Poliomyelitis: symptoms, consequences, prevention of poliomyelitis
- Causes of Polio
- How is polio spread?
- Mechanism of development of the disease
- Polio symptoms
- Poliomyelitis treatment
Poliomyelitis (infantile paralysis) is a viral infectious disease with alimentary transmission that leads to the development of damage to the nervous system and the paralysis of various muscle groups. Infection with viruses occurs predominantly in childhood. Today, thanks to vaccination, the incidence of polio has been reduced to a minimum.
Causes of Polio
The causative agent of polio is enterovirus, which belongs to the family Picornavirus (Picornaviridae). The size of the virus is about 8-12 nanometers, it consists of a single strand of RNA (genetic material) and a protein capsule. In the external environment, the virus is fairly stable, can withstand freezing, it can maintain its viability in water for up to 3 months, in feces up to six months. Ultraviolet radiation (sunlight) and antiseptic solutions (furatsilin, chlorhexedine, bleach, hydrogen peroxide) are detrimental to the virus. There are three serological types of the causative agent of poliomyelitis - І (leads to epidemic outbreaks with the development of paralysis), ІІ (leads to infrequent sporadic cases of the disease) and ІІІ (it has a high genetic variability, due to which it can lead to a disease even after vaccination). All types of poliovirus have tropism for nervous tissue, they parasitize the motor neurons of the gray matter of the spinal cord and brain.
How is polio spread?
The source of poliomyelitis infection is only human (anthroponotic infection) - the patient (including asymptomatic forms) and the virus carrier. In the external environment, the virus is excreted with human feces or saliva in the initial stages of the disease. It can persist in soil and water for a long time. Infection occurs in several ways:
- The airborne path is realized by inhalation of air with viruses suspended in it.
- Alimentary transmission - contamination occurs when eating contaminated food.
- Contact-household way - possible when using the same dishes for eating by different people.
- Waterway - the virus enters the body with water.
The most susceptible to the disease of poliomyelitis are children aged 3 months to 2 years who have not yet sufficiently formed immunity. The highest incidence of poliomyelitis is preserved in countries with hot humid climates (South-East Africa, Asia, India, Armenia, Azerbaijan, Bulgaria, Turkey). Polio is characterized by seasonality with an increase in the incidence rate in the spring-summer period. After infection, persistent type-specific immunity remains.
Mechanism of development of the disease
Entrance gates of infection are the mucous membranes of the pharynx and intestines. After the penetration of the polio virus into the body begins its development, in which there are 4 phases:
- Enteric phase - primary reproduction occurs (replication) of viral particles in the cells of the intestinal mucosa (enterocytes).
- Lymphogenous phase - the virus from the cells of the intestine and pharynx penetrates into the mesenteric lymph nodes or lymphoid tissue, where its replication continues.
- Viremia is 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 the cells of the liver, spleen, lungs, heart, bone marrow. In the cells of these organs, further replication occurs and the repeated release of viral particles into the blood (secondary viraemia).
- The neural phase is the transition 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. In the future, the area of dead nerve cells is replaced by connective tissue.
The severity and localization of paralysis (lack of movement in skeletal muscles due to damage to the motor neurocytes) depends on the number of viral particles and their preferential location in the organs of the central nervous system.
The incubation period for poliomyelitis lasts 7-12 days (there are known cases of a longer incubation period of up to 35 days). Depending on which groups of symptoms prevail in the clinical course of poliomyelitis, there are several main forms of it:
- Typical form with damage to the central nervous system (non-paralytic and paralytic).
- Atypical form (erased or asymptomatic).
Also, the clinical picture of poliomyelitis is characterized by severity, emit mild, moderate and severe course.
Symptoms of a typical paralytic form
The clinical symptoms of this form of polio are characterized by several periods that follow one after another:
- The preparative period - lasts from the onset of manifestations of the first clinical symptoms after the incubation period to the development of paralysis, on average it takes a period of time from 1 to 6 days. During this period, symptoms of general intoxication develop (associated with the release of viral particles into the bloodstream) - an increase in body temperature of up to 38º C and higher, headache and aching muscles and joints. Also joins abdominal pain, vomiting and diarrhea. The pain in the striated muscles appears and increases.
