Sinusitis

Incubation period for West Nile fever. Protection against West Nile Virus Starts with Mosquito Control

Synonyms: West Nile encephalitis, West Nile encephalitis; Encephalitis Nili occidentalis - lat.; West-Nile encephalitis

West Nile fever- an acute transmissible viral disease characterized by fever, serous inflammation of the meninges (extremely rare - meningoencephalitis), systemic damage to the mucous membranes, lymphadenopathy and, less commonly, rash.

West Nile fever virus was first isolated from the blood of a sick person in 1937 in Uganda. Subsequently, there were indications of the widespread spread of the disease in Africa and Asia. The disease is most common in Mediterranean countries, especially Israel and Egypt. Cases of the disease have been described in France - on the coast Mediterranean Sea and in Corsica, as well as in India and Indonesia. The existence of natural foci of the disease in the southern regions has been proven former USSR- Armenia, Turkmenistan, Tajikistan, Azerbaijan, Kazakhstan, Moldova, Astrakhan, Odessa, Omsk regions, etc.

Etiology. The causative agent is a flavivirus of group B of the togavirus family, size - 20–30 nm, contains RNA, has a spherical shape. Keeps well frozen and dried. Dies at temperatures above 56°C for 30 minutes. Inactivated by ether and deoxycholate. Has hemagglutinating properties.

The carriers of the virus are mosquitoes, ixodid and argasid ticks, and the reservoir of infection is birds and rodents. West Nile fever has a distinct seasonality - late summer and autumn. Young people get sick more often.

Pathogenesis. The mechanism of infection and the routes of spread of the virus in the human body are the same as with other mosquito encephalitis. However, viremia does not always lead to damage to nervous tissue. There are known cases of latent infection. The pathogen is tropic not only to the cells of the central nervous system, but also to the vascular endothelium; the virus may persist in the human body for a relatively long time (more than 1–2 months).

Symptoms and course. Incubation period ranges from several days to 2–3 weeks (usually 3–6 days). The disease begins acutely with a rapid increase in body temperature to 38–40°C, accompanied by chills. In some patients, an increase in body temperature is preceded by short-term symptoms in the form of general weakness, decreased appetite, fatigue, a feeling of tension in the muscles, especially in the calf muscles, sweating, and headaches. The febrile period lasts on average 5–7 days, although it can be very short – 1–2 days. The temperature curve in typical cases is remitting in nature with periodic chills and excessive sweating, which does not bring patients any improvement in well-being.

The disease is characterized by pronounced symptoms of general intoxication: severe painful headache with predominant localization in the forehead and eye sockets, pain in eyeballs, generalized muscle pain. Particularly severe pain is observed in the muscles of the neck and lower back. Many patients experience moderate pain in the joints of the extremities; there is no swelling of the joints. At the height of intoxication, repeated vomiting often occurs, there is no appetite, pain in the heart area, a feeling of freezing, and others appear. discomfort in the left half chest. Drowsiness may occur.

The skin is usually hyperemic, and sometimes a maculopapular rash can be observed (5% of cases). Rarely, usually with prolonged and undulating fever, the rash can become hemorrhagic. In almost all patients, pronounced hyperemia of the conjunctiva of the eyelids and uniform injection of the vessels of the conjunctiva of the eyeballs are detected. Pressing on the eyeballs is painful. In most patients, hyperemia and granularity of the mucous membranes of the soft and hard palate are determined. However, nasal congestion and dry cough are relatively rare. There is often an increase in peripheral lymph nodes(usually submandibular, anglemaxillary, lateral cervical, axillary and cubital). Lymph nodes are sensitive or slightly painful on palpation (polylymphadenitis).

There is a tendency towards arterial hypotension, muffled heart sounds, a rough systolic murmur may be heard at the apex. The ECG may reveal signs of myocardial hypoxia in the area of the apex and septum, focal changes, and slowing of atrioventricular conduction. Pathological changes in the lungs are usually absent. Very rarely (0.3–0.5%) pneumonia may develop. The tongue is usually covered with a thick grayish-white coating and is dry. Palpation of the abdomen often reveals diffuse pain in the muscles of the anterior abdominal wall. There is a tendency to retain stool. In approximately half of the cases, moderate enlargement and sensitivity are detected on palpation of the liver and spleen. Gastrointestinal disorders may occur (usually enteritis-type diarrhea without abdominal pain).

Against the background of the clinical manifestations described above, it is found syndrome serous meningitis (in 50% of patients). It is characterized by dissociation between mild meningeal symptoms (stiff neck muscles, Kernig's sign, less commonly Brudzinski's symptoms) and distinct inflammatory changes in the cerebrospinal fluid (pleocytosis up to 100–200 cells in 1 μl, 70–90% lymphocytes); a slight increase in protein content is possible. Scattered focal neurological microsymptoms are characteristic (horizontal nystagmus, proboscis reflex, Marinescu-Radovici sign, mild asymmetry palpebral fissures, decreased tendon reflexes, absence of abdominal reflexes, diffuse decrease in muscle tone. Some patients exhibit symptoms of radiculoalgia without signs of prolapse. Encephalitic symptoms themselves are observed extremely rarely, but signs of mixed somato-cerebrogenic asthenia (general weakness, sweating, mental depression, insomnia, weakened memory) persist for a long time.

