Runny nose

How does rabies manifest itself in cows? Mad cow disease: real or imaginary threat? What is the disease

Any farmer should monitor the health of his animals, because the issue is not only about maintaining economic indicators and business profitability, but also about basic safety. There are a number of diseases that are equally dangerous for both animals and people; moreover, a person can become infected with them by eating infected meat. One such disease that poses a deadly threat to both cattle and humans is spongiform encephalopathy, sometimes also called mad cow disease or mad cow disease.

What kind of disease is this

Humanity became acquainted with this problem quite recently. In the mid-80s of the last century, several thousand English cows were simultaneously affected by an unknown disease. Almost simultaneously, similar symptoms were detected in cattle in Ireland, and then in some other countries of Western Europe.

But England continued to suffer most from the strange epidemic: in 1992, tens of thousands of little cows had already died here.
The signs of the disease were very reminiscent of rabies: there was anxiety, fear of closed spaces, aggression, fear of light and sound, a nervous reaction to touch, a desire for solitude, and grinding of teeth. For this reason, the disease received its common name, which often misleads farmers about its nature.

Important! Spongiform encephalopathy has nothing to do with rabies. These diseases have a completely different nature, pathogen, mechanism of infection and course. The only thing they have in common is some symptoms, this is explained by the fact that in both cases the central nervous system and brain are affected.

Rabies is viral in nature, while the causative agent of spongiform encephalopathy is not a virus, not a bacterium, or even a fungus. It turns out that the disease is caused by an ordinary protein molecule, which is present on the surface of nerve cells, in the brain and bone marrow of animals and people, but at a certain moment, for some reason, takes on a configuration that is not typical for it.
Such a sensational discovery was made in 1982 by the English biochemist Stanley Prusiner. He called the “twisted” protein molecule that causes fatal brain damage a “prion.”

The development of the disease occurs as follows. “Incorrect” prions are attracted to each other, creating a clot or plaque on the nerve cell. As a result, the nerve cell dies, and in its place a cavity filled with cell sap appears, the so-called vacuole. As the disease progresses, such vacuoles fill the entire brain, turning it into a kind of sponge (hence spongiform encephalopathy).

Of course, the functions of the brain are irreversibly impaired, and the organism affected by the disease dies.

How does infection occur?

For a long time, scientists could not figure out why exactly the “twisting” of protein molecules in nerve cells occurs. In the end, an assumption was made, which has not been refuted to this day, that it was enough for one “wrong” prion to enter the body for neighboring molecules to begin to rearrange themselves in its image and likeness.
The mechanism of this phenomenon remains not fully understood, but the fact that one “black sheep” somehow infects “the whole herd” is almost beyond doubt.

Upon deeper study of the mechanism of infection, it was found that the source of the disease (that very wrong molecule) most likely entered the body of the unfortunate cows with meat and bone meal added to their food by English farmers. This flour is made from sheep carcasses, and sheep also suffer from prion diseases.

Thus, the meat and bones of sick sheep turn into poison, slowly killing other, larger animals.

Answering the question why meat and bone meal, which has long been added to the diet of cows, began to kill cows only in a certain period of time, scientists found that the outbreak of the epidemic coincided with the introduction of significant changes in the technological process of making flour, or, more precisely, its simplification by abandoning some stages that additionally disinfect the raw materials.
And indeed, as soon as meat and bone meal was excluded from the feed, the cows began to get sick less, and the epidemic subsided. But at the same time, another problem arose - people began to get sick with spongiform encephalopathy.

Important! Mad cow disease is transmitted to humans through the meat of a sick cow, which he eats. Infection does not occur from direct contact with an animal.

This feature of disease transmission means that spongiform encephalopathy takes on the nature of an epidemic not because animals infect each other, but because they receive the same food.

If a cow infected with “imaginary rabies” gets into the herd, it will not infect its companions, but the disease can be transmitted intrauterinely, that is, calves born by such a cow will most likely also be sick.

Forms and signs of rabies in cattle

One of the main problems associated with the diagnosis and, accordingly, with the very possibility of treating spongiform encephalitis is that this disease has a very long incubation period. In cows it can last from 2.5 to 8 years, and in people the disease has a latent form even longer, sometimes up to 30 years.

