Toxoplasma is a genus of parasitic eukaryotes, which includes only one reliably studied species - Toxoplasma gondii. This microorganism is able to invade any animal or human cells, including nervous, epithelial, brain and cardiac tissue. He does not need oxygen for life, because he is anaerobic. The main host of toxoplasma are representatives of the cat family, in the body of which it goes through several stages of development, turning into an adult cyst. Cats are a kind of incubator, secreting eukaryotic eggs along with feces. And as an intermediate host, a variety of warm-blooded animals, including humans, can be selected.
Pathogen disease
Toxoplasma, the life cycle of which goes through several stages, causes a disease called toxoplasmosis. In humans, this disease usually proceeds surprisingly easily and without severe symptoms. But if you become infected during pregnancy or at a time when immunity is lowered (for example, if you have HIV), it can cause serious consequences and even lead to death.
Microorganism structure
The shape of an adult is similar to a crescent. Special processes are located on the front, with the help of which the toxoplasma is attached to the internal organs of the host. It does not have organelles, but even without them it can perfectly move by sliding, and also penetrate into tissue cells in a corkscrew fashion.
Microorganism life cycle diagram
The toxoplasma life cycle can be briefly described in two different conditions:
- its presence in the intestines of a cat;
- release of eggs into the environment.
It is possible that the entire development of the microbe can take place only in the body of the same cat. In an adult, the parasite forms gradually, moving from one phase of development to another. The life cycle of the toxoplasma, the scheme of which is shown in the picture, consists of sequential forms acquired by the pathogen. As he grows up, which lasts several years, he goes through four of them: trophozoite - pseudocyst - tissue cyst - oocyst (fertilized egg). The formation of a mature individual also takes place in several stages:
- schizogony - division of the cell nucleus and the formation of many daughter merozoites;
- budding - the formation of two new microorganisms in the membrane of one mother cell;
- gametogony - sexual reproduction by fusion;
- sporogonia - separation of the zygote formed after sexual reproduction .
Life Cycle Phases: Asexual
The asexual part of life takes place in the intermediate host. This may be, again, a cat or any other warm-blooded animal, bird or reptile. Once in the body, trophozoites are introduced into muscle and brain cells, where they form cellular vacuoles with firewalls, which, in turn, turn into pseudocysts. Gondia toxoplasma cannot be detected by the human or animal immune system, since cysts are hidden inside the body’s native cells. And its resistance to antibacterial drugs is so different that sometimes it is impossible to destroy all cysts in the tissues. Propagating inside vacuoles, it by division produces rapidly multiplying tachyzoites. The host’s native cell bursts, and motile parasites come out, affecting an increasing number of healthy cells. Tachyzoites can be identified by the immune system and destroyed, but this is not enough to stop their spread.
Toxoplasma: life cycle. Sexual phase
The sexual and final phase of the life cycle of the microbe takes place in the body of cats - both domestic and wild. Tissue cysts can be swallowed by a cat with an infected bird or mouse. They, passing the stomach, affect the epithelial cells of the small intestine. There they reproduce already sexually, as a result of which oocysts with two spores and four unicellular embryos of the parasite, called sporozoites, appear.
Together with feces, the finished eggs are released into the environment. They retain the ability to live in the land, sand up to 2 years, if external factors do not favor their further development. Animals or people can easily swallow an oocyst by swallowing unwashed fruits or vegetables, uncooked or raw meat. It is they who become sources of infection of other hosts, including humans. Gondia toxoplasma is introduced into the intestinal cells and, together with the bloodstream, spreads throughout the body. In the internal organs, most often in the brain, cysts are formed, each of which contains hundreds of cystozoites - mononuclear microbes.
Infection pathways
Unlike cats, a sick person does not secrete pathogen cysts into the outside world, like other representatives of the fauna. Toxoplasma is a microorganism whose eggs can be found almost everywhere: on lawns, in fields, in the ground, grass, sand. In any places where cats used to defecate.
The pathogen can be picked up:
- From a sick cat, if its saliva, urine or feces are on the integument, the integrity of which is impaired. Therefore, be sure to wash your hands with soap before eating and after cleaning the cat tray.
- When eating half-baked meat of poultry or cattle (lamb, pork), insufficiently washed vegetables, berries, herbs and fruits.
- Flies and cockroaches in contact with feces of cats also act as carriers. After they come into contact with food, a person can become infected by eating spoiled food.
But catching toxoplasmosis from an ordinary domestic cat is not as easy as you might imagine.
First, the cat needs to be a carrier of toxoplasma.
Secondly, cysts are excreted in a certain period of time. Usually for several weeks along with feces of a cat, but only once in the entire life of the animal.
Symptoms of infection
Basically, a person does not feel any symptoms, but sometimes his health condition is violated, as with the flu. After a few days or months, the acute stage of the disease smoothly becomes chronic. In patients with immunodeficiency, infection can cause toxoplasmic encephalitis, pneumonia, or other inflammatory processes that cause the person to die. During pregnancy, toxoplasma, the life cycle of which goes through several stages and is not disturbed during the migration of the pathogen from the intermediate host to the main one, penetrates the placenta and affects the fetus. Often this leads to fetal death of the baby or to a miscarriage. It has been observed that infection contributes to a change in host behavior. The microorganism "makes" rats or mice less afraid of cats and even look for their place of residence.
The parasite does this in order to move to the next phase of the life cycle if the cat eats light prey. The relationship between schizophrenia and the presence of toxoplasma in the body was studied. Studies have shown that the presence of infection can affect the development of paranoia or other psychological changes.
Analyzes
After the initial infection, a person forms a stable and lifelong immunity to the microorganism. Immunoglobulins come to the person in the fight against infection. Antibodies are capable of:
- neutralize the toxins that the parasite produces;
- contact the cells of the pathogen;
- penetrate the placenta, partially forming a passive defense in the fetus.
IgG toxoplasma is detected in blood serum, cerebrospinal fluid, pulmonary sputum and other biological secrets. If these antibodies are found in the amount of 7/16 hl, then an additional study is carried out by a polymer chain reaction to detect the activity of infection. The presence of an acute period of the disease - primary infection - is indicated by the presence of the pathogen DNA in biological media. It is worth noting that in plasma, toxoplasma can not be detected in all cases, even with increased invasion.
Interpretation of Results
Toxoplasma IgG with the “+” sign and IgM c “-” indicates the development of stable immunity for life. Both indicators with a “+” sign indicate the presence of primary infection. And if IgM is positive, but IgG is negative, during pregnancy this may mean intrauterine infection of the fetus. The absence of lgm antibodies in the blood always indicates a negative result. Even if infection did occur, it happened a long time ago. Therefore, at the moment, it does not pose any danger to humans.
Toxoplasma, whose life cycle is so complex, is the causative agent of a serious illness. But in fact, almost any person in the world who lives side by side with a cat manages to "meet" her in childhood. The asymptomatic acute period of the disease does not attract attention, and the chronic form or carriage does not harm the person and other people around him. Toxoplasma is dangerous only when the pregnant woman was not infected earlier, but caught the infection while carrying the baby. Therefore, in childhood or at the stage of family planning, you should not limit yourself in communicating with cats - it is better to have a pet so that the body develops a lifelong protection against infection. This will help preserve the health of the future fetus and protect it from deadly pathology.