Diagnosis and differential diagnosis based on clinical, epidemiological and laboratory data. The main clinical signs are: acute onset of the disease, a relatively short febrile period, serous meningitis, systemic damage to the mucous membranes, lymph nodes, organs of the reticuloendothelial system and the heart. Rarely, a rash may occur.

Epidemiological prerequisites may include staying in an area where West Nile fever is endemic - North and East Africa, the Mediterranean, the southern regions of our country, information about mosquito or tick bites in these regions.

General blood and urine tests, as a rule, do not reveal pathological changes. Leukopenia may be observed, in 30% of patients the number of leukocytes is less than 4 10 9 / l. In the cerebrospinal fluid there is lymphocytic pleocytosis (100–200 cells), normal or slightly increased protein content. Laboratory interpretation is provided by serological reactions of RTGA, RSK and RN using the method of paired sera. However, since many flaviviruses have a close antigenic relationship, the detection of antibodies to one of them in blood serum may be due to the circulation of another virus. The most reliable evidence of West Nile virus infection is detection of the pathogen. The virus is isolated from the patient's blood in MK-2 cell culture and in mice weighing 6–8 g (intracerebral infection). Identification of the pathogen is carried out by the direct method of fluorescent antibodies using species-specific luminescent immunoglobulin to West Nile virus.

Differential diagnosis should be carried out with other arboviral infections, mycoplasmosis, psittacosis, listerellosis, toxoplasmosis, tuberculosis, rickettsiosis, syphilis, influenza and other acute respiratory diseases, enterovirus infection, acute lymphocytic choriomeningitis.

Treatment. IN acute period Disease patients require bed rest. They are prescribed vitamins and other restoratives. In cases of severe meningeal syndrome, repeated spinal puncture and steroid hormone therapy are indicated. There is no specific treatment. Pathogenetic and symptomatic therapy is carried out.

Forecast. The disease tends to have an undulating course. 1–2 relapses of the disease may occur (with an interval of several days). The first wave is most often characterized by serous inflammation of the meninges, the second by damage to the heart, and the third by catarrhal phenomena. The course of the disease is benign. Despite prolonged asthenia during the convalescence period, recovery is complete. No residual effects or deaths were observed.

Prevention and measures in the outbreak. Preventive measures are based on mosquito control and protection from their bites.

West Nile fever (WNF) first became known in the late 1930s, when researchers were able to isolate the causative agent of this disease from the blood of a patient. Subsequently, data began to appear about widespread this viral infection among the population of Asia, South America and Africa.

According to statistics, outbreaks of this disease are especially often observed in many Mediterranean countries (in particular in Egypt and Israel). Also in medical literature cases of detection of this viral infection in Indonesia, India and France (Corsica and the Mediterranean coast) are described. Scientists were able to identify outbreaks of this disease in Pakistan, Senegal, Turkmenistan, Moldova, Zaire, Algeria, Nigeria, Azerbaijan, Armenia, Sudan, Tajikistan, Kazakhstan, Ethiopia, Czech Republic, Romania, Omsk, Volgograd, Astrakhan, Odessa region etc. Such an expansion of the nosoarea occurred at the end of the last century. Researchers associate such a spread of the disease from regions with a particularly hot climate to areas with moderate weather conditions with seasonal migrations of wild birds, which are a reservoir of infection.

WN fever is a zooanthroponotic (that is, affecting both people and animals) viral infection, which is acute, transmitted transmissibly (during bites by blood-sucking arthropods) and is accompanied by the occurrence of:

fever;
systemic lesions of the mucous membranes;
serous inflammation of the membranes of the brain (sometimes up to meningoencephalitis);
lymphadenopathy;
in rare (up to 5%) cases, the appearance of a skin rash.

Not only people, but also mammals can be infected. According to statistics, this disease is more often detected among people whose professions are related to agriculture, or rural residents. Also increased risk infection is observed among hunters, fishermen and others who spend a lot of time in the favorite places of arthropods (for example, near water bodies).

As a rule, outbreaks of infection are observed in early spring or in the summer-autumn period. The peak incidence - more than 90% of all identified outbreaks - is recorded from July to October, when the number of blood-sucking insects reaches its maximum.

In the literature you can find other names for what is being considered in this article. viral disease:

West Nile fever;
MN encephalitis;
duck fever.

In some cases, this infection can cause complications that are dangerous to health and life, such as cerebral edema, which can subsequently cause coma and death of the patient. Not only residents of endemic dangerous regions, but also tourists who are going to visit these geographical areas should know about it. You can get information about the causes, symptoms, methods of diagnosis and treatment of West Nile fever in this article.