But when the disease makes itself felt, it progresses quickly and is not accompanied by temporary improvements in the condition.

Did you know? The discovery of a new deadly cow disease has caused real panic. English farmers were forced to slaughter more than 3.5 million cows, and, most likely, the vast majority of them were completely healthy. Many countries (including Russia) have banned the import of meat from Great Britain into their territory, which has caused losses in the Albion's agriculture running into billions of pounds.

It is customary to distinguish 2 forms of the disease:

acquired(sometimes it is also called variant or sporadic, since it occurs in individual individuals and is not epidemic in nature);
hereditary(an animal becomes infected in the womb of a sick mother and is born with the disease).

As for the symptoms of the disease, they can be divided into “violent” ones, associated with changes in the behavior of the sick cow, and those that characterize the general condition of the animal.

Violent

An animal suffering from spongiform encephalopathy develops unreasonable fear, however, if ordinary viral rabies is characterized by severe fear of hydrophobia, then prion infection manifests itself as an acute negative reaction to any irritants - light, noise, bodily contact.

A cow may kick its owner for no apparent reason, lose its leading position in the herd, begin to tremble all over, and bump into obstacles. In general, this block of symptoms is very similar to the clinical picture of rabies.

Calm

In addition to obvious changes in behavior, spongiform encephalopathy can be recognized by some other, “calm” symptoms, which include:

impaired motor skills and coordination of movements (ataxia): this symptom sometimes lasts several weeks, and in other cases lasts for months;
limping gait;
frequent movement of the ears;
nose licking;
scratching the head (for this purpose, the animal may rub against various objects or even try to reach the head with its foot);
blurred vision;
twitching and involuntary contraction of muscles, accompanied by severe pain;
weight loss (with continued appetite);
reduction in milk yield;
in the final stages - failure of the hind limbs, coma and death.

In humans, characteristic signs of spongiform encephalopathy are memory loss, dementia and other disorders of brain activity, depression and insomnia, tingling in the limbs, but in a cow these symptoms (of course, also occur) are quite difficult to recognize.

Important! Unlike true rabies, with spongiform encephalopathy there is never an increase in body temperature. This symptom can distinguish 2 diseases that are similar in clinical picture.

Diagnostics

Clinical and epidemiological information does not allow us to accurately diagnose spongiform encephalopathy, since its symptoms are similar to many other diseases of cattle, and these include not only rabies.

Today, there are 2 main ways to diagnose spongiform encephalopathy:

biochemical (histological);
immunological.

Biochemical diagnostic method The first method involves studying a section of the brain under an electron microscope in order to identify voids (vacuoles) and prion plaques that form threads on it.

Immunological diagnostics involves the use of special antibodies that interact with deformed prions, entering into a reaction with them that can be detected. There is a reaction - the analysis is positive, there is no reaction - there is no disease. This method is definitely more reliable and informative than a visual examination.

The only “small” problem is that it can only be done on killed animals. In other words, the immunological diagnostic method is good when it is necessary to check whether beef, for example, brought from countries that are at risk for mad cow disease, can be eaten.
Immunological diagnostic method

It is this method that is used today in Western Europe, where the meat processing plant, at the stage of preparing cow carcasses for processing, conducts a preliminary analysis of them for spongiform encephalopathy; this takes about 10 hours.

However, experiments to diagnose people for the presence of latent forms of the disease are already underway - cerebrospinal fluid or a piece of tissue taken from the throat is taken for analysis.

Is it possible to cure

Unfortunately, timely and correct diagnosis is not needed for treatment, but only for maintenance therapy (in humans) and making a decision about the possibility of eating meat (in relation to cows).

Important! Spongiform encephalopathy is incurable and is fatal in 100% of cases. Moreover, unlike viral rabies, there is no vaccination against this disease (given the specific nature of the pathogen, it is most likely impossible in principle).

In humans, death from “mad cow disease” occurs within a period of six months to a year from the moment the first symptoms of the disease are detected. However, given the very long incubation period, if the problem is detected in time, its development can be slightly delayed.

