Japanese encephalitis is an infectious disease that affects not only humans but also animals. The virus mainly infects the brain. Endemic outbreaks are observed from August to September and last no more than 50 days a year. The appearance of heavy rainfall against the background of hot weather is a beneficial environment for the reproduction of pathology carriers - mosquitoes.
A bit of history
As far back as 1871, Japanese doctors described a disease with a fatal outcome in 60% of cases. As early as 1933, Hayashi isolated the virus and established exactly how the disease was transmitted. On the territory of Russia, the first mention of the Japanese encephalitis virus appeared in 1938, the disease was discovered in South Primorye.
The virus got its name from an outbreak in Japan. In those terrible times, namely in 1924, more than 7 thousand people were affected by the virus, 80% of all patients died.
In our country, the disease is also called encephalitis B, mosquito or summer-autumn encephalitis.
Etiology and microbiology of Japanese encephalitis
The causative agent of the disease is a virus of the genus Flavivirus, from the family Togaviridae. The virus dies when heatedtemperatures up to 56 degrees in only 30 minutes. If you boil it, it will die in 2 minutes. If the virus is dried and frozen, it will not die and can be stored almost forever. At room temperature, the virus can survive for about 45 days, and in a dairy environment up to 30 days.
Possible vectors
Under natural conditions, waterfowl are the main carrier. Some rodents have also isolated the virus.
In part-time farms, pigs and horses can act as carriers of Japanese encephalitis. Pigs carry the disease asymptomatically, and the incubation period is not more than 5 days. Very rarely, sick pigs may have spontaneous abortions.
An infected person is dangerous to others. The virus enters the human body through the saliva of infected mosquitoes. In humans, the incubation period ranges from 4 to 21 days. The accumulation of infection occurs in the nervous tissue of various parts of the brain. Possible vascular lesions of the membrane and tissue of the brain. At the same time, most often the pathology is asymptomatic. Most people who have never had encephalitis have antibodies in their bloodstream. With age, each person's immunity only strengthens.
Where is the virus most common?
Naturally, Japanese encephalitis is not very typical for the territory of our country. The virus is found from south to southeast Asia, this is the northern part of Australia, India, Pakistan, Thailand, Japan and Indonesia. In the list of "dangerous" countriesincludes about 24 states. In general, about 3 billion inhabitants of the planet live under the threat of the appearance of the disease. On the territory of our country, mosquitoes that can cause disease are found in abandoned villages, on the outskirts of villages and cities, in areas where it often rains and high humidity.
Pathogenesis
The nature of the course of Japanese encephalitis depends on the general state of he alth. The he althier a person is, the lower the risk of getting sick. Most often, the virus dies already at the injection site.
If, nevertheless, the virus “lingers” in the body, then its development depends largely on body temperature: if it rises, then the virus “rages” and develops rapidly. Elevated human body temperature contributes to the intensive course of the disease. Once the virus has crossed the blood-brain barrier, it travels to the brain parenchyma. It is in this place that the active development of the virus begins. In severe cases, reproduction may begin already in the nervous system.
Japanese encephalitis symptoms
In humans, the disease occurs in three periods:
1. Elementary. The duration of the period is about 3 days. It is characterized by a spontaneous increase in body temperature up to 40 ° C, which can last at this level for about 10 days. A person is worried about headache, chills, pain in the lumbar region, gastrointestinal tract, and in the limbs. Some patients experience nausea, up to vomiting. The pressure may increase and the pulse quickens up to 140 beats.
2. acute period. On the 3rd or 4th day comesexacerbation of the pathology, signs characteristic of meningitis may appear, the patient's condition is depressed, up to coma. Many patients suffer from mental disorders, hallucinations, delusions.
Muscle tone increases, and the patient can only be in a supine position, on his side or on his back. The limbs are in a bent state. Muscle spasms are observed on the occipital and masticatory muscles. Possible hyperemia of the optic nerve, up to edema. Some patients have pneumonia or bronchitis.
3. convalescence period. Japanese encephalitis at this stage can progress up to 7 weeks. Body temperature usually stabilizes and returns to normal. There may be residual effects of brain damage, muscle weakness, lack of coordination, bedsores.
