Poliomyelitis: symptoms, consequences, prevention of poliomyelitis
- Causes of poliomyelitis
- How is poliomyelitis transmitted?
- Mechanism of disease development
- Symptoms of poliomyelitis
- Treatment of poliomyelitis
Poliomyelitis (children's paralysis) is a viral infectious disease with an alimentary transmission, which leads to the development of damage to the nervous system and paralysis of various muscle groups. Infection with viruses occurs mainly in childhood. To date, thanks to vaccination, the incidence of polio has been reduced to a minimum.
Causes of poliomyelitis
The causative agent of poliomyelitis is an enterovirus that belongs to the Picornaviridae family. The virus size is about 8-12 nanometers, it consists of one strand of RNA (genetic material) and a protein capsule. In the external environment, the virus is sufficiently stable, withstands freezing, in water it can maintain its viability up to 3 months, in faeces up to six months. Destructive to the virus is ultraviolet radiation (sunlight) and solutions of antiseptics (furacilin, chlorhexedin, bleach, hydrogen peroxide). There are three serological types of poliomyelitis causative agent - I (leading to outbreaks of the epidemic with the development of paralysis), II (leads to infrequent sporadic cases of the disease) and III (high genetic variability, which can lead to the disease even after vaccination). All types of the poliomyelitis virus are tropic to the nervous tissue, they parasitize the motor neurons of the gray matter of the spinal cord and brain.
How is poliomyelitis transmitted?
The source of the infection of poliomyelitis is only a person (anthroponous infection) - a patient (including asymptomatic forms) and a virus carrier. In the external environment, the virus is excreted with human feces or saliva at the initial stages of the development of the disease. It can persist for a long time in soil and water. Infection occurs in several ways:
- Air-droplet path - is realized by inhalation of air with viruses weighed in it.
- Alimentary route of transmission - infection occurs when eating contaminated food.
- Contact-household way - is possible when using one dish for food intake by different people.
- Waterway - the virus enters the body with water.
To the disease with poliomyelitis children in the age of 3 months to 2 years are most susceptible, in whom immunity is still insufficiently formed. The highest incidence of poliomyelitis persists in countries with a hot humid climate (Southeast Asian countries, Asia, India, Armenia, Azerbaijan, Bulgaria, Turkey). Poliomyelitis is characterized by seasonality with an increase in the incidence rate in the spring-summer period. After the infection, a stable type-specific immunity remains.
Mechanism of disease development
The entrance gates of infection are the mucous membranes of the pharynx and the intestine. After the penetration of the poliomyelitis virus into the body, its development begins, in which 4 phases are distinguished:
- Enteral phase - primary reproduction (replication) of virus particles occurs in the cells of the intestinal mucosa (enterocytes).
- Lymphogenous phase - the virus from the cells of the intestine and pharyngeal penetrates into the mesenteric lymph nodes or lymphoid tissue, where its replication continues.
- Viralemia - characterized by the release of viral particles from the lymphoid tissue into the blood and its spread throughout the body. From the blood, viral particles penetrate into the cells of the liver, spleen, lungs, heart, bone marrow. In the cells of these organs there is a further replication and repeated release of virus particles into the blood (secondary viremia).
- The neural phase is the transfer of viruses from the blood into the motor neurocytes (cells of the nervous system) of the anterior horns of the spinal cord and motor nuclei of the brain. Parasitizing in neurocytes, viruses cause their damage and death with the development of the inflammatory process. Later, the area of dead nerve cells is replaced by a connective tissue.
Expression and localization of paralysis (absence of movements in skeletal muscles due to damage to motor neurocytes) depend on the number of viral particles and their preferential location in the organs of the central nervous system.
Symptoms of poliomyelitis
The incubation period of poliomyelitis lasts 7-12 days (cases of a longer incubation period up to 35 days are known). Depending on which groups of symptoms prevail in the clinical course of poliomyelitis, several of its main forms are distinguished:
- A typical form with lesions of the central nervous system (non-paralytic and paralytic).
- Atypical form (erased or asymptomatic).
Also, the clinical picture of poliomyelitis is characterized by severity, a light, moderate and severe course.
Symptoms of a typical paralytic form
For the clinical symptomatology of this form of poliomyelitis is characterized by the presence of several periods, which follow one after another:
- The pre-paralytic period lasts from the onset of the manifestations of the first clinical symptoms after the incubation period to the development of paralysis, on average it takes a period of 1 to 6 days. During this period, symptoms of general intoxication develop (associated with the release of viral particles into the blood) - increase in body temperature to 38º C and above, headache and aching muscles and joints. Also, abdominal pain, vomiting and diarrhea are added. There is and is growing pain in the striated muscles.