One hundred percent mortality and the impossibility of vaccination make spongiform encephalopathy extremely dangerous, even though the likelihood of a person getting such an exotic disease cannot be called high.

Yes, today About 80 (according to other sources - 200) people died from mad cow disease in the world, and these figures are comparable to the statistics of deaths from “real” rabies, which, although it is fatal, is only possible if timely measures are not taken to introduce a vaccine.
However, it must be understood that the number of deaths from spongiform encephalopathy may increase significantly in the future due to those who ate meat from infected cows before the dangerous disease was recognized (if the alarm was first sounded in 1985, and the development of the disease in humans can last 30 years, it is likely that the worst consequences of the infection have not yet manifested themselves).

It is important to know that eating the meat of a diseased animal, including wild animals such as deer or elk, is indeed the most likely way of infecting a person with mad cow disease (unlike the true rabies virus, the “causative agent” of spongiform encephalopathy is not contained in the saliva of animals). However, more exotic ways of introducing infection are also possible.

Did you know? Some tribes of New Guinea, who still use cannibalism in ritual ceremonies, became infected with “mad cow disease” after eating human meat. There are also cases of infection of people who have undergone transplantation or blood transfusion, that is, from sick donors. For this reason, by the way, in the UK today donor blood is not accepted from people living in regions mentioned as hotbeds of the spread of “mad cow disease”.

In addition to meat, milk and dairy products can also be sources of contamination, and we are talking not only about cow’s milk, but also about sheep’s and goat’s milk.

Prevention of mad cow disease

In the absence of a vaccine, the only possible way to prevent the inevitable death from mad cow disease is prevention. And precautions should apply not only to farms that keep cows and other disease-prone livestock, but also to enterprises that process and sell their meat and milk, and to the end consumers of these products.

For countries where the situation with mad cow disease looks good (those, fortunately, include Russia, Ukraine and Belarus; however, as skeptics say, the problem has passed us by rather because domestic livestock farmers simply cannot afford to buy meat -bone meal produced in England, and feed their cows with local hay and mixed feed), preventive measures come down to following a few simple rules:

Limiting the import of meat products from states or territories where even isolated cases of spongiform encephalopathy have been reported. This should apply not only to meat and offal, but also to semi-finished products, embryos, sperm, biological tissues, meat and bone meal and other feed and feed additives of animal origin, technical fat, so-called intestinal raw materials, cheeses and other dairy products.
The most careful inspection of all breeding animals imported into the country, especially from England and other European countries.
Non-use of meat and bone meal made from sheep and cattle carcasses as feed additives.
Purchase of feed and feed additives only if you have an appropriate certificate confirming that the product has passed testing for spongiform encephalopathy.
Mandatory laboratory examination of the brains of sheep and cattle that died of unknown causes, as well as slaughtered carcasses intended for sale.

Laboratory research of animal brains as a measure to prevent mad cow disease

In Great Britain, Ireland, Germany and other countries unfavorable from the point of view of mad cow disease, prevention has been taken to a more serious level. The most radical measure, which, however, many residents of these countries have long resorted to, is a complete refusal to eat beef, lamb, goat and lamb.

As for government measures to combat the deadly disease, the British, for example, have developed a special system for identifying cases of mad cow disease. The country periodically conducts random inspections of meat products intended for sale.

Did you know? Ordinary protein molecules begin to fold, turning into a gel, at a temperature of 65–70 °C, but the causative agent of mad cow disease (a pathogenic prion that has already changed its natural configuration) is destroyed at temperatures above 1000 °C! Thus, ordinary, even very thorough, heat treatment of meat infected with mad cow disease does not make it suitable for consumption. It is interesting to note that the common rabies virus dies instantly when heated to 100 °C, and within 2 minutes at 80 °C.

But in the United States of America, back in 1997, the Food and Drug Administration (FDA) banned the inclusion of animal proteins in feed for cattle and small livestock.

