Zeka virus( Zika fever) - Causes, symptoms and treatment. MF.
Jun 27, 2018
Zika virus or fever Zika virus - zooanthroponotic( transmitted from an animal to a human person) is a natural focal( inhabiting under certain climatic conditions) arbovirus( transmitted by the parasitized insects) infectious disease, with a transmissible mechanism of transmission of the pathogen( through the bites of infected mosquitoes in this case -genus Aedes), characterized by a sudden onset, fever, intoxication syndrome, sometimes hemorrhagic and meningic symptoms, it is possible the icterism of the skin and sclera.
Zicka virus carrier - Aedes genus
Causes of Zeka virus
Pathogen: RNA-containing arbovirus from the Flaviviridae family of the Flavivirus family. The virus of Zika refers to the complex of Uganda, Banzi and Spondveni. In nucleocapsid contains one protein with group-specific antigenic properties and typical specificity - which predetermines the symptoms and peculiarity of the course.
The causative agent of the Zika virus is not very stable in the external environment and is easily inactivated by heating and conventional disinfectants.
But before the influence of destructive factors, the virus has a high rate of reproduction and development of the cytopathic effect( degenerative cell changes) in many cell cultures, including cells carrying macrophage Fc receptors and the lines of these cells( natural killers, neutrophils and mast cells), in which the virus yield rises in the presence of specific antibodies. Ie instead of the supposed elimination of the pathogen in the immune response, there is even greater activation of the virus!
High reproduction rate is also observed in mosquito cell cultures, but without cytoplasmic effect( ie the virus multiplies itself, without destructive effect on the host cells) - it is attached to the cells by the receptor of the glycoprotein E1 and E2, penetrates into the cell by endocytosisand replicates in the cytoplasm, only partially including the nucleic and protein synthesis of mammalian host cells, but does not stop the functioning of arthropods cells.
Infection, thus, is accompanied by the proliferation of perinuclear membranes, i.e., the probation / destruction of large areas and, as a consequence, the violation of many important functions at the cellular level. The above-mentioned E protein induces neutralizing anti-bodies and other structures of protective immunity.
Structure of the virus Zika
When referring to the structure, it is worth remembering the pathogenicity of the pathogen to the cells of bone marrow origin, ie the virus prefers to attack the immune cells.
Counterweight to the danger of the disease:
• rapid attenuation of the pathogen - that is, reduced virulence( infectiousness) with frequent passages, which is explained by high mutation and stabilization of the mutated virus in a specific and homogeneous cell type. In this case, an example is the reduction of neurotropism and viscerotropy - that is, clinical and morphological manifestations will proceed more smoothly in subsequent infected.
But on the other hand, it can lead to a departure from immune control, because the cells of the immune system can not fully recognize the pathogen.
Epidemiology of the Zika virus
The reservoir and source of the pathogens are predominantly mosquitoes of the genus Aedes inhabiting humid climates( the territory of the Left Bank Ukraine) and in countries with a temperate climate( the Black Sea coast of the Caucasus).But so far, for several decades since its discovery, the virus of Zika was recorded in south-west, central and eastern Africa, and also in South-East Asia, but the virus had a sporadic incidence without mass manifestations.
Since 1947, when the virus was discovered and until the present epidemic, which arose in 2015, when the virus acquired a mass character, only a few were sick, and only in the equatorial and tropical zones, the disease proceeded relatively safely and did not cause much concern.
As of the beginning of 2016, the virus had already captured 23 countries and a link was found between the disease and malformations of the fetal nervous system during infection of mothers during pregnancy. So far, the risk of morbidity in Russia has been minimized, due to climatic conditions, but it is impossible to exclude it to the end.
Scheme of the development of the disease from the moment of penetration of the virus into the body:
• After penetrating the skin with a mosquito bite, the virus enters the bloodstream, but initially infects the dendritic cells near the site of implantation.
• Next comes the stage of reproduction, which occurs in the endothelium and reticuloendothelial cells of the lymph nodes, with the Zika virus, the antigens are localized in the nuclei of the affected cells, and not in the cytoplasm. On the basis of the tropicity of reproduction in the blood( in diagnosis), a picture of leukopenia first appears, followed by leukocytosis.