Characteristics of the infectious agent and routes of its transmission

This pathology is viral in nature. The pathogen enters the human body through the bite of a blood-sucking insect.

The development of WN fever is provoked by the invasion of the body by an RNA-containing flavovirus of group B. It has a spherical shape and dimensions of 20-30 nm.

Natural susceptibility to infection with WN fever virus is high, and after past infection Those who have recovered develop intense or persistent immunity.

How does the infection develop?

After entering the blood, the virus, along with its current, spreads throughout the body, causing systemic lesions:

First of all it suffers lymphoid tissue and as a result, the patient exhibits lymphadenopathy.
If the infectious agent penetrates the blood-brain barrier, then the infected person may develop damage to the substance and membranes of the brain (up to).

In some cases, infection leads to the death of the patient.

Symptoms

In some cases, after infection with the pathogen of WN fever, the patient does not develop any symptoms, but in others, after 3-14 days (sometimes after 3 weeks), the patient develops signs of this viral disease. According to statistics and WHO, asymptomatic of this disease is observed in 80% of cases, and the manifest form of ZN fever proceeds typically and with the development of violent symptoms.

In the manifest course, the disease manifests itself in two variants:

without CNS lesions - accompanied flu-like symptoms(sometimes with the addition of neurotoxicosis);
with damage to the central nervous system - accompanied by meningeal or meningoencephalitic manifestations.

Whenever clinical symptoms signs of infection usually occur acutely, and the viral infection manifests itself with an increase in temperature to high numbers (38-40 ° C). The febrile period is accompanied by chills.

Often, before the onset of a fever, the following symptoms are felt:

severe weakness;
loss of appetite;
a feeling of tension in the muscles (usually the calf muscles);
headaches.

The duration of the increase in temperature usually ranges from 5 to 7 days (sometimes 1-2 days). ZN fever is characterized by a remitting course of a febrile period with periodic chills and heavy sweating.

In addition to fever, patients show signs of intoxication:

frequent and strong, localized in the area of the eye sockets and forehead;
myalgia (especially intense in the neck and lower back);
pain in the eyes;
mild arthralgia without swelling of the skin over the articular joint.

At the peak of the development of intoxication syndrome, the patient experiences the following symptoms:

repeated vomiting;
reluctance to eat;
chest discomfort and heart pain;
sensations of heart sinking;
drowsiness.

The skin of patients becomes hyperemic, and about 5% of them develop small papular rashes. IN in rare cases, with a long and undulating course of the febrile period, such elements of the rash can transform into hemorrhagic ones.

Almost all infected people experience redness of the conjunctiva and injection of the blood vessels of the eyeballs, and pain is felt when pressing on the eyes.

Many patients have enlarged lymph nodes. As a rule, in pathological process involved:

submandibular;
lateral cervical;
Anglomaxillary;
cubital;
axillary lymph nodes.

When palpated, they are sensitive or slightly painful.

Sometimes infected people experience nasal congestion and a dry cough. When examining the oral cavity, granularity and redness of the mucous membranes of the hard and soft palate are revealed.

The following changes are detected in the heart and blood vessels:

tendency to;
muffled heart sounds;
heard at the apex of the heart rough systolic murmur(Sometimes);
for: focal disorders, manifestations of hypoxia of the heart muscle, slowdown of atrioventricular conduction.

During examination, the doctor may detect following symptoms:

thick gray-white coating on the tongue;
dry tongue;
diffuse pain when palpating the anterior wall of the abdomen;
moderate sensitivity and enlargement of organs determined by palpation of the spleen and liver;
without painful sensations in the stomach.

When the pathogen penetrates the blood-brain barrier, which is observed in approximately 50% of cases, the patient, against the background of the above-described manifestations, develops following signs serous meningitis:

increased tone of the neck muscles (that is, their rigidity);
Kernig's sign;
Brudzinski's symptoms;
signs inflammatory processes in the cerebrospinal fluid (lymphocytes up to 70-90%, pleocytosis up to 100-200 cells in 1 μl);
horizontal nystagmus;
asymmetry of the palpebral fissures (in mild degree);
decreased tendon reflexes;
proboscis reflex;
decreased muscle tone;
lack of abdominal reflexes.

Encephalitic manifestations of MN fever are detected in very rare cases, but residual signs of asthenia of a mixed nature, manifested in weakness, increased sweating, memory impairment, sleep disturbances and mental depression, persist for a long time.

Flu-like form

The influenza-like form of the disease is characterized by fever, sore throat, sneezing and cough.

With this course of infection, signs of fever (for several days), weakness, eye pain and chills are detected. In some cases, patients complain of cough and discomfort (soreness, soreness) in the throat.

