Tularemia. Tularemia. The causative agent of the disease, epizootic data, the course of the disease in farm animals, the course and symptoms of the disease, pathoanatomical changes, diagnosis, prevention and control measures, prevention of commercial pests

Tularemia- zoonotic infection with natural foci. It is characterized by intoxication, fever, damage to the lymph nodes.

Pathogen

The causative agent of the disease is a small bacterium Francisella tularensis, belongs to the family francisellaceae, kind Francisella. This is a small gram-negative polymorphic (mainly coccoid) bacillus, immobile, does not form spores. Some strains have a thin capsule. The causative agent of tularemia is characterized by high resistance in the environment, especially at low temperatures and high humidity (survives at −30 °C, remains in ice for up to 10 months, in frozen meat up to 3 months), less resistant to drying (in the skins of rodents that have died from tularemia). lasts up to 1.5 months at room temperature and up to 1 week at 30 °C). Remains viable in river water at a temperature of 10 °C up to 9 months, in soil up to 2.5-4 months, on grain, straw at a temperature of −5 °C up to 190 days, at 8 °C up to 2 months, at 20-30 °C up to 3 weeks. It is stored for a long time in milk, cream at low temperatures. It is not resistant to high temperatures (at 60 ° C it dies in 5-10 minutes, at 100 ° C - within 1-2 minutes), sunlight, UV rays, disinfectants (solutions of Lysol, chloramine, bleach kill it in 3 -5 minutes). In vitro tularemia bacteria are sensitive to streptomycin and other aminoglycosides, levomycetin, tetracycline, rifampicin, resistant to penicillin and its analogues.

epidemiological data

Animals of different species are susceptible. The causative agent is isolated from the body of fish, amphibians, reptiles, insects, carnivores, pinnipeds, rodents, equids, artiodactyls, insects, crustaceans. Under natural conditions, hares, wild rabbits, mice, water rats, muskrats, beavers, hamsters suffer from tularemia; cats and dogs are less sensitive to the pathogen; very sensitive person.
The source of the causative agent of infection is rodents, as well as sick farm animals. Infection occurs by alimentary and aerogenic routes, as well as by the bites of blood-sucking arthropods (ixodid and gamasid ticks, fleas, mosquitoes, horseflies, etc.). Possible intrauterine infection. In farm animals, the disease is often asymptomatic, but sporadic outbreaks can occur in sheep, cattle, horses, pigs, reindeer, camels, rabbits, poultry, and cats. The young are more susceptible. Outbreaks of tularemia often appear in the spring-summer-autumn periods of the year, which is associated with a more intensive migration of rodents and the activity of blood-sucking insects. The environment of pigs and sheep, especially young animals 2-6 months of age, the disease is recorded in November-January, that is, during the period of migration of mice to livestock buildings. Some researchers believe that outbreaks of tularemia in sheep are preceded by epizootics of this disease in hares. Natural foci of tularemia are confined to the habitats of rodents. These foci remain active for a long time (50 years or more).

Pathogenesis

The pathogen enters the body. From the place of primary localization, it enters the bloodstream, enters the lymph nodes, spleen, lungs and other organs, which leads to the development of sepsis and the death of the animal.

Course and symptoms

The incubation period for tularemia lasts from 4 to 12 days, and depending on the type of animal, the disease can be acute or mild.

Sheep , especially lambs, in the acute course of the disease, there is an increase in temperature to 40.5-41 ° C, lethargy, rapid breathing, a shaky gait. After 2-3 days, the body temperature drops to the stern, followed by a secondary rise. Patients develop signs of conjunctivitis and rhinitis; submandibular and prescapular lymph nodes are enlarged, dense, painful. Due to a sharp decrease in hemoglobin content (by 2 times or more), anemia develops, and later - paralysis of the hind limbs. Death occurs in 8-15 days. The incidence of lambs reaches 10-50%, and up to 30% of the diseased die. With an erased course of the disease, which occurs in adult sheep, there is a slight depression and an increase in body temperature by 0.5 ° C. After 2-3 days these signs disappear and the animals recover.
piglets tularemia is manifested by an increase in body temperature up to 42 ° C, oppression, coughing and profuse sweating, as a result of which the skin becomes dirty and covered with crusts. High body temperature is maintained for 7-10 days, and if there are no complications from the respiratory organs, a slow recovery occurs. Most of the patients die.
Cattle, buffaloes, horses and camels sick latently, with erased signs. Abortions are possible in pregnant animals.
Chickens, pheasants, pigeons are more often asymptomatic.