- The paralytic period is characterized by rapid, within 24-36 hours, development of paralysis (paresis) of individual groups of skeletal muscles, with their weakness and atrophy (decrease in muscle mass). If the neurocytes of the anterior horns of the spinal cord are affected, paralysis of the legs or hands on one side (spinal form) develops. When the viral infection of the motor neurons of the cranial nerves is localized, the paresis of the muscles of the face and soft palate develops with the appearance of a nasal voice and the inability to swallow food normally. There are cases of isolated damage to the motor cells of the motor nucleus of the facial nerve, in which paralysis of mimic muscles with asymmetry of the face, incomplete closure of the mouth and eyes develops.
- The recovery period (reconvalescence) - as the body is freed from the virus and the motor function of the neurocytosis is restored, the muscles, movements in them and volume are gradually restored.
- Residual period (the period of residual phenomena) - this period is the longest, characterized by residual phenomena in the form of muscle contracture, deformation of the spine, muscle atrophy, flaccid paralysis. Such phenomena can remain with a sick person throughout life.
Symptoms of a typical non-paralytic form
This clinical form is characterized by a sharp onset of the disease with an increase in body temperature and the phenomena of general intoxication. Then, for several days, symptoms of irritation of the brain envelopes are added-a severe headache, increased sensitivity to auditory (hyperacus) and visual (photophobia) stimuli, stiff neck (their resistance when trying to tilt the head forward). This clinical form is favorable in connection with the absence of paralysis of skeletal muscles. Within 2 weeks all the symptoms gradually disappear.
Symptoms of atypical form
The course of the atypical form of poliomyelitis can be erased and asymptomatic. The aborted course is characterized by the appearance of several symptoms at the end of the incubation period:
- An acute onset with manifestations of general intoxication and an increase in body temperature.
- Dyspeptic syndrome - bloating, diarrhea, abdominal pain, decreased appetite.
- The syndrome of vegetative dysfunction is a decrease in the motor activity of a person (adynamia), general weakness, sweating, pallor of the skin.
- Catarrhal phenomena in the form of a small cough, sore throat, runny nose with a small amount of clear mucus.
The duration of this form is 3-5 days, which in the pathogenesis of infection corresponds to the period of the release of the virus into the blood. In the future there is a reverse development of symptoms without the formation of paralysis. For asymptomatic flow, there is a complete absence of any symptoms of poliomyelitis in the presence of a virus in the body, which can be confirmed only by laboratory methods of investigation.
To suspect the development of poliomyelitis allow epidemiological data and characteristic clinical symptoms. The final diagnosis is made based on the isolation of the virus or antibodies to it using laboratory diagnostics, which includes:
- Determination of the presence of the poliomyelitis virus in stool or cerebrospinal fluid by polymerase chain reaction (PCR).
- Immunoenzyme analysis (ELISA) for rapid diagnosis and detection of viral RNA.
- A serological study of blood plasma, which allows you to identify antibodies to the poliovirus in it.
Additionally, to assess structural changes in the motor centers of the brain and spinal cord, a clinical analysis of cerebrospinal fluid and computer or magnetic resonance imaging are performed.
Treatment of poliomyelitis
Regardless of the severity of the course and the severity of clinical symptoms, if there is a suspicion of the presence of poliomyelitis, hospitalization in a medical hospital is mandatory. The regime during the therapeutic events only bed, the diet includes vitamins, proteins and carbohydrates, with sufficient caloric content of food, it must be easily digestible. Therapeutic measures include drug etiotropic and pathogenetic treatment.
To date, there are no effective drugs and drugs that destroy the virus. In the early stages of the disease, at the time of active replication of the virus, drugs are used based on recombinant interferons (reaferon, viferon), which suppress the assembly of virus particles inside the cell.
Treatment is aimed at reducing the inflammation in the central nervous system (non-steroidal anti-inflammatory drugs), reducing the swelling of the brain and spinal cord (diuretics), restoring the neurocytes (neuroprotectors) and the use of vitamins. Also, to improve the motor function of paralyzed muscles, physiotherapy is used, including mud baths, paraffin applications, and magnetotherapy.
To prevent the development of poliomyelitis vaccination is used, which is carried out with the help of live attenuated viruses - they can not cause the development of the disease, but cause a specific immune response of the body with the formation of long-term stable immunity. To this end, in most countries of the world, poliomyelitis vaccination is included in the mandatory vaccination calendar. Modern vaccines are polyvalent - contain all 3 serological groups of the poliovirus.
The outcome of the disease with polio depends on its form and the severity of the course. After the transferred paralytic form, residual effects in the form of flaccid paralysis and muscle atrophy can remain. The urgency of this infection remains high today. In countries with warm and humid climates, outbreaks of poliomyelitis among children are periodically recorded.
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