Upon examination, the following signs are determined:

redness of the back of the pharynx and palatine arches;
scleritis

In some cases, signs of indigestion may occur:

diarrhea;
nausea;
vomit;
stomach ache;
and (not always).

Typically, a flu-like course occurs as a viral infection and is often accompanied by signs of meningism.

Neuroinfectious form

This form of the disease is observed in most clinical cases. With this course of MN fever, the patient exhibits the following symptoms:

temperature increased to 38-40 °C (for 7-10 days or several weeks), accompanied by chills;
sweating;
nausea and vomiting (up to 5 times a day), which is not associated with food intake;
headaches;
lower back pain (not always);
myalgia (not always).

In more rare cases, symptoms of meningism, serous meningitis, and in extremely rare cases, meningoencephalitis are observed. After the patients’ condition improves, they continue to have the following residual neurological manifestations for a long time:

weakness;
apathy;
memory impairment;
sleep disorders.

Exanthematous form

This form of infection is extremely rare. On days 2-4, the patient develops elements of maculopapular (less commonly roseola-like or scarlet-like) polymorphic exanthema. Against the background of these manifestations there is:

feverish condition;
catarrhal disorders;
intoxication syndrome.

The rashes disappear after a few days and no pigmentation remains on the skin after the rash. Often, with this form of MN fever, the patient's lymph nodes become enlarged. They can be moderately painful when trying to palpate or make movements.

Character of the current

According to specialists, this infection is asymptomatic in 80% of cases. Mild signs of infection by the virus occur in 20% of those infected. They usually have the following symptoms:

headaches;
fever;
vomit;
nausea;
enlarged lymph nodes;
myalgia;
rash on the chest, back and stomach.

As a rule, such manifestations of infection persist for several days.

Severe WN fever is extremely rare - out of about 150 infected people, only one person suffers a severe illness. Such infected people exhibit the following symptoms:

high fever;
stupor;
headaches;
shiver;
stiffness of the neck muscles;
muscle weakness;
convulsions;
numbness;
paralysis;
loss of vision.

These signs of infection may last for several weeks. After this the patient long time manifestations of neurological consequences persist.

Possible complications

Consequences of MN fever occur in most cases only during the neuroinfectious course of the disease. With the development of meningoencephalitis, the following may develop:

paralysis;
paresis.

In rare cases, the infection leads to the death of the patient.

More often, the neuroinfectious course of this disease causes:

swelling of brain tissue;
cerebrovascular accidents.

Diagnostics

PCR helps detect in blood or other biological environments patient fragments genetic material(DNA) of the causative virus.

When making a diagnosis, the doctor takes into account clinical, epidemiological and laboratory data. The following signs may indicate infection:

acute onset;
relatively short duration of fever;
systemic damage to mucous tissues, organs and lymph nodes;
serous meningitis;
stay in endemic dangerous regions and the fact of being bitten by a mosquito or tick.

To assess the patient's condition, the following studies are performed:

– leukopenia;
virological analysis to detect WN fever virus (on culture media or on laboratory mice);
enzyme-linked immunosorbent assay (ELISA);
lumbar puncture followed by collection of cerebrospinal fluid for analysis (it will reveal a slight increase in protein levels, pleocytosis).

To exclude erroneous diagnosis, it is carried out differential diagnosis with the following diseases:

and other acute respiratory infections;
acute lymphocytic choriomeningitis;
listerellosis;
tuberculosis;
rickettsiosis.

Treatment

So far, scientists have not been able to develop drugs for etiotropic treatment ZN fever. The patient is advised to remain in bed and take symptomatic medications.

West Nile fever (West Nile encephalitis) is an acute viral zoonotic natural focal disease with a transmission mechanism for transmitting the pathogen. It is characterized by an acute onset, pronounced feverish-intoxication syndrome and damage to the central nervous system.

ICD-10 code

A92.3. West Nile fever

Epidemiology of West Nile fever

The reservoir of West Nile fever virus in nature is birds of the aquatic complex, the carrier is mosquitoes, primarily ornithophilous mosquitoes of the genus Cilex. Between them, the virus circulates in nature; they determine the possible distribution area of West Nile fever - from the equatorial zone to regions with a temperate climate. Currently, West Nile fever virus has been isolated from more than 40 species of mosquitoes, included not only in the genus Clekh, but also in the genera Aedes, Anopheles, etc. The importance of specific mosquito species in epidemic process, occurring in a certain territory, has not been clarified. The work of Russian scientists has established the infestation of Argasid and Ixodid ticks in natural foci West Nile fever.

Synanthropic birds may play an additional role in the persistence and spread of the virus. The 1999 West Nile fever outbreak in New York was accompanied by mass mortality of crows and the death of exotic birds at the zoo; in 2000-2005 The epizootic spread throughout the United States. The epidemic in Israel in 2000 was preceded by an epizootic in 1998-2000. among the geese on the farms. About 40% of poultry in the Bucharest area had antibodies to West Nile virus in the fall of 1996. Together with “urban” ornithophilic and anthropophilic mosquitoes, domestic and urban birds can form the so-called urban or anthropogic focus of West Nile fever.

