Western Neil's fever

Description:

The Western Neil's fever - an acute viral zooantroponozny prirodnoochagovy disease, with the transmissible mechanism of transfer, characterized by a polyadenopathy, an erythema and an inflammation of the meningeal covers proceeding against the background of a feverish intoksikatsionnogo of a syndrome.

The first epidemic flash was registered in 1937 at a research of the Japanese encephalitis. In the middle of the 20th century one more epidvspyshka in Africa and Asia was registered, is later in the countries of the Mediterranean (especially in Israel and Egypt), the Southern part of Russia, in Belarus, in Ukraine, Romania, the Czech Republic and Italy. Further the serological research confirming existence of antibodies to a virus – in Krasnodar Krai, the Omsk and Volgograd regions was conducted, in Belarus, Azerbaijan, Tajikistan and Ukraine – these researches raise a question of endemicity of territories and transferrings of a disease confirm the fact even if in the erased / subclinical form. Relevance of this disease increased in 1999-2003 when incidence began to increase in the Astrakhan region, Volgograd and Krasnodar Krai.

Reasons of fever of the Western Neil:

The causative agent of fever of the western Nile - флавивирус groups In families of togavirus, the sizes - 20-30 nanometers, contains RNA, has spherical shape. Well remains in the frozen and dried up state. Perishes at a temperature above 56 °C within 30 min. It is inactivated by ether and dezoksikholaty. Has the hemagglutinating properties.

Carriers of a virus are mosquitoes, ixodic and argasovy mites, and an infection tank - birds and rodents. The western Neil's fever has clear seasonality - late summer and fall. More often people of young age get sick.

The risk of a disease above at people is more senior than 50 years. The probability of emergence of serious symptoms of LZN in a case above at people is more senior than 50 years, and they should be careful of mosquito stings especially.

Being on air, you are exposed to risk. The you spend on air more time, the duration of time during which the infected mosquito can bite you is more. If in connection with work or rest you spend much time in the open air, watch that you were not bitten by mosquitoes.

The risk of a disease as a result of the medical procedure is very low. Before use all donor blood is checked for presence of the LZN virus. The risk to catch LZN through hemotransfusion or organ transplantation is very low so people for whom operation is necessary should not refuse it because of this risk. If something disturbs you, talk to the doctor.

Pregnancy and feeding by a breast does not increase risk of infection with fever of the western Nile. Researchers did not come to a final conclusion concerning what risk presents to LZN for a fruit or the baby who catches through mother's milk. In case of concern talk to the doctor or the nurse.

Symptoms of fever of the Western Neil:

Incubation interval – time from the beginning of implementation of the activator, to the first clinical symptoms and, in this case it lasts 3-8 days on average, but can last also up to 3 weeks. During this period the activator passes the way from the moment of a sting of a mosquito, with the subsequent reproduction of the activator in the place of a sting, the bacteremia developing further and primary replication in an endothelium of vessels and bodies of SMF (system of monocytic phagocytes – everything that carry to these bodies is described above).

As soon as the activator reaches a certain concentration and leaves from these target organs where there was primary reproduction replication, there is secondary bacteremia and it marks the beginning of visible symptoms. The period of clinical manifestations – as soon as begins secondary bacteremia, there is an acute beginning from rise in temperature to 38,5-40 °C and it increases within several hours, being followed by obshcheintoksikatsionny symptoms in a look: a fever, a headache localized more often in a forehead, pain in eyeglobes, vomiting, a generalized  mialgiya (muscle pain is especially notable in a neck and a waist), an arthralgia (joint pain) and a febricula.

Outward of the patient reminds hemorrhagic fever  - face reddening, conjunctivitis, an injetsirovannost of vessels of scleras, reddening and granularity of mucous cheeks and a hard palate. The further stage of symptomatology will depend on a type of the striking strain (but anyway the following target organs most often are surprised: liver, brain, kidneys):

• At defeat by "old" strains (i.e. those that were widespread till 90th years) arises: sclerite, conjunctivitis, pharyngitis, polyadenopathy, rash, hepatolienal syndrome, dispepsichesky frustration. But at these strains a current high-quality.

• At infection with "new strains" the further picture of development can be slightly more sad, and thus clinical manifestations are more variable and connected with various forms of this disease:

  - At  a subclinical form there are no clinical manifestations, diagnosis is possible only by means of a screening research – definitions of IgM or increase of a caption of IgG in 4 and more times.
  
- The Grippopodobny form is least studied, т.к people often do not see a doctor because of nonspecific symptomatology, referring to cold. But as soon as the general state worsens, nobody connects it with the previous symptoms. At this form the aggravation of symptoms is registered for 3-5 day and is shown in the form of strengthening of a headache, emergence of nausea and vomiting, a tremor, an ataxy, dizziness, radicular pains, skin hyperesthesias, meningivlny symptoms, long fever – steadily high temperature which keeps about 10 days. This symptom complex is characteristic more of new strains.