- Paralytic period - characterized by rapid, within 24-36 hours, the development of paralysis (paresis) of certain 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, then paralysis of the legs or arms on one side develops (spinal form). With the localization of a viral infection of the motor neurons of the cranial nerves, paresis of the muscles of the face and soft palate develops, with the appearance of a nasal voice and the impossibility of normal swallowing of food. There are cases of isolated lesion of the neurocyte of the motor nucleus of the facial nerve, in which the paralysis of the facial muscles with asymmetry of the face, incomplete closing of the mouth and eyes develops.
- The recovery period (convalescence) - as the body is freed from the virus and the motor function of neurocytes is restored, there is a gradual recovery of muscles, movements in them and volume.
- Residual period (period of residual effects) - this period is the longest, characterized by residual phenomena in the form of muscle contracture, spinal deformity, muscular atrophy, flaccid paralysis. Such phenomena can remain with the ill person throughout his life.
Symptoms of a typical non-paralytic form
This clinical form is characterized by a sharp onset of the disease with fever and symptoms of general intoxication. Then, over several days, symptoms of irritation of the lining of the brain join - severe headache, hypersensitivity to the auditory (hyperacusia) and visual (photophobia) irritants, stiff neck (their resistance when trying to tilt the head forward). This clinical form is favorable due to the absence of skeletal muscle paralysis. Within 2 weeks, all symptoms gradually disappear.
Symptoms of atypical forms
The course of atypical polio can be blurred and asymptomatic. The erased course is characterized by the appearance of several symptoms at the end of the incubation period:
- Acute onset with manifestations of general intoxication and fever.
- Dyspeptic syndrome - abdominal distension, diarrhea, abdominal pain, loss of appetite.
- Autonomic dysfunction syndrome - a decrease in a person's motor activity (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 the infection corresponds to the period of release of the virus into the blood. In the future, there is a reverse development of symptoms without the formation of paralysis. For an asymptomatic course is characterized by the 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 research.
Epidemiological data and characteristic clinical symptoms allow suspecting the development of poliomyelitis. The final diagnosis is made on the basis of virus isolation or antibodies to it using laboratory diagnostics, which includes:
- Determining the presence of poliomyelitis virus in the feces or cerebrospinal fluid using polymerase chain reaction (PCR).
- Enzyme-linked immunosorbent assay (ELISA) for the rapid diagnosis and detection of viral RNA.
- Serological examination of blood plasma, which allows to detect antibodies to the poliomyelitis virus.
Also, in addition to assessing structural changes in the motor centers of the brain and spinal cord, a clinical analysis of the cerebrospinal fluid and computed or magnetic resonance imaging are performed.
Regardless of the severity and severity of clinical symptoms, if you suspect the presence of polio, hospitalization is required. The regimen during therapeutic measures is only bed rest, the diet includes vitamins, proteins and carbohydrates, with sufficient caloric intake, it should be easily digestible. Therapeutic measures include drug etiotropic and pathogenetic treatment.
To date, effective drugs and drugs that destroy the virus, no. In the early stages of the disease, at the time of active replication of the virus, preparations based on recombinant interferons (reaferon, viferon) are used, which suppress the assembly of viral particles inside the cell.
Treatment is aimed at reducing the severity of inflammation in the organs of the central nervous system (nonsteroidal anti-inflammatory drugs), reducing swelling of the brain and spinal cord (diuretics), restoring neurocytes (neuroprotectors), and using vitamins. Also, physiotherapy is used to improve the motor function of paralyzed muscles, including mud baths, paraffin baths, magnetic therapy.
Vaccination is used to prevent the development of poliomyelitis, 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-lasting stable immunity. To this end, in most countries of the world, polio vaccination is included in the mandatory vaccination schedule. Modern vaccines are polyvalent - they contain all 3 serological groups of the polio virus.
The outcome of a polio disease depends on its form and severity. After a paralytic form, residual effects may remain in the form of flaccid paralysis and muscle atrophy. The relevance of this infection remains high today. In countries with a warm and humid climate, polio outbreaks among children are periodically recorded.
- Measles in adults: photo, symptoms, treatment, prevention
- Brucellosis: symptoms, diagnosis, treatment of brucellosis
- Rubella in adults: photo, symptoms, treatment, prevention