Many protozoa live in the human body. Many of them are pathogenic. Our story is about ten of them, most of them. The critique is based on both historical and recent publications.
Larger. BalantidiumBalantidium coli
The largest protozoan is a human parasite and the only ciliate in this company. Its dimensions range from 30 to 150 microns in length and from 25 to 120 microns in width. In comparison: the length of plasmodium malaria at the largest stage is about 15 microns and several times shorter than the balantidium of intestinal cells, among which lives the infusoria. An elephant in a shop in China.
Distributedwhere there are pigs - its main carriers It usually lives in the submucosa of the colon, although in humans it also occurs in the pulmonary epithelium. It feeds on bacteriaB. coli, food particles, fragments of the host epithelium. In animals, the infection is asymptomatic. People can develop severe diarrhea with bloody, mucous discharge (balantidiasis), sometimes ulcers form on the walls of the colon. It is rare to die of balantidiasis, but it causes chronic fatigue
People are contaminated with dirty water or foods that contain cysts. The rate of infection in humans does not exceed 1%, while pigs can be infected worldwide.
Treatedwith antibiotics, no drug resistance reports for this ciliate have been reported yet.
Discoveredby Swedish scientist Malstem in 1857. Today, balantidiasis is associated with tropical and subtropical regions, poverty and poor hygiene.
The first. Oral amoebaEntamoeba gingivalis
The first parasitic amoeba found in humans. The description of amoebas was published in 1849 in the oldest scientific journal. Amoeba was found in dental plaque, hence the name from the Latin gums - gums.
Livesin the mouth of almost all people with toothache or sore throat, inhabits pockets and plaque. It feeds on epithelial cells, leukocytes, microbes and in the case of erythrocytes. It is rare in people with a healthy oral cavity.
This small protozoan, 10-35 μm in size, does not enter the environment and does not form cysts, it is transmitted to another host by kissing, through dirty dishes or contaminated food. E. gingivalis is considered a purely human parasite, but is sometimes found in captive cats, dogs, horses and monkeys.
In the early twentieth century,E. gingivaliswas described as the causative agent of periodontal disease, as it is always present in inflammatory dental cells. However, its pathogenicity has not been proven.
The drugsthat affect this amoeba are unknown.
The most common. Dysentery amoebaEntamoeba histolytica
This intestinal parasite with blood penetrates the tissues of the liver, lungs, kidneys, brain, heart, spleen, genitals. It eats what it takes: food particles, bacteria, red blood cells, leukocytes and epithelial cells.
Distributedeverywhere, especially in the tropics. Usually, people become infected by swallowing a bladder.
In temperate countries, the amoeba tends to remain in the intestinal tract and the infection is asymptomatic. In tropical and subtropical regions, the pathological process often begins:E. histolyticaattacks the walls. The reasons for the transition to the pathogenic form are still unclear, but several molecular mechanisms of what is happening have already been described. Thus, it is clear that amoebae secrete lysates, penetrate mucus and kill cells. Obviously, the amoeba can destroy the host cell in two ways: by causing apoptosis in it or simply by chewing pieces. The first method was considered the only one for a long time. Incidentally, the mechanism of cellular suicide at record speeds - in minutes - has not been determined. The second method was described quite recently, the authors called it roundness by the Greeks "three" - to gnaw. It is worth noting that the amoebae that bite the cells abandon their prey as soon as it dies. Others can phagocytose dead cells completely. It is assumed that the cells that bite and devour differ in the pattern of gene expression.
Now the ability of the amoeba to penetrate the bloodstream, liver and other organs is related to trogocytosis.
Remuneration is a deadly disease, with about 100, 000 people dying from E. histolytica infection each year. The amoeba of dysentery has a non-pathogenic twin,E. dispar, so microscopy is not enough to diagnose the disease.For treatmentmust be destroyed as mobileE. histolyticaand cysts.
E. histolytica was described and its pathogenic nature was determined in 1875 in a patient with diarrhea. The Latin name for amoeba was given in 1903 by the German zoologist Fritz Schaudin.Histolyticameans destructive tissues. In 1906, the scientist died of a lifelong intestinal abscess.
The most common. Enteric bulbsGiardia lamblia (G. intestinalis)
Giardia, the most common intestinal parasite, is ubiquitous. 3-7% of people in developed countries are infected and 20-30% in developing countries. That's about 300 million people.
The parasites livein the duodenum and bile ducts of the host, where they float, work with whips, and then attach to the epithelium with the help of a sticky disk located at the bottom of the cell. At 1 cm2the epithelium sticks to a million bulbs. They damage the villas, which impede the absorption of nutrients, causing inflammation of the mucous membranes and diarrhea. If the disease affects the bile ducts, it is accompanied by jaundice.