What causes West Nile fever?

West Nile fever is caused by the West Nile virus, which belongs to the genus Flavivirus families Flaviviridae. The genome is represented by single-stranded RNA.

Virus replication occurs in the cytoplasm of affected cells. West Nile fever virus has a significant ability to vary, which is due to the imperfection of the mechanism for copying genetic information. The greatest variability is characteristic of genes encoding envelope proteins responsible for the antigenic properties of the virus and its interaction with tissue cell membranes. Strains of West Nile fever virus isolated in different countries and in different years are not genetically similar and have different virulence. The group of “old” strains of West Nile fever, isolated mainly before 1990, is not associated with severe damage to the central nervous system. A group of “new” strains (Israel-1998/New York-1999, Senegal-1993/Romania-1996/Kenya-1998/Volgograd-1999, Israel-2000) strains are associated with massive and serious illnesses person.

What is the pathogenesis of West Nile fever?

West Nile fever has been little studied. It is assumed that the virus spreads hematogenously, causing damage to the vascular endothelium and microcirculatory disorders, in some cases the development of thrombohemorrhagic syndrome. It was established that viremia is short-term and not intense. The leading factor in the pathogenesis of West Nile fever is damage to the membranes and substance of the brain, leading to the development of meningeal and cerebral syndromes and focal symptoms. Death occurs, as a rule, on the 7-28th day of illness due to a violation of vital important functions due to edema-swelling of the brain substance with dislocation of stem structures, necrosis of neurocytes, hemorrhages in the brain stem.

What are the symptoms of West Nile fever?

The incubation period of West Nile fever lasts from 2 days to 3 weeks, most often 3-8 days. West Nile fever begins acutely with an increase in body temperature to 38-40 ° C, and sometimes higher within several hours. An increase in temperature is accompanied by severe chills, intense headache, pain in the eyeballs, sometimes vomiting, pain in the muscles, lower back, joints, and severe general weakness. Intoxication syndrome is expressed even in cases that occur with short-term fever, and after normalization of temperature, asthenia persists for a long time. The most characteristic symptoms of West Nile fever caused by “old” strains of the virus, in addition to those listed, are scleritis, conjunctivitis, pharyngitis, polyadenopathy, rash, hepatolienal syndrome. Dyspeptic disorders are common (enteritis without pain syndrome). Damage to the central nervous system in the form of meningitis and encephalitis is rare. In general, West Nile fever is benign.

Every spring, when the weather warms up, mosquitoes emerge from hibernation and/or hatch from their eggs. As soon as the temperature environment at night it begins to stay at +10 ° C, bloodsuckers begin to become more active. This means that if you are often outside at this time, these pests will already be looking for victims.

Mosquitoes are more than just a nuisance, they carry diseases! West Nile fever is usually spread by mosquitoes. Not only people, but also pets are susceptible to this disease. Not everyone who is bitten develops this disease, but it can be fatal (mortality rate: 5.5% to 7.5% of those infected), and the most dangerous thing about it is that there is no specific cure for West Nile fever.

What is West Nile virus?

West Nile virus was first discovered in 1937 in Uganda, in the USA in 1999, and in Russia at about the same time. Natural foci of this virus are in southern countries the former USSR, as well as in the south of Russia, although imported cases do occur. This virus is transmitted to humans by mosquitoes, but it is usually spread over long distances by birds. The latter become infected precisely from mosquitoes or from eating infected birds (if the birds are predatory).

Most birds live after infection, but some, such as crows and jays, often die. There is no evidence that humans can catch the virus from birds, but to avoid it, it is best not to touch dead birds with your bare hands.

Mosquitoes transmit the virus to humans through a bite. Only females do this; they need blood to produce eggs. Oral apparatus in females it is specially adapted for this; they pierce the skin with their proboscis and first inject a little of their saliva. Thanks to this, the blood does not immediately clot and the mosquito can easily drink blood. It is this mixture of saliva and blood that transmits the West Nile virus to humans.

Incubation period for West Nile fever

A person may develop symptoms within a couple of days after being bitten by an infected mosquito, but it can take up to 2 weeks, according to the Centers for Disease Control and Prevention. Only one in five people bitten by a mosquito infected with West Nile virus develop symptoms at all. A fever is common, but it is important to know what symptoms to watch for. Only one percent of people bitten develop the severe reaction that results in West Nile fever, and it has long-lasting symptoms:

Weakness
Depression
Tremor
Fatigue quickly
And other signs of brain damage

Common symptoms of West Nile fever

Symptoms vary from person to person, depending on the individual's response to the virus. West Nile virus is not contagious, but can be transmitted from person to person in some rare ways:

Blood transfusion
From mother to child during pregnancy and breastfeeding
Organ transplantation

Once you are bitten by an infected mosquito, whether you develop symptoms or not, you are immune to the virus and will not get it again.

