Rickettsia is what? What diseases cause rickettsia?

In 1906, H. Ricketts began research spotted fever. In 1909, microorganisms in the form of rods with very small sizes were found in the studied blood preparations. Similar organisms were discovered this year by another researcher, S. Nicole, only when studying typhoid fever. And since Ricketts died in 1910 just because of typhoid fever, having told before about it about his discovery, the genus of the causative agents of this disease was named in his honor - Rickettsia, as a recognition of the scientist's merit before science.

What is Rickettsia?

Rickettsia are small gram-negative organisms with the properties of both viruses and bacteria. From the first, they took the possibility of reproduction only inside the eukaryotic cells, but at the same time, like bacteria, they need oxygen, have a cell wall and are sensitive to a certain group of antibiotics. These microorganisms are prokaryotes, they lack a formed nucleus, and there are no mitochondria.

Description and morphology

Usually all representatives of this genus with small sizes - up to 1 micron. Most often have a rod-shaped shape, but at certain stages it can be filiform and bacillary. And all the changes occur inside the host cells.

Rickettsia are immobile microorganisms, they do not have flagella, and under adverse conditions form small forms that protect them. Often, such forms can be in the body for up to 10 years, remaining and, under favorable conditions, again activated.

Rickettsia, chlamydia, mycoplasmas parasitize in a human cell, causing disease, but, after getting into the environment, they immediately die. Their habitat is a living cell with active metabolism. And if the mucous membrane of the mouth, pharynx and genitourinary system prefer mycoplasmas, rickettsia live in the epithelial cells and endothelium of the intestinal vessels of their main hosts - insects, and in humans all organs and tissues are affected. Chlamydia also prefer to settle in the organs of vision, affect the genitals and lungs.

Propagation, like viruses, rickettsia inside the host cell, only by dividing the maternal cell in half (which is characteristic of bacteria). In this case, cells infected with a parasite quickly die.

The life cycle of these microorganisms is very simple. This is either the vegetative stage - the cell is actively divided, or the stage of rest.

On the European continent, infections caused by rickettsia are relatively rare. But on the Asian continent, in Australia and in Tasmania, these infections are widespread.

Classification

As of May 2015, 26 species were included in this genus. At the same time, several species that were treated here earlier were excluded and transferred. It should be said that the classification of rickettsia, generally accepted by the world's luminaries, has not been fully developed.

The study of these microorganisms is very dangerous, since almost all representatives of this genus cause diseases, including fatalities. Thus, a lot of cases of infection of researchers involved in the study of these microbes.

Rickettsiosis

In humans, rickettsia is caused by febrile illness. And the common name of all these diseases is rickettsiosis. As a rule, their passage is very acute and is accompanied by various types of rashes on the skin, thrombovasculitis or vasculitis.

So what diseases cause rickettsia? To date, there are the following:

1. Epidemic typhus, the second name - typhoid fever.
2. Brill-Zinsers disease, or parodic typhus (rickettsia typhus, after a person has been ill for the first time, take a small form, in years and even decades, a relapse of the disease is possible, which received the given name). Most often observed in the elderly.
3. Endemic rash or rat typhus.
4. Brazilian typhus.
5. North Asian and Australian tick-borne rickettsiosis.
6. Spotted fever of the Rocky Mountains.
7. Vesicle rickettsiosis.
8. The Israeli fever (also called the Marseille fever and Mediterranean spotted fever).
9. Mouse typhus (the second name is flea, since fleas are a reservoir for transfer).
10. Quintan.
11. Tsutsugamushi, or Japanese fever (the main carriers of infection are rodents and reddish mites).
12. Malayan Scraping Typhoid.
13. Sumatran tick-borne typhus.
14. TIBOLA, or tick-borne lymphadenopathy - is a disease that was discovered only recently, as well as the following.
15. DEBONEL, or necrotic, scapalymphadenopathy (caused by the same species of rickettsia.) Diseases differ only in symptoms.

In addition, it is known:

• Ku fever;
• Trench fever;
• Rasquetsiosis (also called vesicle rickettsiosis);
• Queensland typhus:
• Astrakhan rickettsial fever.

This list is an incomplete list of diseases that people can get.

Ways of infection

Outside the cells of rickettsia - this is very unstable to the adversities of the outside world and rapidly dying from the influence of various factors, microorganisms. That's why they need special carriers. For this role blood sucking insects, such as fleas, lice and ticks, are great.

Since lice and fleas are found everywhere, the diseases that they carry are epidemic, while mites have their own specific area and the diseases caused by them are endemic.

Through a sting of an insect, a rickettsia enters the human body. Pathogens from the mucous membrane of the gastrointestinal tract, lice or mites pass into the blood, and the result is a fever and a serious illness. And for the arthropods themselves, rickettsia is rarely dangerous. There are cases of transmission of parasitic microbes by insects from generation to generation through eggs. Here arthropods are used simply as a reservoir for storage of microorganisms. And the infection of an insect can occur through the blood of a sick person during a bite.

If the ticker is a vector of the rickettsia, the pathogen can be obtained through a bite if the microorganism is in the salivary glands, or through rubbing into the skin when the insect is simply crushed.

There is a special subspecies, more resistant to environmental conditions, called Coxiella. They provoke these rickettsia diseases both through insect bites and airborne droplets and cause most often one of three types of Ku fever.

And Japanese fever is not transmitted directly from the patient to a healthy person. Required availability of an intermediary. And most often in his role is a rat or mouse. Their bite can be very dangerous.

