Encephalitis is an inflammation of the brain. Encephalitides are divided into primary, caused by different neurotropic viruses, and secondary, complicating the overall infectious diseases (varicella, measles, rubella, malaria, influenza, rheumatism, sepsis).

Encephalitis (from the Greek. enkephalos - brain) is an inflammation of the brain. If you are involved in the process and spinal cord used the term "encephalomyelitis".

Etiology encephalitis diverse: infection, intoxication, trauma.
There are primary and secondary encephalitis, characterized mainly by the dynamics of development of pathological process. At primary encephalitis encephalitides syndrome primary and dominant in clinical-anatomical picture, when secondary he complicates the overall infectious disease or local infectious process. Encephalitis when this occurs due to the penetration of the pathogen from the blood or inflammatory focus in the internal organs in the Central nervous system.
In most cases, the primary cause encephalitis specific viruses. Etiological factors of secondary encephalitis are other viruses (encephalitis with influenza, measles, rubella, and so on), bacteria, protozoa (encephalitis malaria, toxoplasmosis), Rickettsia (subnational encephalitis) and spirochetes (syphilis encephalitis).
A special group comprises the so-called postvaccine encephalitides that sometimes occurs soon after vaccination against smallpox, rabies and tick-borne encephalitis.
Primary viral encephalitis include vernal (spring-summer) and the so-called mosquito encephalitis: Japanese, American type St. Louis, the valley of the river Murray (Australian X-disease), American horse encephalomyelitis (Western, Eastern and Venezuelan), etc. it also includes the epidemic (lethargy) encephalitis type Economo. Except the last, viral encephalitides apply arthropods (see Arboviral infections) and characterized by a number of common features. The pathogens of viral encephalitis are arboviruses. They have a size of 15-40 MMK and are characterized by content RNA, sensitive to salts of bilious acids and air, the ability to multiply in the body arthropod vectors.
The causative agent of tick-borne encephalitis allocated in 1937 (L. A. Zilber, E. N. Levkovich, A. K. Shubladze, M. P. Chumakov, V. D. Solov'ev and A. D. sheboldaeva). Currently, the number of known viruses that are close but not identical to the tick-borne encephalitis virus with which they form a separate subgroup in a group In arboviruses. Viruses in this category are the similarities and some differences in antigenic structure and cause diseases with different clinical and epidemiological features (Omsk hemorrhagic fever, Scottish encephalomyelitis sheep, kazanetsky forest disease). Each of the pathogen of this subgroup are considered as independent species. On the territory of the USSR detected new variant of tick-borne encephalitis - a two meningoencephalitis, the agent which is very close to the virus of tick-borne encephalitis. Some researchers identify both virus, others consider a virus of a two-meningoencephalitis as independent species. The viral etiology of Japanese encephalitis installed Hayashi (N. Hayashi) in 1933, In the USSR the causative agent of Japanese encephalitis allocated in 1939 A. A. Smorodintseva, A. K. Shubladze and B. D. Neustroevy.
Pathogens encephalitis similar stability in the external environment to the action of different factors, but also by the ability to be cultivated in chicken embryos and tissue culture. In the part of the brain, located in 50% solution of the neutral glycerine at temperature 5 degrees, the virus can survive for many months, and in lyophilised - for many years. When temperature 56-60° they die in 10-30 minutes Optimal for the preservation of these viruses is pH=7,0-8,0. Installed
their photodynamic inactivation. Under the influence of ultraviolet rays, depending on the nature of vaccinated material they are inactivated through 15-40 min Virus of a two-meningoencephalitis in cow's milk can survive at temperature 4 degrees and in two weeks, and in sour cream and butter - within 2 months. Complete inactivation of virus in milk occurs at 72 degrees per 10 seconds.
Of disinfectant most rapid disinfecting effect on viruses has Lysol, which at 1% concentration kills the virus of tick-borne Japanese encephalitis in 20 minutes Significantly slower act formaldehyde and phenol.
From laboratory animals to cause encephalitis most susceptible white mouse, especially the kids. Viruses reproduce in chicken embryos and different types of tissue cultures, have hemagglutination properties. For the reaction of haemagglutination is mainly used with goose red blood cells.
The main feature characterizing pathogens encephalitis is their affinity to the nervous tissue - neurotropism. In a study of people who died from encephalitis, the greatest concentration of virus is discovered in the brain. The blood, spinal fluid and parenchymatous organs contain the virus fickle and in relatively small quantities. The virus in the organism spreads hematogenous route. Wirusami in animals has a large epidemiological significance because promotes the dissemination of the virus arthropods.
Viral encephalitides leave a lasting and strong immune system. In blood convalescent people find specific antibodies detectable in neutralization reactions, of complement fixation and haemagglutination inhibition. In blood of patients antibodies persist for many years. Antibodies detect not only we recover and vaccinated, but also in people, long-living in natural foci of encephalitis.

Primary encephalitis

Primary encephalitis include encephalitis, lethargic epidemic encephalitis, Economo, Japanese mosquito encephalitis, Australian mosquito encephalitis, American mosquito encephalitis type St. Louis, parrot encephalitis virus etiology, a two spring-summer encephalitis, Scottish tick-borne encephalitis, hemorrhagic encephalitis type Strumpell - Leichtenstein, herpes encephalitis. The most common tick-borne encephalitis.
Pathogens encephalitis similar to each other in relation to the impact of various factors and preservation of viability. Viruses are easily destroyed from exposure to disinfectants in normal concentrations. In 50% glycerin solution or dried in vacuum in the cold, they can remain viable from a few weeks to several years, heating up to temperature 56-60° kills them within 10-25 minutes When exposed to ultraviolet rays viruses are inactivated through 15-40 min
Epidemiology. Primary encephalitis - infectious diseases; it may cause epidemics. Carry viruses primary encephalitis are mosquitoes (see), ticks (see), Pets allowed. Characterized by a strong seasonality of diseases and endemicity, which is determined by the biological characteristics of the vector (see Natural focality).
On the territory of the USSR are found tick-borne encephalitis, mosquito (Japanese encephalitis, a two spring-summer encephalitis.
The reservoir of infection with tick-borne encephalitis are different types of small rodents and birds (thrushes, hazel grouse), living in a wooded area, vector - ticks. The pathogen enters the body through the bite of an infected tick. The disease is registered mainly in may - July, mainly in the taiga areas of the Khabarovsk and Primorsky territories, and also in Western Siberia, Urals, North-Eastern areas of the European part of the USSR, Belarus and Western Ukraine. The incubation period is 7 to 21 days, usually 10 to 14 days. Sick people of all ages, mostly men, working in the taiga.
The source of infection with Japanese mosquito encephalitis are birds, horses, pigs; vector mosquitoes of the genus Culex. The pathogen enters the body of a person by the bite of a mosquito. In the USSR the disease is registered in the Primorsky region, primarily in August - October. The incidence often marked among rural residents (about 70% of all cases). The incubation period is 4-21 day. After the disease remains a strong immunity, re disease is not observed.
The source of infection in a two spring-summer meningoencephalitis is cattle, goats, sheep, dogs. Most epidemiological significance are infected goats, as the virus is transmitted from them through raw milk. In this regard, often recorded outbreaks of the disease in families, primarily in rural areas. The disease is benign.
An important role in morbidity plays sensitivity and reactivity of organism of man. Primary encephalitis can be acute or chronic, can result in complete recovery or leave different consequences.