• As a result of tropicity to the cells of RES( reticuloendothelial system), which has a total prevalence, there is a risk of local multiplication of the virus: in the liver, brain, kidneys. Proceeding from this, the symptoms will also unfold: fever, headache, myalgia, arthralgia, small-papular rash, conjunctivitis, icterism of the skin and visible mucous membranes.
• To date, in a significant number of cases, clinical manifestations have been limited to periods of dissemination of viruses, followed by recovery without consequences. Currently, the course has acquired other outlines - with a brighter clinical picture, and more formidable complications: fever may be complicated by hemorrhagic symptoms, as a result of vascular disorders, this manifests itself in the form of hemorrhagic bleeding without a traumatic factor;fever can acquire with a two-wave current, where at the height of the second wave, there are new clinical and laboratory changes( albuminuria, meningic signs, encephalitis, myelitis) speaking in favor of secondary organ damage.
Symptoms of the Zika virus
1. A sudden onset with the predominance of one or more symptoms at the onset of the disease: weakness, headache, fever for up to seven days with a temperature of 39-40 C, small-spot rash, myalgia and arthralgia( pains in muscles and joints), conjunctivitis( inflammation of the eyes), icterus( icterus) of the skin and mucous membranes.
2. The flow of a fever can be two-wave, that is, the temperature after a fall will rise again.
3. Possible secondary organ damage, mediated primarily by viral damage. Depending on the affected organ( s), these or other symptoms appear: cerebral and / or focal neurological symptoms, symptoms of liver and kidney damage, vascular lesions in the form of small-dotted rashes and bleeding.
Diagnosis of the virus Zika
In the priority serological diagnosis of RSK, RTGA, RNIF, ELISA methods;PCR tests in the acute period of the disease or not later than 5 days after it.
Treatment of the disease caused by the virus Zika
Unfortunately, there is no specific treatment for this virus yet, and in the arsenal only symptomatic and pathogenetic, i.e. effect on the symptoms and the main links of pathogenesis.
There is a variant of using immunomodulating and immunostimulating therapy for determining the affected immune link, specific medications are determined by a doctor from common drugs such as Cycloferon, Viferon, Polyoxidonium, Lycopid and others, but there are no clinical recommendations for this time period in the Russian Federation, they are still under development.
When signs of central nervous system damage apply such groups of drugs as diuretics( with intracranial hypertension), dehydration therapy, if necessary - spinal puncture.
In order to prevent secondary bacterial complications, antibiotics of a wide spectrum are prescribed, except for tetracyclines and levomycetin due to adverse effects on blood vessels.
Narrow-spectrum antiviral therapy is under development and depends on the complete collection and analysis of information about the virus.
The disease itself, together with the incubation period, lasts up to 14 days, of which from 3 to 7 days the height with all the symptoms( if they occur, up to 30% of the diseases can be asymptomatic or confused with other diseases), the duration of the disease does not dependfrom treatment, it only facilitates the clinical picture.
Most often( except for pregnant women) does not cause any complications and passes almost completely without a trace with full recovery.
With regard to pregnant women, there is no evidence base for their treatment, and treatment measures often do not prevent complications associated with fetal microcephaly. In many countries, there are recommendations to refrain from the nearest childbearing until the spreading and finding the best treatment are planned, which they plan to develop by the end of 2016 to early 2017 and conduct their clinical trials.
Microcephaly is a malformation of the fetal brain, the disease is a consequence of a violation of migration and differentiation of nerve cells. Microcephaly is characterized by a decrease in the volume of the brain, so that the child develops mental retardation.
In the Russian Federation, the disease and spread of the virus is extremely unlikely due to the peculiarities of our climate in which it is impossible to realize the life cycle of the vector. But episodic diseases are possible due to globalization and the absence of long periods of travel between countries, which may result in isolated cases due to contamination in third countries or the importation of an insect virus.
There is also one confirmed case of sexual transmission of the virus, which can be a serious problem for humanity and have an unfavorable prognosis for the spread of the infection.
Prevention of the Zika virus
Currently, the most important protective measures are combating mosquito populations and preventing mosquito bites among people at risk, especially among pregnant women.
Vaccine prophylaxis is not developed, studies are underway to establish it, many of the countries announced its creation by 2017, including the Russian Federation.
Therapist doctor Shabanova I.Е.