Thus, unfortunately, little depends on us. If the meat of an animal infected with mad cow disease somehow ends up on our table, infection and subsequent death (in the distant future, but without options) will inevitably await us. As long as we remain in our homeland, there is no particular cause for concern, except perhaps meat and dairy products should be purchased only from trusted manufacturers.

On the other hand, although spongiform encephalopathy is an English disease that has been transmitted to some Western European countries, the situation there has already been brought under strict government control.

In New Guinea, people ate the brains of the dead as part of a funeral ritual. This led to a disease called kuru, a central nervous system disorder that caused mad cow disease in cows.

Known medically as bovine spongiform encephalopathy, mad cow disease affects the central nervous system of livestock. This disease belongs to the group of transmissible spongiform encephalopathies (TSEs), neurodegenerative diseases that affect animals and humans.

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In animals, other related diseases include scrapie (in sheep) and feline spongiform encephalopathy (in cats). A person develops diseases such as Gerstmann-Straussler-Scheinker syndrome and sporadic fatal insomnia. Mad cow disease syndrome is believed to result from the presence and exposure to prions, which are infectious agents that contain an abnormal form of protein.

Transmission of these infectious agents occurs through protein misfolding. They are mainly present in the brain, spinal cord, small intestine and blood of livestock. They can also be found in the lymph nodes, spleen and bone marrow of the affected organism. In addition, some scientists are of the opinion that proteins present in the body are converted into prions due to the presence of a certain type of virus. However, this theory has not yet been confirmed by research. Prions damage the central nervous system by forming spongy holes. This leads to degeneration of nerve cells, which ultimately leads to the death of the body.

Research and laboratory data suggest a strong association between mad cow disease syndrome and variant Creutzfeldt-Jakob disease in humans. It is a neurodegenerative human disease that is usually fatal. It is associated with the consumption of contaminated meat or meat products.

The earliest symptoms include depression, insomnia and anxiety.
The person may appear withdrawn and in a state of confusion.
There are significant changes in a person's personality and behavior.
A person may also experience muscle spasms, i.e. involuntary muscle contractions that cause severe pain.
As the person's condition worsens, they lose muscle control and coordination, and may experience problems with vision (blurred vision) and memory.
Temporary memory loss is another symptom that makes it difficult for the patient to recognize people. This symptom also makes it difficult to perform everyday tasks.
The patient may experience a tingling sensation in the feet, palms, face and legs.
He may develop dementia, which makes him weak mentally and physically.
At the last stage of the disease, the patient may fall into a coma, which ultimately leads to death. The onset of the last stage occurs within a period of 6 months to one year after the onset of symptoms.

Mad cow disease invariably develops in cattle.

Decreased ability to stand and walk.
Problems with muscle coordination.
Slight change in behavior.
Sudden weight loss.
Significant reduction in milk production.

How is mad cow disease spread?

As already mentioned, the causative agent of this disease is prions. They cannot be transmitted from one organism to another through physical contact, but can enter the body of humans and animals in the following ways:

At slaughterhouses, animal remains are disposed of without any testing. The waste/by-products are fed to livestock as a cheap source of protein. If animal remains contaminated (with prions) get into the feed, the prions are transmitted to the livestock.
When a person begins to consume meat contaminated with the causative agent of mad cow disease syndrome, this also exposes him to the risk of infection.
Variant Creutzfeldt-Jakob disease has been reported to develop in people, including vegetarians, without any known cause. It is believed that the development of this disease in humans may be a consequence of a genetic mutation that is inherited.
In addition, transfusion of contaminated blood, transplantation of tissue containing prions, and the use of contaminated surgical instruments can lead to the development of this disease in humans.

Diagnosis and treatment

There is no special technology or physical test to diagnose this disease. However, your doctor may recommend a complete blood count along with an MRI and PET scan, and may also order a brain biopsy to check for changes in the brain.

Unfortunately, there is no effective treatment or cure for this disease. Researchers continue to search for a drug that could help cure this disease in both humans and animals. However, the patient may be prescribed certain medications to control symptoms. Love, care and moral support can help cope with the disease.

