The simplest human parasites: table

Human parasites are represented by different groups, one of which is protozoa. They are capable of causing diseases of varying severity, and these microorganisms are not as easy to diagnose as groups with a more complex organization. For convenience, in the article they are presented in a table with the main characteristics.


The simplest include organisms with a primitive organization, which are combined into the Protozoa phylum. It has more than 15 thousand species, and some of them lead a parasitic lifestyle in the human body. All of them are characterized by small sizes, they can be seen only with a microscope, and it is impossible to notice them with the naked eye.

Many of the simplest parasites have an extremely primitive structure. Once in the host's body, they begin to multiply. Sometimes this happens by dividing into two halves, and sometimes by multiple division. In the latter case, the disease develops rapidly, symptoms quickly appear, sometimes capable of eventually even causing the death of a person.

Features of biology

The organism of protozoan human parasites consists of two main parts: the nucleus and the cytoplasm, in which all other organelles are located. The core can be one or more.

Protozoa have the ability to form a cyst if environmental conditions become unfavorable. Because of this, they are able to remain viable for a long time, remaining motionless and doing without nutrients. As soon as conditions return to normal, the cyst shell is destroyed, and the microorganism continues its normal functioning. Encystation also allows parasites to successfully spread from organism to organism.

All protozoa are divided into several categories depending on the anatomy, mode of movement and other characteristics:

  • flagella;
  • sarcode
  • sporozoans
  • ciliates.

Within each group, there are species for which humans are the intermediate or definitive host.

Main types

Parasites of the type Protozoa cause many diseases and parasitize in different organs. For convenience, they are presented in the table.

Name Infected body parts Method of infection Symptoms
Balantidia lower intestines Eating uncooked pork meat or water with cysts Balantidiasis is often accompanied by diarrhea. White mucus and bloody discharge appear in the feces. The colonic mucosa ulcerates, and in such cases, bleeding may increase. With the progress of the disease, exhaustion of a person occurs, in rare cases it can lead to death.
mouth amoeba Oral cavity, gum pockets, dental plaque A person becomes infected by kissing a carrier, using dirty dishes and eating contaminated food. It rarely affects people who do not have pathological lesions in the oral cavity. In inflammation, the oral amoeba feeds on epithelium, microbes, leukocytes and erythrocyte cells. May cause periodontal disease.
dysenteric amoeba Through the bloodstream it penetrates into the lungs, liver, heart, genitals, kidneys. Settles in the intestinal lumen Ingestion with food or water In some cases, the disease is asymptomatic. If the dysenteric amoeba attacks the intestinal walls, then the pathogenic stage begins. It is characterized by colitis, tissue necrosis, liver damage, abscesses may appear. Very severe consequences cause metastases to the brain and other organs. Possible fatal outcome. Sometimes the disease takes a relapsing course. Rarely self-healing occurs
Intestinal Giardia Duodenum and bile ducts. oral route Giardia stick to the mucous epithelium and damage the absorption of nutrients. Inflammation of the mucosa and constant diarrhea develop. If the infection covers the bile ducts, yellowness of the skin appears. Some people develop immunity to intestinal Giardia, especially in countries with a tropical climate.
Trichomonas vaginalis In women - on the vaginal mucosa, in men - in the epidermis of the prostate and in the urethra During sexual intercourse, as well as during childbirth from mother to child Trichomoniasis is manifested by foamy discharge, itching and burning on the mucous membrane of the genital organs, pain during sex, the appearance of bloody discharge from the urethra, etc. A complication of trichomoniasis is inflammation of the vulva due to the activity of protozoa, cystitis, prostatitis and infertility
Trypanosoma brussei Cerebrospinal fluid and the brain After being bitten by a tsetse fly, which is an intermediate host Begins with fever and swelling of the lymph nodes, continues with apathy, an overwhelming desire to sleep, muscle paralysis and exhaustion. If left untreated, coma and death occur.
Cutaneous leishmania Contact with a sick person or animal On the skin, most often on the face or hands The incubation period lasts from 2 months to 5 years, after which a brownish dense nodule appears at the site of the insect bite. It increases, and then a purulent ulcer opens in its place. The disease lasts up to several years, and then the final scarring of the wounds occurs. Complications can be disorders of the heart, kidneys and adrenal glands.
Toxoplasma Infected domestic animals, mainly cats, sometimes infection occurs when eating food with protozoa Liver, heart, eyes, brain In the congenital form - multiple pathologies of fetal development, death in infancy, mental retardation, multiple infections. Acquired toxoplasmosis provokes high fever, enlarged liver, headaches, vomiting, convulsions. Often takes a chronic course with increased fatigue and eye damage. Rarely occurs in a latent form
Isospora From an infected person with fecal-oral transmission epithelium of the small intestine The incubation period lasts about 10 days. Then the body temperature rises, vomiting and diarrhea appear. The disease is acute for a week or two, then recovery occurs
Crypto sporidia oral route Epithelial tissues of the intestine Incubation lasts about a week, then diarrhea begins, possibly with inclusions of spotting. The stomach may hurt, fever appears, signs of dehydration are possible. With insufficient immune status of the patient, infection can affect other organs: lungs, pancreas, stomach, etc.

Are worms the simplest

Sometimes you can hear the phrase that the patient is infected with the simplest worms. It must be understood that protozoa are exclusively unicellular microorganisms, in extreme cases, organizing colonies. But they are never multicellular like worms and helminths.

In protozoa, all processes occur within the cellular cytoplasm and cell nuclei, while in worms, the anatomical organization is much more complicated: they have differentiated organs that perform special physiological functions. Therefore, it is fundamentally wrong to classify worms as protozoa.

protozoan human parasite

Sometimes helminths are called the simplest parasites in comparison with insects: bedbugs, lice, etc. , since the latter are much higher up the evolutionary ladder. In this interpretation, the name of worms is allowed as protozoa.