Most people infected do not develop symptoms, but a small percentage of people may develop mild symptoms, such as:

Fatigue quickly
Headache
Body pain
Back pain
Vomit
Diarrhea

Sometimes other symptoms may develop:

Pain in the eyes
Swollen lymph nodes

There is no specific treatment for mild cases of the disease.

Who is at higher risk of getting infected?

Age, current state health and other factors may play a role in an individual's response to the virus. Children and older people are most susceptible to this disease, so it is important to know what symptoms to pay special attention to.

The symptoms of West Nile fever in children are no different from those in adults and carry the same risks as in adults. Children are more likely to develop a mild fever, rash, and mild cold-like symptoms.

In older people or people with weak immunity The risk of developing West Nile encephalitis is significantly higher, and it can cause permanent brain damage.

If you are in a region where West Nile virus infection is possible, or are planning to travel there, you need to pay special attention to the following symptoms (especially for older people; remember, there is no vaccine for this fever in humans yet):

Severe headache
Rigidity occipital muscles
High fever
Brain fog
Tremor
Convulsions
Sudden muscle weakness
Paralysis

Anyone experiencing these symptoms should seek immediate medical attention. These are symptoms of West Nile encephalitis. West Nile fever is not usually fatal, but some people develop serious neurological conditions which can lead to death.

Diagnosis and treatment of West Nile fever

A doctor can diagnose West Nile fever in three ways:

Test your blood for antibodies to the virus
Check brain activity using EEG and MRI
Take a cerebrospinal fluid test to check if the white count has increased blood cells in it

West Nile fever is treated depending on the severity of the condition. Most people recover at home simply by taking painkillers, sufficient quantity fluids and rest.

In cases of complications, such as encephalitis and meningitis, there is no treatment as such, but without hospitalization these conditions can be fatal. The hospital provides maintenance therapy, prevents other infections, intravenous infusions, and connects the device artificial ventilation lungs and sometimes use immunoglobulin.

Researchers are working to create a vaccine and develop other treatments, but to date there is no specific therapy or vaccine for West Nile fever.

West Nile virus in animals

Mosquitoes can transmit West Nile virus to dogs, cats, horses and other pets. Knowing the symptoms of West Nile fever in animals can help protect them. Fever manifests itself differently in different animals, but just like in people, older animals and those with weakened immune systems are more susceptible to infection and complications.

Dogs

West Nile symptoms in dogs are often confused with a cold or respiratory disease. Symptoms include:

Fever for several days
Muscle weakness and pain
Swollen lymph nodes

Symptoms may appear as early as a day after the bite and may become more or less severe, depending on the condition. immune system your dog and how his body will react to the virus. Dogs, like people, are also at risk of developing encephalitis, which can lead to death if left untreated.

If you are in an area where there are outbreaks of West Nile virus, your veterinarian may perform a blood test to diagnose West Nile virus if your dog shows signs of encephalitis. Dogs usually recover within a few days, but if this does not happen, the dog will need veterinary care, including intravenous infusions.

Cats

Cats can become infected with West Nile virus from mosquito bites and from eating infected birds. They usually develop only mild symptoms, such as lethargy and fever, but more serious symptoms can occur. But you are unlikely to understand that the cat was infected with the West Nile virus, since they do not have any specific manifestations.

Horses

In horses, symptoms appear 5 to 15 days after being bitten by an infected mosquito. As in humans and dogs, symptoms vary from individual to individual and depend on the reaction to the virus.

The most common symptoms of West Nile fever in horses include the following:

Weakness in the limbs
Muscle twitching
Deterioration of coordination
Frequent stumbling
Partial paralysis
Fever (sometimes)

Most horses can make a full recovery at home with the support of a veterinarian. In severe cases, horses require hospitalization. While in the hospital, the horse may need IV fluids and medications to control its fever. Treatment may also include:

Turning over to avoid bedsores
Head and foot protection
Infusion therapy
Intravenous nutrition

A West Nile virus vaccine for horses exists, but it must be used before infection. If you are in an area where there are outbreaks of West Nile virus, vaccination should be discussed with your veterinarian before mosquito season begins. Sometimes vaccination is not so necessary, because only 17% of infected horses develop relapses and other complications after recovery.

Where does West Nile virus occur?