In rabbits and fur animals note rhinitis, abscesses of subcutaneous lymph nodes, emaciation. Most of the patients die.

In dogs clinical symptoms are usually rare or mild.

In cats clinical symptoms are as follows: depression; anorexia and fever; lymphadenopathy, splenomegaly, hepatomegaly; ulceration of the tongue and oral cavity; abscesses; jaundice. Transmission of infection from cats to humans has been noted. Clinical symptoms in humans and cats are similar.

Pathological changes

In dead animals, they find hemorrhages and foci of necrosis in the subcutaneous tissue, hyperemia, swelling of the mucous membrane of the nasopharynx, purulent plugs in the tonsils, a focus of hyperemia in the submandibular, pharyngeal and prescapular lymph nodes; in sheep and piglets, in addition, serous-fibrinous pleuropneumonia. With a prolonged course, abscesses of the lymph nodes and in the internal organs. Lesions in rodents are similar to the pathological changes observed in pseudotuberculosis.

Diagnosis

They put it on the basis of an analysis of epizootological, clinical, pathoanatomical data, taking into account the results of bacteriological, serological and allergic studies. Suspicion of tularemia in agricultural and domestic animals occurs when this disease is present in rodents. For research, the corpses of rodents, the corpses of small animals are sent to the veterinary laboratory, and from the corpses of large animals, the heart, the affected lymph nodes.

Prevention and control measures

Human tularemia

Epidemiology and pathogenesis

Tularemia is characterized by a variety of gates of infection. The following routes of infection are distinguished: through the skin (contact with infected rodents, transmissible transmission by blood-sucking insects), through the mucous membranes of the digestive organs (consumption of contaminated water and food) and the respiratory tract (inhalation of infected dust). Clinical forms of the disease are closely related to the gates of infection. With contact and transmissible infection, bubonic and skin-bubonic forms of the disease develop, with aspiration - pneumonic, with alimentary - intestinal and anginal-bubonic forms of tularemia. When infected with tularemia through the conjunctiva, an oculo-bubonic form occurs. After a disease, immunity develops.

Clinical picture

The incubation period is from several hours to 3-7 days. There are bubonic, pulmonary, abdominal and generalized (spread throughout the body) forms. The disease begins acutely with a sudden rise in temperature to 38.5-40°C. There is a sharp headache, dizziness, pain in the muscles of the legs, back and lumbar region, loss of appetite. In severe cases, there may be vomiting, nosebleeds. Severe sweating, sleep disturbance in the form of insomnia or vice versa drowsiness are characteristic. Often there is euphoria and increased activity against the background of high temperature. There is redness and swelling of the face and conjunctiva already in the first days of the disease. Later, petechial hemorrhages appear on the oral mucosa. The tongue is covered with a grayish coating. A characteristic feature is an increase in various lymph nodes, the size of which can be from a pea to a walnut. From the side of the cardiovascular system, bradycardia and hypotension are noted. In the blood, leukocytosis with a moderate neutrophilic shift. The liver and spleen are not enlarged in all cases. Pain in the abdomen is possible with a significant increase in mesenteric lymph nodes. The fever lasts from 6 to 30 days. At bubonic form In tularemia, the pathogen penetrates the skin without leaving a trace; after 2-3 days of illness, regional lymphadenitis develops. The buboes are slightly painful and have clear contours up to 5 cm in size. Later, either the softening of the bubo occurs (1-4 months), or its spontaneous opening with the release of thick creamy pus and the formation of a tularemia fistula. The axillary, inguinal, and femoral lymph nodes are most commonly affected. The ulcerative-bubonic form is characterized by the presence of a primary lesion at the site of the entrance gate of infection. The oculo-bubonic form develops when the pathogen enters the mucous membranes of the eyes. The appearance of yellow follicular growths up to millet grain size on the conjunctiva is typical. Bubo develops in the parotid or submandibular areas, the course of the disease is long. The anginal-bubonic form occurs with a primary lesion of the mucous membrane of the tonsils, usually one. Occurs during the food route of infection. There are forms of tularemia with a predominant lesion of internal organs. Pulmonary form - more often recorded in the autumn-winter period. characterized by prolonged fever of the wrong type with repeated chills and profuse sweat. Patients complain of chest pain, cough, initially dry, then with mucopurulent, and sometimes with bloody sputum. X-ray reveals focal or lobar infiltration of the lung tissue. Pneumonia is characterized by a sluggish protracted course (up to 2 months or more), recurrence. Abdominal Ithe form develops due to damage to the lymphatic vessels of the mesentery. It is manifested by severe pain in the abdomen, nausea, vomiting, and sometimes diarrhea. Generalized form resembles severe sepsis. Symptoms of intoxication are expressed: severe fever, weakness, chills, headache. Confusion, delusions, hallucinations may occur. Perhaps the appearance of a persistent rash all over the body, buboes of various localizations, pneumonia. This form can be complicated by infectious-toxic shock. Complications can be specific (secondary tularemia pneumonia, peritonitis, pericarditis, meningoencephalitis), as well as abscesses, gangrene caused by secondary bacterial flora. Diagnosis is based on a skin-allergic test and serological reactions.

