella;
- hookworms;
- Strong.
The eggs and larvae of roundworms enter the human body through food and water. Nematodes such as hookworms and strongylids invade the host's body on their own. These helminths are found mainly in the tropics.
The ubiquitous nematodes are pinworms, roundworms and toxocara. The former most often affect children, causing enterobiosis - the most common helminthiasis. Dogs are carriers of Toxocara, although these nematodes can infect humans. Roundworms live in humans and are not dangerous to most animals except pigs.
Arthropod parasites
Cestodes, trematodes 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 causes of demodicosis and scabies. These parasites are dangerous because they can carry pathogenic bacteria and rickettsiae, which cause Volyn fever, typhoid fever and recurrent fever.
Lice drink human blood and parasitic mites live on human skin. The itching 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 evolving rapidly, living standards are constantly rising, and today it seems to many that parasitic diseases are part of the inhabitants of third world countries. However, population migration leads to the spread of such pathologies outside natural foci. In this regard, it is important to remember the basic hygiene rules, compliance with which will help avoid infection.