There are patients who have a mild illness without neurological symptoms.
Severe disease can lead to death.
Features of epidemiology and prognosis
The causative agents of Japanese encephalitis are most often found in sparsely populated areas, near water bodies and swamps. In tropical countries, epidemics last longer than 50 days. The risk group includes people who work outdoors or near water bodies. Most often, Japanese encephalitis affects men from 20 to 40 years old.
At risk are also tourists who go on vacation to countries with a tropical climate, where there are monsoons and high humidity. This is the Philippines, Thailand, in particularnorthern part of the state, India, Indonesia and other countries. Therefore, tourists are strongly advised to be vaccinated before traveling to hot countries.
Prognosis for recovery is very small, the probability of death reaches 80%. As a rule, the first 7 days are dangerous, the patient may fall into a coma, or he is tormented by endless convulsive attacks.
People who have gone through all stages of the disease often have residual effects:
- psychosis;
- hyperkinesis;
- intellectual decline;
- paralysis;
- asthenic condition.
Diagnostic measures
Diagnosing a disease is a whole complex of clinical and laboratory studies. When choosing a method, doctors are guided primarily by the patient's condition. Diagnosis includes:
1. Laboratory research. In the first week after infection, pathology can be determined by a blood test. Over the next two weeks, the diagnosis of the disease can be based on the results of studies of cerebrospinal fluid.
2. Serological study. Diagnosis involves the use of enzyme immunoassay or RN-, RNGA-, RTGA- and RSK-tests.
Treatment measures
Treatment of patients who "met" carriers of Japanese encephalitis cannot be carried out by only one doctor. Therapy includes infectious disease specialists, neurologists and resuscitators. ATin stationary conditions, the patient is injected with a specific immunoglobulin or serum, about 3 times a day for 1 week of treatment. Along with this, symptomatic and pathogenetic therapy is carried out. These activities are aimed at preventing cerebral edema, detoxification, normalization of the activity of all organs and systems.
The main problem is that there is no cure for Japanese encephalitis. Therapy can only eliminate the symptoms. Therefore, it is very important to vaccinate in a timely manner.
Prevention of disease
To prevent epidemics, active immunization of the population is very important. Vaccinations against Japanese encephalitis are called "formolvaccine". Passive emergency prophylaxis involves the administration of 6 ml of immunoglobulin and 10 ml of hyperimmune horse serum.
Besides this, the prevention of morbidity is a series of comprehensive measures to protect against mosquito attacks. In epidemiologically dangerous areas, the use of protective clothing may be recommended. Mandatory to use repellents, from ointments to sprays, the use of all measures to prevent mosquitoes from entering the living quarters.
You can get vaccinated against Japanese encephalitis in Moscow at municipal and private medical institutions.
Most often a person is vaccinated with a “killed” vaccine, so there are no complications after vaccination. At the same time, it is recommended to consult a doctor if allergic reactions occur. You may experience redness and swelling at the injection site. Headache, diarrhea, pain in the muscles may appear. Some patients complain of dizziness and nausea, chills and rashes.
Immunization is not carried out in the presence of a number of infectious diseases, during gestation and lactation, if it is known for sure that the patient has hypersensitivity to heterologous proteins, severe allergic reactions.
Today, there are 4 main types of Japanese encephalitis vaccines:
- inactivated;
- based on mouse brain cells;
- inactivated, based on Vero cells;
- live recombinant and live attenuated vaccines.
The most popular vaccine, SA14-14-2, has been requalified by WHO and is manufactured in China.
For tourists, vaccination is carried out depending on which country they are going to travel to, where they will live, on the outskirts of the village or in the city, for how long, 1 week, month or year.
Vaccination can be carried out according to two schemes:
| complete | shortened | |
| vaccination days | 1, 7, 30 | 1, 7, 14 |
| vaccination age | from 1 year of life | from 1 year of life |
| revaccination | every 3 years | every 3 years |
Citizens with subsidiary farms should take care of the vaccination of animals,which they grow. For pigs, "live" vaccines are most often used. In areas classified as risk zones, it is advisable to carry out regular treatment with insecticides.