Prevention

Provides control over natural foci of tularemia, timely detection of epizootics among wild animals, carrying out deratization and pest control measures. In the case of human illness, the sources of the infectious agent and the circumstances of infection are established. Further actions depend on the specific situation. In particular, in case of a water outbreak, it is necessary to prohibit the use of unboiled water; in case of transmissible infection, visits to places where it could occur are temporarily limited, etc. Specific prophylaxis (vaccination) is carried out with a live tularemia vaccine.

Tularemia (tularemia) is a transmissible, natural focal infectious disease characterized by septicemia, fever, lymphadenitis, lesions of the mucous membranes of the upper respiratory tract and intestines, as well as the nervous system. A person is highly sensitive to the disease.

The disease is common in many countries of the world, including in the Republic of Belarus.
Economic damage consists of the incidence of farm animals (lambs) up to 50% and mortality up to 30%. The death of rabbits, fur-bearing animals, chickens can reach 90%.

Etiology . The causative agent of tularemia - Francisella tularensis of the genus Francisella Dorogeev - is a small polymorphic cocci-like bacillus (0.2-0.7 microns), immobile, does not form spores, has a capsule, gram-negative. Aerobe, cultivated on special media. The causative agent is divided into 3 varieties according to virulence and antigenic structure: American, European-Asian and Central Asian. Bacteria are capable of long-term existence outside the body: in water at 13-15 ° C they persist for 3 months, in frozen meat - up to 93 days, in milk - up to 104 days, in the body of pasture mites - up to 240 days, direct sunlight kills pathogen in 30 minutes, heating at 60 ° C - in 5-10 minutes. solutions of conventional disinfectants (formaldehyde, phenol, lysol, etc.) reliably neutralize environmental objects from the pathogen (group 2).

epidemiological data . Mainly hares, mice, water rats, muskrats, beavers, hamsters are susceptible. Sporadic cases of tularemia have been reported in sheep, cattle, horses, pigs, rabbits, poultry, and cats. Cats and dogs are less sensitive, human susceptibility is considered high.

The source of the infectious agent is mainly rodents, as well as large farm animals. Infection occurs by alimentary and aerogenic routes, as well as by the bites of blood-sucking arthropods (ticks, fleas, mosquitoes, etc.). The disease is characterized by spring-summer-autumn seasonality and stationarity. Tularemia is a natural focal disease associated with rodent habitats. It occurs in farm animals in the form of sporadic cases, in wild animals - in the form of epizootics. Morbidity up to 50%, mortality up to 90%.

Pathogenesis . The pathogen enters the body with food, aerogenically or through the bite of blood-sucking arthropods. From the place of primary localization, it enters the bloodstream, enters the lymph nodes, spleen, lungs and other organs, which leads to the development of sepsis and the death of the animal.