Most often, infection occurs from June to September. In America, disease outbreaks occur in almost every state except Hawaii and Alaska. In Russia, the first cases were registered in 1999 in the Volgograd and Astrakhan regions. Since then, in addition to imported cases, infections in Russia are not uncommon, and this number has increased over the years. In 2008, a reference center for monitoring the causative agent of West Nile fever was created in Volgograd. In 2016, 135 cases of infection were recorded throughout Russia, and in 2017 there were only 12. There are factors that influence the number of cases of infection:

Number of birds in the area where the virus lives
Weather conditions(ambient temperature and humidity suitable for mosquitoes)
People's behavior
Mosquito population size

Not all mosquitoes carry West Nile virus. There are hundreds of species of mosquitoes in the world, but only a small percentage are known vectors, such as:

Asian tiger mosquito (not long ago this mosquito appeared in Russia in the Altai region, but so far they are not dangerous)
The common mosquito lives in almost all regions of Russia, but only a few of them in the southern regions of the country can be carriers of West Nile

No matter what type of mosquito lives in your yard, the best way to prevent West Nile fever is to prevent them from biting you. This means you need an effective, long-term way to reduce the mosquito population in your yard.

What is needed for prevention? Avoid being bitten by infected mosquitoes! The same goes for your family and pets. With this a huge amount When considering mosquito repellent methods, you need to decide which one will be most effective for your family.

You can buy repellents, use citronella candles, and even make your home mosquito-proof. Repellents containing DEET can be effective against mosquitoes, but they must be constantly updated to keep working.

You can (and this is even necessary) try to protect your home from mosquitoes so that they do not fly to you and do not bite you at night. To do this you need:

Install or repair mosquito nets on windows and doors.
Remove all standing water around your home (birdbaths, old tires, pet bowls, ponds, etc.)
Report dead birds found to your health department or environmental authority. Don't touch them!
Use laurelicides to kill mosquito larvae in ponds and fountains around your home.

These methods will help you reduce your risk of being bitten by an infected mosquito, but they are not very long-term solutions, and no one wants to sit at home all the time. To fully enjoy outdoor activities and reduce the likelihood of contracting West Nile fever, best protection is a long-term solution with proven effectiveness and safety, such as traps from Mosquito Magnet.

Traps convert propane into carbon dioxide, then they heat it up, moisten it (to make it look like human breath) and add an additional attractant (simulating the smell of human skin). This combination attracts mosquitoes, they fly closer to the trap and are then sucked inside, where they dry out and die within 24 hours.

Maintaining the trap is very simple; you just need to perform a few steps every 21 days:

Refilling a propane tank
Change the attractant

It is also important to ensure that the insect net is clean and intact, even if the number of mosquitoes being caught is not very large. Dirty and damaged meshes reduce the effectiveness of Mosquito Magnet traps.

Works immediately, but may take about 4 weeks to break the mosquito breeding cycle around your home. These traps attract mosquitoes from an area of up to 40 acres, but effectively protect (destroy up to 90% of the population) from 6-14 acres, depending on the model:

The trap operates from a 15-meter power cord and protects an area of up to 6 acres*
The model is wireless, battery powered and protects an area of up to 14 acres*
The trap is also wireless and battery powered and protects an area of up to 10 acres*

*provided that the site is surrounded by a sufficiently high impenetrable fence

Mosquito Magnet traps have 18 years of research and more than 15 patents behind them, making these destroyers technologically revolutionary.

Mosquito Magnet mosquito killers are quite expensive, but you will be able to use their protection for many years and will help you reduce the mosquito population in your yard. In our store, Mosquito Magnet traps come with a two-year warranty. They are in a great way control the population of infected mosquitoes. They cover enough area to protect your family and pets from mosquito bites that can lead to West Nile fever.

Mosquito Magnet traps are EPA registered and scientifically proven to be effective. If you want to reduce your chances of contracting West Nile Virus, you should choose the best mosquito trap for you. To effectively control the mosquito population, such exterminators should be placed as soon as the air temperature at night begins to remain at +10 ° C, then the very first awakened or born mosquitoes will be destroyed.

West Nile fever (WNF) is a zoonotic, naturally occurring, vector-borne infection caused by arboviruses of the Flaviviridae family, characterized by an acute intoxication syndrome affecting the central nervous system.

Vector-borne infections are a group of diseases whose pathogens are transmitted by blood-sucking arthropods. IN in this case The role of virus carriers is played by mosquitoes of the genus Culex, less commonly by Aedes and Anopheles; the participation of ixodid and argasid ticks in the transmission of the virus cannot be ruled out. Natural reservoir for West Nile virus - wild birds.

The virus is quite resistant to external environment: dies at temperatures above 55 ºС with exposure for at least half an hour, remains viable for a long time in dried or frozen form.

Initially, West Nile fever was most widespread in Africa. South America, Asia. Since the end of the last century, the nosoarea of the disease has expanded significantly: cases of infection are being detected in countries not only with hot, but also with temperate climates (in Europe, Russia), which is due to the seasonal migration of infected birds.

Temperate regions experience a characteristic seasonality; the peak incidence (more than 90% of all detected cases) occurs from July to October, which correlates with the maximum number of blood-sucking insects in these months.

Risk groups for infection with the West Nile virus include people working or relaxing on their plots, as well as hunters, fishermen - people who spend a lot of time in the favorite places of arthropods (in ponds, shady areas with massive vegetation, in swampy or wooded areas).