To avoid the development of this disease, it is recommended to take certain preventive measures. You should limit your consumption of red meat. Heating, cooking, and exposure to radiation or chemicals do not destroy prions. Therefore, cooking contaminated meat does not guarantee its safety for consumption. Another good way to prevent the development of this disease is to switch to a vegetarian diet. If any of the above symptoms appear, you should consult your doctor as soon as possible.

Description

Cattle rabies (Bovine Rabies) is a viral infection of the central nervous system: in sick individuals, inflammatory and necrotic processes in the central nervous system and specific encephalitis are observed. As a result, the cow dies from asphyxia or cardiac arrest. Rabies is divided into 2 types based on the source of infection. The natural type is observed in wild animals such as wolves, foxes, and bats. Carriers of urban rabies are dogs, cats, and cattle.

Etiology pathogenesis

Pathogen Cattle rabies is a special virus, Neuroryctes rabid, which belongs to the family Rhabdoviridae and has a bullet shape. Strains of Neuroryctes rabid are dangerous for all warm-blooded animals. This virus is widespread on all continents, with the exception of Antarctica and a number of island countries.
Biology of the pathogen:
After entering the body, the rabies pathogen penetrates the spleen and from there spreads along the nerve pathways. The virus is relatively stable in the external environment: at low temperatures it remains viable for many months, and when the remains of dead livestock decompose it remains dangerous for another 2-3 weeks. Inactivation of the virus requires heat treatment (more than 10 minutes at temperatures above 60°C or short-term at 100°C) or disinfection using solutions of chloramine, formalin or alkali.
Epizootological data:
Warm-blooded animals of all species are susceptible to the rabies virus. Foxes, jackals, and wolves are most susceptible to it. Cats and cattle are recognized to be highly sensitive. The source of the infectious agent is sick animals and virus carriers, which release the virus into the external environment mainly with saliva 3-8 days before the appearance of clinical signs of the disease. Infection occurs mainly through a bite, less often through salivation, through nutritional and aerogenic routes.
Rabies is characterized by natural focality and periodicity, which are associated, respectively, with the presence in nature of a reservoir of the rabies virus - wild carnivores, especially foxes, and with a three-year periodicity of decline in the population of these animals. The disease occurs in sporadic cases, the mortality rate is 100%.
Pathogenesis and pathological data:
Infection occurs when the virus enters damaged skin or mucous membranes due to bites or salivation. The bite is found in approximately 91% of animals killed by rabies. From the site of primary localization, the virus penetrates the central nervous system and causes the development of non-purulent encephalitis. From the brain, the virus travels through the centrifugal nerves to the salivary glands, where it reproduces and is excreted in saliva. Pathological changes in the central nervous system lead to the development of a nervous syndrome, and subsequently to paralysis of the respiratory or cardiac organs and death of the animal.
When autopsying corpses, no characteristic changes are found. Dogs are found to have: a lack of food in the stomach, sometimes foreign objects in it: cyanosis of the mucous membranes; acute venous hyperemia of the brain, liver, lungs and spleen; blood thickening, dry serous tissue, subcutaneous tissue and skin. During histological examination, Babes-Negri bodies were found in the nerve cells of ammon's horns.

Symptoms and clinical signs

Consultation with a veterinarian

Rabies in a cow or bull occurs in violent or calm form. The violent stage is characterized by the following symptoms: increased irritability, which manifests itself in sudden movements and aggressive behavior directed at other cows and small domestic animals; excessive sweating; salivation; frequent urination.
The calm form is manifested by atypical lethargy of livestock, lack of appetite, and depression. Cows stop producing milk, the ruminant reflex disappears, and difficulties with swallowing appear.
The symptoms of violent and quiet rabies described above are characteristic of the initial stage of the disease, which occurs after the incubation period (from 14 days to 3 months, sometimes up to a year). A few days after the first symptoms appear, cows develop paralysis of the lower jaw, after which both pairs of limbs fail and the animal dies.
The main typical symptoms of bovine rabies also include an increased reaction to noise and light, including convulsions, body tremors, and a sharp decrease in weight. Some cows lose vision as the disease develops.