The course and symptoms of the disease. The incubation period for tularemia is 4-12 days, depending on the type of animal, the disease is acute or mild. The acute course of the disease occurs in sheep, especially in lambs, and is characterized by an increase in body temperature up to 41 ° C, lethargy, unsteady gait, conjunctivitis, rhinitis, anemia, paralysis of the hind limbs and mortality within 8-15 days.

In piglets, tularemia is manifested by an increase in body temperature, coughing and profuse sweating. With complications from the respiratory system, most piglets die.

In rabbits and fur animals, rhinitis, abscesses of subcutaneous lymph nodes, emaciation and death of most animals are noted.

The rest of the animals are asymptomatic. Abortions are possible in pregnant animals.

pathological changes. At autopsy, hemorrhages and foci of necrosis in the subcutaneous tissue, hyperemia, swelling of the mucous membrane of the nasopharynx, purulent plugs in the tonsils are found; in sheep and piglets, in addition - serous-fibrinous pleuropneumonia, abscesses in the lymph nodes and in the internal organs.

Diagnostics is based on taking into account the epizootological features of the disease, clinical signs, the nature of pathological changes and the results of bacteriological, serological (RA) and allergic (tularin) studies.

Differential diagnosis. Tularemia should be differentiated from anaplasmosis, tuberculosis, paratuberculosis, brucellosis, eimeriosis.

Treatment. Antibacterial drugs (antibiotics, sulfonamides, etc.) are used to treat sick animals. There are no specific treatments.

Immunity. There are no specific means of preventing tularemia in animals.

Tularemia- an infectious disease of rodents, farm animals and poultry. Man also suffers from tularemia!

Tularemia bacterium Francisella tularensis

Spread of disease and economic damage . Tularemia has been observed in humans and animals in many parts of the world.

The disease brings great losses to sheep breeding. The disease is accompanied by a large death of lambs and a decrease in the productivity of adult animals. Tularemia is a serious danger to humans. The source of infection are rodents and industrial animals.

Tularemia is the source of infection

The causative agent of the disease. Francisella tularensis - polymorphic immobile bacterium in size from 0.2 to 0.7 microns, does not form spores, gram positive.

External factors through which a person can become infected: rodents, blood-sucking insects

Epizootology of the disease. The most susceptible to tularemia are water rats, field and house mice, muskrats, beavers, hares, rabbits and cats; from farm animals - sheep, cattle, horses and pigs. Artificially it is possible to infect buffaloes, camels, goats and dogs. Sporadic cases have been described in chickens and wild birds.

Rodents are a source of infection for pets. , which pollute pastures, fodder, and water with their secretions and corpses. The causative agent of the disease can be carried by stinging insects and ticks.

Source of animal infection: rodents and ticks

The pathogenesis of tularemia is not well understood.. The infection develops as a bacteremia with damage to the vascular and lymphatic systems and the formation of necrosis in the liver, lungs and spleen. Microbes can be released into the external environment with urine and faeces.

Tularemia - signs of the disease

Clinical signs and course of the disease. In cattle, the course of the disease is mostly latent, but there may be an increase in lymph nodes, the appearance of mastitis and paralysis of the limbs. In weaned piglets, the disease is characterized by fever, depression, loss of appetite, rapid breathing, and cough. In horses, along with the latent course of infection, abortions are also observed.

Heavier tularemia passes into the lambs. The disease begins with a 2-3 day fever. Sick animals lag behind the herd, stand with their heads down, pulse and breathing are accelerated, feces are liquid. The mucous membranes are anemic. The pharyngeal, cervical and lobed lymph nodes are enlarged. Catarrhal, rhinitis, paresis and paralysis of the hind limbs are sometimes observed. The disease is fatal in most cases.

Micropreparation of a lung affected by tularemia

pathological changes. The corpses of animals that died from tularemia are depleted. Lymph nodes (pharyngeal, cervical, lobed) are enlarged, sometimes with the formation of abscesses. The liver is enlarged with the presence of small foci of necrosis, which are also found in the lungs. The spleen is edematous, its pulp is dark red. For all dead animals, the phenomena of septicemia (blood poisoning) are characteristic.

Human finger affected by tularemia

Diagnosis. When making a diagnosis of tularemia, epizootic data are taken into account, and bacteriological studies are also carried out.