Giardiasis is a disease of dirty hands, water and food. The life cycle of the protozoan is simple: in the intestine there is an active form, and at the exit with feces there are stable cysts. To become infected, it is enough to swallow twelve cysts, which in the intestines will turn back into active form.The main secretof the ubiquitous presence of lamps in the variability of surface proteins. The human body fights the bulbs with antibodies and, in principle, is able to develop immunity. But people who live in the same area and drink the same water are infected again and again by the offspring of their own parasites. Why; Because during the transition from the active phase to the bladder and vice versa, the bulbs change the proteins in which antibodies are produced - specific variants of surface proteins. There are about 190 variants of these proteins in the genome, but only one is always present on the surface of a single parasite; the translation of the rest is interrupted by the RNA interference mechanism. And change happens about once every ten generations.
Treatedwith antiprotozoal agent with antibacterial action. The disease resolves in a week, but if the bile ducts become infected, relapses are possible for many years. Cysts are fought with iodine water.
DiscoveredGiardia lambliain 1859 by the Czech scientist Vilém Lambl. Since then, the simplest has changed several names and today has received in honor of the analyst and French parasitologist Alfred Giar, who did not describe the lamps.
And the first sketch of Giardia was made by Anthony van Leeuwenhoek, who found it in his own upholstered chair. It was 1681.
By the way, Giardia is also very evolutionarily ancient, it comes almost directly from the ancestor of all eukaryotes.
The most familiar. Trichomonas vaginalisTrichomonas vaginalis.
The simplest, which is sexually transmitted. It lives in the vagina, and in men - in the urethra, epididymis and prostate, it is transmitted sexually or through wet towels. Babies can be infected by passing through the birth canal. The T. vaginalis has 4 lashes on the front end and a relatively small corrugated membrane. if necessary, it releases pseudopods. The maximum size of Trichomonas is 32 by 12 microns.
Trichomonas is more commonthan the combination of chlamydial, gonorrhea and syphilis causative agents. It affects about 10% of women, and probably more, and 1% of men. The latter form is unreliable because it is more difficult to detect the parasite in men.
T. vaginalis feeds on microorganisms, including lactic acid bacteria of the vaginal microflora, which maintain an acidic environment, thus creating an optimal pH for itself above 4. 9.Trichomonas destroys mucous cells, causing inflammation. About 15% of infected women complain of symptoms.
Treatedwith antibacterial medicine. As a precautionary measure, regular absorption with diluted vinegar is recommended.
Describedin 1836 by the French bacteriologist Alfred Donne. The scientist did not realize that there was a pathogenic parasite in front of him, but determined the size, appearance and type of the simplest movement.
The most deadly. The causative agent of sleep sicknessTrypanosoma brucei
The causative agent of African sleep sickness is the deadly protozoan. An infected person dies without treatment. The trypanosome has an elongated whip length of 15-40 μm. There are two subspecies that can not be distinguished externally. Disease caused byT. brucei gambiense, lasts 2-4 years. T. brucei rhodesienseis a more contagious, transient pathogen from which they die after a few months or weeks.
Distributedin Africa, between the 15th parallel of the Southern and Northern Hemispheres, in the natural area of the vector - blood-sucking insects of the genusGlossina(tsetse fly). Of the 31 species of fly, 11 are dangerous to humans. Sleep sickness affects the population of 37 countries south of the Sahara at 9 million km2. Up to 20 thousand people get sick every year. There are now about 500, 000 patients, 60 million of whom are at risk.
From the fly intestineT. bruceienters the human bloodstream, from there it enters the cerebrospinal fluid and affects the nervous system. The disease begins with fever and inflammation of the lymph nodes, followed by lethargy, drowsiness, muscle paralysis, exhaustion and irreversible coma.
Mortality of the parasite is related to its ability to cross the blood-brain barrier. The molecular mechanisms are not fully understood, but it is known that when it enters the brain, the parasite secretes cysteine proteases and also uses some host proteins. In the central nervous system, on the other hand, the trypanosome is used by immune agents.
The first description of sleeping sickness in the upper reaches of Niger was made by the Arabic scholar Ibn Khaldun (1332-1406). In the early 19th century, Europeans already knew the initial sign of the disease - swelling of the lymph nodes in the back of the neck (a symptom of Winterbottom) and slave traders paid special attention to it.
T. brucei was discovered by the Scottish microbiologist David Bruce, after whom it was named, and in 1903 he first established the link between drill bits, tsetse fly and tsetse fly. .Treatmentdepends on the stage of the disease, drugs cause serious side effects. The parasite has high antigenic variability, so it is impossible to create a vaccine.
The most exaggerated. LeishmaniaLeishmania donovani
Leishmanias has earned the title of the most exaggerated parasite because they live and reproduce in macrophages - cells designed to destroy parasites.L. donovaniis the most dangerous of these. It causes visceral leishmaniasis, common dumdum or kala azar fever, from which almost all patients die without treatment. But survivors gain long-term immunity.
There are three subspecies of the parasite.L. donovani infantum(Mediterranean and Central Asia) mainly affects children, dogs are often its reservoir.L. donovani donovani(India and Bangladesh) is dangerous for adults and the elderly, has no natural reservoirs. The American L. donovani chagasi (Central and South America) can live in the blood of dogs.