Diagnostics

Consultation with a veterinarian

Clinical observation is used to diagnose cattle rabies. Livestock that have had suspicious contacts with possible carriers of the infection are isolated in a separate room and undergo regular veterinary examination. High titers of the rabies virus are found in studies of the cerebral cortex and ammon's horns, and in analyzes of the medulla oblongata. Lower concentrations of the virus are detected in the lacrimal and salivary glands.

Treatment and prevention

Consultation with a veterinarian

There is no treatment for rabies. When sick animals are identified, they are urgently isolated and destroyed in accordance with the requirements of sanitary standards.
The only effective preventative measure is the rabies vaccine. It allows you to launch the mechanism for producing antibodies that quickly neutralize the virus when it enters the body. As a result of the administration of the drug, biochemical processes are observed in the cow’s body that reduce the susceptibility of body cells to the pathogen. Modern vaccines are made based on the Paster/RIV virus strain, which has an activity of more than 2 IU. The dosage of the vaccine is 1 ml. Administration of the drug is intramuscular. Before vaccination, it is necessary to conduct an examination by a veterinarian to assess the general condition of the animal: only healthy cows are vaccinated at the age of 6 months and every 2 years thereafter. The need for regular prevention of rabies in cattle allows not only to avoid livestock deaths, but also to protect people who come into contact with animals and consume dairy and meat products. Once infected cows are identified, they cannot be transported outside the farm, and the dairy products obtained from the herd are destroyed.

Rabies is an acute infectious disease that occurs with severe damage to the nervous system, usually with a fatal outcome. Humans and all mammals are susceptible.

Rabies is widespread. The causative agent of infection is transmitted by dogs, cats, wild rodents and predators, as well as blood-sucking vampire bats.

The duration of the incubation period depends on the location and strength of the bite, the amount and virulence of the virus that has entered the wound, and the resistance of the bitten animal. The incubation period lasts from 1-3 weeks to a year or even more.

The disease is acute. Its clinical signs are basically the same in all animals, but they are most typical in dogs, in which both violent and silent (paralytic) course of the disease can be observed. In cattle, rabies can have an atypical course (loss of appetite, rumen atony, pharyngeal paralysis, drooling). There may not be an arousal stage. Pathological changes are not specific. In meat-eaters (mainly dogs), foreign objects can be found in the stomach.

The rabies virus has pronounced neuroprobasia. Penetrating from the periphery (site of the bite) along the nerve trunks into the central (nervous system) centripetally, it spreads in the body centrifugally along the peripheral nerves and enters various organs, including the salivary glands.

The virus belongs to the family Rhabdoviridae, genus Lyssavirus. Virions have the shape of a rod with a chopped end. The virus virion is RNA-containing with a helical type of symmetry and has a lipoprotein envelope. Low temperatures preserve the virus. A temperature of 60°C kills it in 5-10 minutes, sunlight – in 5-7 days. Solutions of formalin, phenol, hydrochloric acid (5%) inactivate the virus in 5-10 minutes.

The rabies virus virion contains glycoprotein (external) and nucleocapsid (internal) antigens. The glycoprotein antigen induces the formation of virus-neutralizing antibodies, and the nucleocapsid antigen induces complement-fixing and precipitating antibodies.

Epizootic strains of the rabies virus are immunobiologically related, but differ in virulence.

In the body, the virus is localized mainly in the central nervous system, as well as in the salivary glands and saliva. Cultivated on mice, rabbits, guinea pigs and other animals, as well as in primary cell cultures (Syrian hamster kidneys, sheep embryos, calves, etc.) and continuous cells (VNK-21, KEM-1, etc.). Reproduction of the virus in cell cultures does not always manifest itself as CPE. After preliminary adaptation, chicken embryos are also susceptible to the rabies virus. The virus induces the formation of cytoplasmic inclusion bodies, which are most often found in the cells of the ammon's horn, cerebellum, and cerebral cortex.

The source of infection is sick animals. They transmit the virus through a bite. Carnivores can become infected by eating the brains and spinal cords of animals that have died from rabies. The possibility of rabies infection through aerogenous transmission (in places where there are bats) has been proven. Until the 1960s, the main source of rabies was dogs and cats, later foxes, wolves, corsacs and other wild animals.