For allergic diagnosis in sheep, tularin is used.

differential diagnosis. Tularemia must be distinguished from diseases such as,,, anaplasmosis and, using clinical and epizootological data, pathological changes detected during autopsy, the results of bacteriological examination of pathological material.

Tularemia - treatment, immunity, disease prevention

Treatment. Treatment methods for tularemia have not been developed.

Immunity and immunization. Animals that have recovered from tularemia develop strong immunity.

A rodent that carries the bacterium tularemia

The corpses of dead animals are burned, disinfected, manure is disinfected by the biothermal method.

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Tularemia (lat. - Tularemia) is a natural focal, transmissible infectious disease of mammals of many species, birds and humans, manifested by septicemia, fever, lesions of the mucous membranes of the upper respiratory tract and intestines, enlargement and cheesy degeneration of regional lymph nodes (lymphadenitis), the appearance inflammatory-necrotic foci in the liver, spleen and lungs, emaciation, mastitis, abortion, damage to the nervous system and paralysis.

The disease was first discovered in 1908 in Tulare County (California, USA) in rodents. McCaw and Chapin (1911) were the first to isolate the culture of the pathogen. Then, in the same US state, the disease was found in people and sheep (1921). E. Francis suggested calling it tularemia. Tularemia is registered in North America, Japan, Europe, Asia and Africa. The disease is distributed mainly in landscapes of the temperate climate zone of the Northern Hemisphere. In our country, it was first registered in 1921. The economic damage caused by tularemia to animal husbandry is generally insignificant, since a clinically pronounced disease is rare in farm animals. However, anti-tularemia measures require high costs.

Currently, the genus Francisella includes two species - Francisella tularensis and Francisella philomiragia, and the species F. tularensis is represented by four subspecies - F. tularensis subsp tularensis (type A), F. tularensis subsp holarctica (type B), F. tularensis subsp mediaasiatica and F. tularensis subsp novicida.

Type A causes more severe disease in humans and is pathogenic in rabbits. Found only in North America. Considered as a probable bacteriological weapon. To solve the problem of national biological safety, Decree of the President of the Russian Federation No. 2194 of December 4, 2003 was issued. The pathogen is included in the "List of pathogens (pathogens) of humans, animals and plants, genetically modified microorganisms, toxins subject to export control in order to protect national interests and ensure fulfillment of the international obligations of the Russian Federation arising from the Convention on the Prohibition of the Development, Production and Stockpiling of Bacterial (Biological) and Toxin Weapons and on Their Destruction" (Decree of the President of the Russian Federation No. 1004 of August 8, 2001)

Type B is found in North America, Europe and Asia. It causes milder human diseases, does not ferment glycerol and citrulline, and is not pathogenic for rabbits (when infected with a type A pathogen, rabbits die when even 1 microbial cell is injected, type B - 1 billion cells). The causative agent is stable in the external environment. It remains in water up to 3 months, in grain, straw - up to 6 months, in the organs of dead animals - 2-3 months, in skins - up to 40 days. Pathogens are sensitive to streptomycin, chloramphenicol, tetracycline. In relation to erythromycin, two variants circulate in our country - resistant and sensitive.

Virulent varieties contain O-, H-, V-antigens, and avirulent varieties contain only O-antigen.

The causative agent of tularemia exhibits considerable stability in the external environment, especially at low temperatures, but at the same time it is very sensitive to various physical (solar, ultraviolet rays, ionizing radiation, high temperature) and chemical influences.

The causative agent - Francisella tularensis - is a small coccus-like rods (0.3-0.5 microns), immobile, gram-negative. The microbe does not form spores, has a small capsule. In cultures, the formation of mucus by bacteria is characteristic, which is easily detected when making smears on glass. Tularemia bacteria stain with all dyes commonly used in laboratory practice, but are noticeably paler than many bacteria. Strict aerobes. In serological reactions, they react well with Brucella. They do not grow well on nutrient media (special enriched media are required).