Symptoms of diseases

Diseases caused by rickettsia, can manifest themselves in different ways, but the general symptoms can still be identified. They are as follows:

• Headache and muscle pain of incomprehensible origin;
• fever;
• Different types of rashes, and at the place of the insect bite a small scab is formed, which eventually blackens, when pressed on it, its stiffness is felt;
• Inflammation of the lymph nodes and their increase in size;
• dry cough.

Severe rickettsiosis usually always takes place with fever and delirium, the patient's breathing is difficult and difficult. Diagnosis of pathology is often a great difficulty. The diagnosis can be made thanks to a biopsy of the skin from the bite site. On its surface during infection, a papule is always formed, which then turns black.

The fever begins about the fourth day after infection, but its appearance may be postponed for a longer period. The patient develops a state of apathy. Lymph nodes (first those that are next to the bite, then the rest) are inflamed and increase in size.

A week after the first signs of the disease, typical signs of rickettsiosis begin to appear - severe heat and dry cough that develops into bronchitis or pneumonia, there is photophobia, conjunctivitis. Perhaps because of the heat develop delusional state, as well as partial or complete loss of hearing. On the skin there is a small-scaby rash, especially on the limbs, but sometimes on the body.

If you do not start treatment, then the febrile state will persist for two weeks. The possibility of a lethal outcome is up to 40% of all cases of infection. And the risk of death depends on the age, type of disease and immune capabilities of the human body.

Microbiological diagnostics

Early diagnosis makes it possible to speed up the treatment process. A quick diagnosis of rickettsia is a biopsy of the scab. But it can only be confirmed with antibodies secreted from mice after the inoculation of the blood of a sick person.

Another way of diagnosing is with the serological method. But the results should be interpreted with great care, because often occurs between strains of different types of bacteria, cross-activity.

One of the most common tests for revealing rickettsia is the Muser-Neil test. In this case, the venous blood of the patient is introduced into the abdomen of the guinea pig at an early febrile stage. If the disease is confirmed, the animals have symptoms of fever, necrosis of tissues, and in males the swine is swollen with a scrotum. Most often, if the diagnosis is confirmed, the animal dies.

Immunity with rickettsiosis

Even with such small dimensions, this genus of microorganisms possesses certain antigens (AH), most often lipopolysaccharide nature. The same AH is found in the rickettsia of the Proteus bacterium, which is located far enough in the systematic table from the Rickettsia genus. Therefore, if a person has suffered one of the diseases caused by any species of this genus, other pathogens of the same genus, bearing the same antigen, are no longer frightening. After all, the human body develops cross immunity.

Treatment

Depending on the illness, the methods of treatment are selected. And only a qualified infectiologist can make the right diagnosis and prescribe a treatment. For various rickettsial fevers, administration of antipyretic agents is prescribed, for example, "Aspirin", "Prednisolone" or another glucocorticosteroid, an antibiotic ("Rifampicin" or "Levomethicin").

At the same time, it is necessary to detoxify the body by infusion, during 3 days of haemodesis, intravenously for 3 days, glucose solution and drink abundantly up to 2.5 liters per day of Oralite solution for five days.

With this scheme of taking medicines, the temperature returns to normal on the 9-11th day. After about two weeks, the body aches and pains in the muscles were removed, and after three weeks the rash on the body disappeared, which meant almost complete recovery.

For the treatment of tick-borne typhus, another treatment scheme is proposed:

• Reception of antibiotics tetracycline and (or) levomitsetinovoy group, for maintenance - cardiovascular agents in moderate dosage.
• If the disease begins to be aggravated by a delusional condition, or other severe symptoms are noted, an additional 5-percent glucose solution is injected intravenously to reduce the body's toxicity.
• In rare cases, hormones and cardiac glycosides are additionally administered.

With this treatment, a full recovery occurs approximately in a month.

Ku fever is treated with ingestion of antibiotics, "Levomycetin" and the drug tetracycline group simultaneously. If no improvement is observed within three to four days, glucocorticoid preparations are additionally administered. With the appearance of such a side effect as the myocardium, cardiac and vasopressor preparations are additionally introduced. Means of detoxification are administered intravenously (glucose and saline). The treatment lasts about half a month.

Treatment of rickettsiosis must necessarily take place in a hospital, under the supervision of infectious diseases. It is much more difficult to treat the diseases that caused rickettsia, chlamydia in pregnant and lactating women, since this group of patients is contraindicated in taking the tetracycline group of drugs. In this case, a more sparing, but less effective, "Chloramphenicol" is used (breast-feeding for the duration of treatment should be discontinued).

Children under eight with rickettsiosis are treated with "Chloramphenicol" for ten days, and older adults, as well as adults, doxycycline group, only take a smaller dose.

Prevention

To date, the vaccine has been developed and used in medicine atenuated from epidemic typhus and against Ku-fever.

But not everyone has the opportunity to vaccinate, going on vacation to countries where there are foci of infection with rickettsiosis. Therefore, by following a few simple rules, you will be able to protect yourself and your family from them.

1. If you go to a park, square, forest, zoo or any other place where contact with mites, fleas or other vectors is possible, wear long sleeves and a broad-brimmed hat on your head.
2. Be sure to use the means that drive away insects.
3. Be sure to examine yourself and your children for insect bites. Pay special attention to the nape, inguinal area, armpits and places under the knees - the favorite place of tick bites.
4. When visiting places that are infected with any rickettsiosis, be sure to wear clothing impregnated with dimethyl phthalate.
5. Do you like to spend the night in the countryside in tents? Then sleep on the cot, not on the ground.
6. Have suspicions of a disease of someone close to rickettsiosis? Immediately, without hesitation, contact the infectious disease specialist.
7. Compliance with the rules of personal hygiene has not been canceled.