  - The Meningialny form is characterized by an exit to the first place of all-brain symptoms (a headache, dizziness, the block, vomiting which is not giving relief, a muscular tremor), the focal symptomatology – an anizorefleksiya, a nystagmus, pyramidal signs also joins this clinic.

  - The Meningoentsefalny form – the most severe form of a disease, т.к  all-brain symptoms proceed is more expressed with gradual increase: confusion of consciousness, excitement, the nonsense, a sopor which is often passing into a coma. Also not on the last place focal symptomatology: spasms, paresis of cranial nerves, nystagmus, paresis of extremities, respiratory frustration, central disturbances of a hemodynamics. At this form the lethality reaches 50%, and at recovered register frequent complications in the form of paresis, muscular tremors and a long adynamy.

Diagnosis:

The diagnosis and the differential diagnosis is based on clinical, epidemiological and datas of laboratory. The main clinical signs are: acute beginning of a disease, rather short feverish period, serous meningitis, systemic lesion of mucous membranes, lymph nodes, bodies of reticuloendothelial system and heart. Rash can seldom be observed.

Epidemiological premises can be stay in the area, endemic on the western Neil's fever, - North and East Africa, the Mediterranean, the southern regions of our country, data on stings of mosquitoes or mites in the specified regions.

The general blood tests and urine, as a rule, do not reveal pathological changes. The leukopenia, at 30% of patients number of leukocytes less 4-109/l can be observed. In liquor - a lymphocytic pleocytosis (100-200 cells), the normal or insignificant increased protein content. Laboratory interpretation is provided with serological tests of RTGA, RSK and RN by method of pair serums. However as many flavivirusa possess a close antigenic affinity, identification in blood sera of antibodies to one of them can be caused by circulation of other virus. The most authentic proof of existence of the infection caused by the western Neil's virus is detection of the activator. From the patient's blood the virus is allocated in culture of cells of MK-2 and on mice weighing 6-8 g (intracerebral infection). Identification of the activator is carried out by a direct method of fluorescent antibodies with use of species-specific lyuministsi-ruyushchy immunoglobulin to the western Nile virus.

Differential diagnosis should be carried out with other arboviral infections, mycoplasmosis, an ornithosis, listerellosis, a toxoplasmosis, tuberculosis, a rickettsiosis, syphilis, flu and other acute respiratory diseases, an enteroviral infection, an acute lymphocytic choriomeningitis.

Treatment of fever of the Western Neil:

T.k all viral diseases are treated by virioidny drugs, the Western Neil's fever did not become an exception, but any of antiviral drugs did not give the expected result and, at the moment treatment comes down only to stopping of symptoms:

1) With a high intracranial pressure – furosemide with drugs of potassium or верошпирон (he acts more slowly in comparison with furosemide, but potassium saving is).
2) At brain hypostasis – Mannitolum with the subsequent administration of furosemide. If swelled a brain fast-progressing, in addition appoint dexamethasone.
3) Compensation of volume of liquid – appoint intravenous infusions of polyionic solutions (трисоль) and colloidal solutions (albumine, реополиглюкин) – 2:1
4) For fight against a hypoxia appoint oxygen inhalations and transfer to IVL according to the following indications:

  • an asthma (the respiration rate increases twice and more from norm);
  • a hypoxia (portion pressure About ₂<70 мм рт ст);
  • a hypocapny (pressure WITH ₂<25 мм рт ст);
  • a hypercapnia (WITH ₂> 45 mm of mercury), generalized spasms or a coma.

5) At spasms appoint Relanium (Seduxenum)
6) Sedative and antioxidants
7) The means improving a brain blood stream (pentoxyfelinines)
8) An antibioticotherapia at consecutive bacterial infections, also appoint the balanced enteral and parenteral food, a complex of vitamins and microelements.

Duration of treatment averages 10 days, at a complication from TsNS – up to 30 days and, only on the expiration of these terms carry out an extract of patients (taking into account the normal temperature and regress of neurologic symptomatology). After an extract from a hospital appoint dispensary observation the neurologist to a complete recovery of working capacity and regress of neurologic symptoms.

Prevention:

Prevention generally nonspecific is also directed to decrease in number of mosquitoes that is reached by carrying out antimosquito processings of places of breeding of mosquitoes in a city part and in nearby territories and territories of rest. Disinsections subject cellars of houses and public buildings in city and rural areas. Consider artificial decrease in population of synanthropic birds (crows, pigeons, sparrows etc.). In the period of seasonality apply the clothes protecting from stings of mosquitoes carrying out time is minimized in the open air.