Causes and risk factors

The cause of the disease in the vast majority of cases is the bite of an infected mosquito or tick.

The virus enters the blood-sucking body through the blood (where it circulates for several days) after the bite of an infected bird. Subsequently, the causative agent of West Nile fever is concentrated in salivary glands insect or tick, from where, when bitten by a person or animal, it moves into his bloodstream, causing a chain of pathological changes.

In addition to insect bites, the virus can be transmitted vertically (from mother to child), as well as through transfusion infected blood or transplantation of infected organs, but this happens extremely rarely.

Forms of the disease

West Nile fever can occur in 2 forms:

manifest – typical develops clinical picture with violent symptoms;
asymptomatic – in this case, there are no manifestations of the disease (according to the World Health Organization, the frequency of this form is close to 80% of the total incidence).

The natural reservoir for West Nile virus is wild birds.

The manifest form of the disease is represented by two clinical variants:

WNV without damage to the central nervous system (occurs in a flu-like form or in a flu-like form with neurotoxicosis);
WN with damage to the central nervous system (meningeal and meningoencephalitic forms).

Symptoms

The incubation period of the disease lasts up to 3 weeks, more often – 5-6 days. Subsequently, if a manifest form of the disease occurs, a characteristic specific option infection symptoms.

Manifestations of West Nile fever that is not accompanied by damage to the central nervous system:

acute onset of the disease;
rise in body temperature to 39-40 ºС, in exceptional cases– above 40 ºС (the duration of the febrile period can reach 12 days, although on average it is limited to 2-3 days);
tremendous chills;
drenching sweat;
polymorphic maculopapular rash (noted quite often);
headache;
pain when moving the eyeballs;
increased sensitivity to light, photophobia;
muscle and joint pain;
enlargement and tenderness of the lymph nodes of the head and neck upon palpation;
hyperemia of the mucous membranes of the pharynx;
a long period of asthenia after relief of intoxication symptoms (general weakness, drowsiness, decreased performance, feeling of weakness).

In the case of an infection with symptoms of neurotoxicosis, the headache becomes intense, episodes of dizziness are possible, nausea, vomiting at the height of fever, unsteadiness of gait, and stiff neck are typical. Any changes during analysis cerebrospinal fluid in this case it is not registered.

When involved in infectious process central nervous system (with meningeal form) symptoms are as follows:

acute onset with a rapid increase in body temperature to critical levels, chills, sweating;
intense headache, becoming painful on the 3rd-4th day;
stiff neck;
photophobia;
nausea, vomiting with meningeal symptoms.

Based on the results of a lumbar puncture, changes in the cerebrospinal fluid characteristic of serous viral meningitis are determined.

In the meningoencephalitic form of the disease, the patient's condition is severe or extremely severe, severe general cerebral symptoms are noted against the background of the phenomena of meningoencephalitis (impaired consciousness, headache, dizziness, vomiting, generalized convulsive attacks), which further develops cerebral coma. The mortality rate for this form of the disease is 5–10%, in extremely severe cases – up to 40%.

Diagnostics

Diagnosis of West Nile fever is difficult due to a large number asymptomatic cases of the disease, the absence of specific manifestations in influenza-like forms.

Basic diagnostic measures:

collection of epidemiological history (connection with previous stay in high-risk areas, bites of blood-sucking insects, seasonality of the disease);
carrying out solid phase enzyme immunoassay(ELISA) to detect specific IgM, IgG (titer confirming diagnosis - 1:800 or more);
carrying out polymerase chain reaction(PCR) to detect West Nile virus RNA;
virological study to identify the pathogen;
in the presence of meningeal symptoms - lumbar puncture followed by examination of the cerebrospinal fluid.

Risk groups for infection with the West Nile virus include people working or relaxing on their plots, as well as hunters and fishermen.

Treatment

Treatment of WNV is medicinal. Appointed:

interferon inducers;
diuretics;
glucocorticosteroid hormones;
inhalation of humidified oxygen.

Detoxification therapy and correction are carried out electrolyte disturbances and blood osmolarity. If necessary, anticonvulsants are used, sedatives, antioxidants, agents that improve cerebral blood flow, antibiotics wide range actions.

Possible complications and consequences

Complications of West Nile fever are very serious:

acute cerebrovascular accident;
cerebral edema;
coma, death.

Forecast

At timely diagnosis And complex treatment the prognosis is favorable. Probability good outcome the disease decreases with infection of the meningoencephalitic form of severe or extremely severe course.

Mortality in the meningoencephalitic form of the disease is 5–10%, in extremely severe cases – up to 40%.

Prevention

Preventive measures are as follows:

Carrying out activities aimed at reducing the population of blood-sucking insects.
Decrease in the population of wild birds, whose lifestyle is associated with direct living near humans.
The use of repellents during prolonged stays in natural areas with high risk arthropod bites.

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