The simplest parasite is an organism that is adapted to invade and live in the cells and tissues of other organisms. The simplest parasites cannot live in an open environment on their own like other protozoa, but must invade the body of another organism in order to receive protection and nourishment.
The simplest parasites and their varieties
The simplest organisms are eukaryotic systems that exist as structurally and functionally independent individual cells (including those species that are gregarious or forming colonies). Protozoa develop relatively complex subcellular traits (membranes and organelles) that allow them to survive in harsh environmental conditions. Most protozoa are microscopic organisms, and only a few of them grow large enough to be visible to the naked eye. As unicellular eukaryotes, they move to survive, feed, and reproduce.
There are some of the simplest parasites that cause problems. They are present in our food, soil and water, and can make us very sick if they ever get inside us.
Each different protozoan parasite can cause different diseases in our bodies. Some of them can cause serious diseases of the respiratory tract (air passage from the nose to the lungs) and the central nervous system (brain, cranial nerves and spinal cord), while others live in the intestines, causing symptoms such as diarrhea, and are notdeadly.
There are four types of protozoan parasites, which are classified according to how they move:
- sarcodes are a group of amoebas that move using pseudopods and contractions that change the shape of their cells;
- mastigophores move with the help of flagella;
- siliophores use cilia;
- sporozoans are immobile when they are at their mature stage.
Life Cycles of Protozoa Parasites
Most protozoa have enormous reproductive potential because they have a short generation time, undergo rapid sequential development, and produce large numbers of offspring asexually or sexually. These characteristics are responsible for many of the simplest infections, rapidly causing acute symptoms of the disease.
The developmental stages of protozoan parasites that occur within the host usually consist of feeding trophozoites and can be found intracellularly (within the host's cells) or extracellularly (in hollow organs, body fluids, or internodes between cells). Although trophozoites are ideal for their parasitic mode of existence, they are not very resistant to external environmental conditions and do not survive long outside of their hosts. To move from host to host, protozoan parasites use one of four main modes of transmission: direct, fecal-oral, transmissible, and from predator to prey.
Ways of transmission of protozoan parasites to humans
- Direct transmission of parasites through intimate contact with the body - sexually (for example, Trichomonas spake fungi, which cause trichomoniasis in humans).
- Fecal-oral transmission of ecologically stable stages of cysts - parasites pass in the feces of one host and are transmitted with food or water to another (for example, Entamoeba histolytica, Giardia duodenalis and Balantidium coli are all forms of fecal cysts that lead to amoebic dysentery, giardiasis and balantidiosis).
- Transmissible parasite transmission occurs when they are ingested by blood-sucking arthropods (insects or arachnids) and transferred to new hosts by a bite (for example, Trypanosoma brucei, transmitted by tsetse flies and causing sleeping sickness, and Plasmodium spp. haemosporidia, transmitted by mosquitoes and causing malaria).
- Transmission from predator to prey occurs when the simplest parasite gets stuck in the tissues of the prey (for example, a cow, goat, pig), and it is eaten by a predator (in our case, a person).
The simplest human parasites and the diseases they cause
Acanthamoeba. This parasite infects a person's eyes or brain and causes exogenous amoebiasis. He can live in any region of the world. People can get it when cleaning contact lenses with tap water.
BabesiaIt infects red blood cells and causes a disease called babesiosis. Different types of parasite live in different parts of the world. It is transmitted by ticks when bitten.
Balantidium (Balantidium coli). Lives in the intestinal mucosa, causes ciliated dysentery, also called balantidiosis.
Blastocystis (Blastocystis). This parasite infects the intestines of the host. It enters humans through ingested food contaminated with human or animal feces. The disease caused by this parasite is called blastocytosis.
Cryptosporidium (Cryptosporidium). Lives in the human intestine. Distributed throughout the world. It enters the human body through ingested food contaminated with human or animal feces.
Dysentery amoeba (Entamoeba histolytica). This simplest parasite causes intestinal amebiasis. Most often found in areas with high population density, poor sanitation and tropical regions. It is transmitted by the fecal-oral route.
Giardia lamblia. Lives in the lumen of the small intestine. If people consume food or water contaminated with faeces, dormant Giardia cysts can infect the body, causing intestinal giardiasis. It is especially dangerous for children and requires mandatory adherence to the treatment regimen.
Isospore (Isospora belli). Affects the epithelial cells of the small intestine. Distributed all over the world. It is transmitted by the fecal-oral route and is the causative agent of isosporia.
Leishmania. Parasitizes the skin and internal organs of a person. It exists all over the world in various forms. Transmitted by some types of mosquitoes when bitten.
Negleria (Naegleria fowleri). Causes primary amoebic meningoencephalitis, as it lives in the human brain. Infection occurs through contaminated soil, swimming pools and contaminated water.
Plasmodium (Plasmodium falciparum, P. vivax, P. ovale, P. malariae). Parasites enter red blood cells and cause malaria. They exist in tropical regions where Anopheles, also known as the anopheles mosquito, are carried.
Rhinosporidium seeberi. It multiplies in the nose and nasopharynx, growing there in the form of spores. It exists in India and Sri Lanka. People who swim in public waters can become infected with the parasite when the nasal mucosa is in contact with contaminated material.
Toxoplasma (Toxoplasma gondii). Affects the liver, heart, eyes and brain. A widespread parasite throughout the world. People can become infected after eating raw or undercooked pork, lamb, goat, or milk. May also exist in contaminated food or soil due to cat feces. The disease caused by this parasite is called toxoplasmosis, or parasitic pneumonia.
Trichomonas (Trichomonas vaginalis). It infects the female urogenital tract. Symptoms differ between men and women. It is the causative agent of trichomoniasis, a sexually transmitted infection.
Trypanosomes (Trypanosoma brucei, Trypanosoma cruzi). The first type of parasite affects the central nervous system, blood and lymph. It is transmitted by the tsetse fly and causes the so-called sleeping sickness. The second parasite causes Chagas disease by affecting the blood, muscles, nerves, heart, esophagus, and intestines. Also transmitted by insect bites.
How to treat infections caused by protozoan parasites in humans?
The treatment plan for a protozoan parasite infection will depend on the specific diagnosis. Typically, your doctor will prescribe medications, for example, to treat trichomoniasis, giardiasis, or cryptosporidiosis. Usually, drugs are not prescribed for toxoplasmosis unless there are conditions for this in the form of pregnancy, some other illness, or a severe and prolonged infection.
The doctor may also recommend other treatments to help relieve symptoms. For example, many parasitic infections can cause diarrhea, which often leads to dehydration. Therefore, when treating an infection caused by protozoa parasites, it is usually recommended to drink plenty of fluids to replenish the loss in the body.
How can protozoan parasites be prevented?
There are several steps you can take to reduce your risk of contracting a parasitic infection:
- practice safe sex using a condom;
- wash your hands regularly, especially after handling raw food or faeces;
- Cook food to the recommended core temperature.
- drink clean water, including bottled water, when you travel;
- avoid swallowing water from lakes, streams or ponds;
- avoid cat litter and feces during pregnancy.
If you suspect you have a parasitic infection, make an appointment with your doctor. They can help diagnose the cause of your symptoms and recommend a treatment plan. The sooner you start treatment, the sooner you can help stop the spread of the infection to others.