The diagnosis of rabies is made on the basis of epidemiological, clinical data and laboratory test results, which are of critical importance.

When working with sick animals and infectious material, it is necessary to strictly observe personal safety measures: wear rubber gloves, gowns with sleeves, a rubber or polyethylene apron, rubber boots, safety glasses, and a protective face mask.

It is prohibited to open animals suspected of having rabies in the field.

Laboratory diagnostics. It includes: detection of viral antigen in RIF and RDP, Babes-Negri bodies and a bioassay on white mice.

Methodology for setting up RIF.

Thin impressions or smears are prepared on fat-free glass slides from various parts of the brain on the left and right side (ammon's horn, cerebral cortex, cerebellum and medulla oblongata). At least two preparations of each part of the brain are prepared. You can also examine the spinal cord and submandibular salivary glands. For control, preparations are made from the brain of a healthy animal (usually a white mouse).

The preparations are dried in air, fixed in chilled acetone (minus 15-20 ° C) for 4 to 12 hours, dried in air, fluorescent gamma globulin is applied, placed in a humid chamber at 37 ° C for 25-30 minutes, then washed thoroughly saline or phosphate buffer with a pH of 7.4, rinsed with distilled water, dried in air, applied non-fluorescent immersion oil and viewed under a fluorescent microscope. In preparations containing the rabies virus antigen, yellow-green fluorescent granules of different sizes and shapes are observed in neurons, but more often outside cells. In control, there should be no such glow; nervous tissue usually glows with a dull grayish or greenish color. The intensity of the glow is assessed in crosses. The result is considered negative if there is no specific fluorescence.

Material from animals vaccinated against rabies cannot be examined in the RIF for 3 months. after vaccination, as there may be fluorescence of the vaccine virus antigen.

Tissues preserved with glycerin, formaldehyde, alcohol, etc., as well as material that shows signs of even slight decay, are not subject to examination in the RIF.

RDP in agar gel. The method is based on the property of antibodies and antigens to diffuse in an agar gel and, upon meeting, form visually visible precipitation lines (antigen + antibody complex). Used to detect antigen in the brain of animals that have died from street rabies virus, or during experimental infection (bioassay).

The reaction is carried out on glass slides, onto which 2.5-3 ml of a molten 1.5% agar solution is poured. After hardening in agar, wells are made using a stencil with a diameter of 4-5 mm, placed under a glass slide with agar. Agar columns are removed with a student's pen. The wells in the agar are filled with components according to the diagram.

All parts of the brain (left and right sides) are examined from large animals; from medium animals (rats, hamsters, etc.) - any three parts of the brain; in mice - the entire brain. Using tweezers, a paste-like mass is prepared from the brain, which is placed in the appropriate wells.

Controls with positive and negative antigens are placed on separate glass using the same stencil.

After filling the wells with the components, the preparations are placed in a humid chamber and placed in a thermostat at 37 °C for 6 hours, then at room temperature for 18 hours. The results are recorded within 48 hours.

The reaction is considered positive when one or 2-3 lines of precipitation of any intensity appear between the wells containing the brain suspension and rabies gamma globulin.

Bacterial nonsterility and brain decay do not prevent its use for RDP. Material preserved with glycerin, formalin and other means is not suitable for RDP.

Identification of Babes-Negri bodies. Thin smears or prints are made on glass slides from all parts of the brain (as for RIF), at least two preparations from each part of the brain, stained using one of the methods (according to Sellers, Muromtsev, Mann, Lenz, etc.).

An example of Sellers staining: a dye is applied to a fresh, undried preparation, covering the entire preparation, left for 10-30 s and washed off with phosphate buffer (pH 7.0-7.5), dried in a vertical position at room temperature (in a dark place) and viewed under an oil immersion microscope.

A positive result is considered to be the presence of Babes-Negri bodies - clearly defined oval or oblong granular formations of pink-red color, located in the cytoplasm of cells or outside them.

This method has diagnostic value only when typical specific inclusions are detected.