L. donovani- whip longer than 6 microns. Humans become infected after being bitten by mosquitoes of the genusPhlebotomus, sometimes through the sexual contact of babies - who pass through the birth canal. Once in the bloodstream,
Symptoms of the disease- fever, enlarged liver and spleen, anemia and leukopenia, which contribute to secondary bacterial infection. Every year 500 thousand people get sick with visceral leishmaniasis and about 40 thousand die.
Treatmentheavy - intravenous administration of antimony preparations and blood transfusions.
The taxonomic relationshipL. donovaniwas defined in 1903 by renowned malaria researcher and Nobel laureate Ronald Ross. It owes its general name to William Leishman and the specific name to Charles Donovan, who in 1903 himself discovered independent protozoan cells in the spleen of patients who died from kala azar, one in London, the other in Madras.
The most difficult life cycle.Babesia spp.
Babies, in addition to multilevel asexual reproduction in mammalian erythrocytes and sex mites in the intestines of the genusIxodes, complicate their development by metabolic transmission. From the intestines of a female tick, protozoan sporozoites penetrate the ovaries and infect the embryos. When the mite larvae hatch, the mosaic passes into their salivary glands and, with the first bite, enters the blood of the vertebrates.
DistributedBabesia in America, Europe and Asia. Their natural reservoir is rodents, dogs and cattle. A person is infected with several types: B. microti, B. divergens, B. duncaniandB. venatorum.
Symptoms of Babesiosis resemble malaria - recurrent fever, hemolytic anemia, swollen spleen and liver. Most people recover spontaneously, for patients with weakened immune systems, babesiosis is fatal.Treatment methodsare still being developed, with antibiotics and, in severe cases, blood transfusions being prescribed.
Babesia is described by the Romanian microbiologist Victor Babes (1888), who discovered it in sick cows and sheep. Babesia has long been considered an animal pathogen until it was discovered in 1957 in a Yugoslav shepherd who died of an B. divergens infection.
The most important. The causative agent of toxoplasmosisToxoplasma gondii
T. gondiiis the most powerful parasite as it controls the behavior of vectors.
Distributedeverywhere, evenly distributed. In France, for example, 84% of the population is infected, in the United Kingdom - 22%.
Toxoplasma life cycle consists of two stages: sexual appearance occurs in the body of any warm-blooded, sexual reproduction is possible only in the epithelial cells of the cat's intestine. ToT. gondiicould complete development, the cat must eat an infected rodent. Increasing the chance of this happening,T. gondiiblocks the rodents' natural fear of smelling cat urine and makes it attractive by targeting a group of neurons in the amygdala. How he does it is unknown. One of the supposed mechanisms of action is a local immune response to infection. It changes cytokine levels, which in turn increase the levels of neuromodulators such as dopamine. Toxoplasma also affects human behavior, which manifests itself even at the population level. Thus, in countries with high levels of toxoplasmosis, neuroticism and a desire to avoid uncertainty, new situations are more common. It is possible that infection withT. gondiiwill lead to cultural changes.Infectionin humans is often asymptomatic, but with weakened immunity, it destroys cells in the liver, lungs, brain, retina, causing acute or chronic toxoplasmosis. The course of the infection depends on the infectious action of the strain, the state of the host's immune system and its age - older people are less susceptible toT. gondii.
Treatmentof toxoplasmosis with antiprotozoal drugs.
Describedin 1908 in desert rodents. This honor belongs to the staff of the Pasteur Institute in Tunisia Charles Nicolas and Luis Manso.
Most pathogens. Malaria PlasmodiumPlasmodium spp.
Plasmodium malaria is the most pathogenic parasite in humans. The number of malaria patients can reach 300-500 million and the death rate during epidemics - 2 million. The disease still requires three times as many lives as armed conflict.Five types of Plasmodium cause malaria in humans:Plasmodium vivax, P. falciparum, P. malariae, P. ovaleandP. knowlesi, which also affects macaques.
Distributedin the area of vectors - mosquitoesAnopheles, which need a temperature of 16-34 ° C and relative humidity above 60%.
A comparison of the genome of the most infectious plasmodium,P. falciparum, with the plasmodium gorilla suggests that humans were infected by its ancestor from these monkeys. The emergence of this form of Plasmodium is related to the emergence of agriculture in Africa, which has led to an increase in population density and the development of irrigation systems.
Sexual reproduction of plasmodia occurs in the intestines of mosquitoes and in the human body is an intracellular parasite that lives and reproduces in hepatocytes and erythrocytes until the cells burst. 1 ml of patient blood contains 1 - 50 thousand parasites.The disease manifests itself as inflammation, recurrent fever and anemia, in case of pregnancy it is dangerous for the mother and the fetus. Erythrocytes infected withP. falciparumclog capillaries and in severe cases ischemia of internal organs and tissues develops.
Treatmentrequires a combination of many drugs and depends on the specific pathogen. Plasmodium becomes drug resistant.