Microbes are cultured on yolk media with the addition of cystine and other nutrients, especially blood. The temperature optimum is 36-37°C. Isolated colonies are conveniently obtained by inoculation on plates with Emelyanova's medium (hydrolyzate of fish meal, gelatin, yeast, sodium chloride, glucose, cystine, agar) or Francis's medium - (meat-peptone agar with 1% peptone, 0.5% - sodium chloride, cystine, glucose). After sterilization, these media are added to 5-10 ml of defibrinated rabbit blood. Colonies on these media are whitish with a bluish tinge, round, with a smooth edge, convex, smooth, shiny; with sparse inoculation, they reach (after a few days) 1-2 mm or more in diameter.

125 species of vertebrates and 101 species of invertebrates are susceptible to tularemia. Under natural conditions, hares, wild rabbits, mice, water rats, muskrats, beavers, hamsters and chipmunks are ill with tularemia. Natural foci can be active for 50 years or more. Of the farm animals, lambs and piglets under the age of 2.4 months, cattle, horses and donkeys are the most sensitive to the causative agent of tularemia and can become ill with clinically pronounced signs of the disease. Of poultry, chickens (especially chickens) are the most susceptible. Turkeys, ducks and geese show high resistance to infection. Dogs and cats are less susceptible to the pathogen. Of the laboratory animals, guinea pigs and white mice are the most susceptible.

Infection of agricultural and wild animals occurs mainly by alimentary, aerogenic and transmissible routes.

The causative agent of tularemia penetrates through microtraumas of the skin and through the mucous membranes. In these cases, skin-bubonic or ocular-bubonic forms of tularemia occur (the latter form can develop when infected water enters the conjunctiva).

At the use of water or products contaminated with rodents, intestinal or anginal-bubonic forms of tularemia occur.

Infection can occur by aerogenic means (inhalation of infected dust), which often leads to the development of the pulmonary form of tularemia.

Outbreaks of tularemia are observed both in the spring-summer (pasture) and autumn-winter (stall) period, which is associated, respectively, with increased activity of blood-sucking insects and more intensive migration of rodents to livestock buildings, food storage areas in certain seasons of the year.

Suspicion of wild animal tularemia is usually caused by the increased cases of death of rats and mice. Sick hares, wild rabbits and squirrels lose their natural fear of humans, do not flee and allow themselves to be easily caught.

The incubation period for tularemia in farm animals (sheep, goat, pig, horse) lasts from 4 to 12 days. Depending on the species, breed and age of animals, the disease can proceed acutely, subacutely or chronically, manifest itself in a typical or atypical (erased, latent, asymptomatic, innaparant) form.

In sick lambs, relaxation and paresis of the hind limbs, diarrhea and pallor of the mucous membranes (anemia due to a decrease in hemoglobin concentration to 40.30 g / l at a rate of 70.80 g / l), catarrhal conjunctivitis and rhinitis, accompanied by serous-mucous discharge from the nose, are noted. The mandibular and prescapular lymph nodes are enlarged, dense, painful. With the progression of the disease, in addition to these symptoms, there is a sharp anxiety and extreme agitation. During this period, paralysis appears in some animals, then a coma sets in and the sick die within the next few hours. The disease lasts 8.15 days. The incidence of lambs is 10.50%, and the lethality is 30%.

In adult pigs, it often proceeds hidden. In piglets of 2.6 months of age, after an incubation period of 1.7 days, the disease manifests itself with an increase in body temperature up to 42°C, refusal to feed, depression, rapid abdominal breathing and coughing. There is profuse sweating, as a result of which the skin becomes dirty and covered with crusts. Lymph nodes are enlarged. High body temperature is maintained for 7-10 days, and if there are no complications from the respiratory organs, a slow recovery begins. Otherwise, in sick animals, progressive emaciation is noted. Most of them die.

In cattle, the disease in most cases proceeds without visible clinical signs (asymptomatically) and is detected only by serological research methods. In some cases, sick cows have short-term fever, swollen lymph nodes and mastitis. In pregnant animals, abortions are possible (50 days after infection). The general condition and appetite remain unchanged. Cases of the manifestation of the disease in the form of paralysis of the limbs with a fatal outcome are described.

With tularemia infection in horses, mild and asymptomatic forms of the disease are observed, detected by allergic and serological studies. Under conditions of natural infection, tularemia in mares is usually manifested by mass abortions at the 4.5th month of pregnancy without any subsequent complications. Body temperature remains normal. In donkeys, body temperature rises by 1.2°C and remains at this level for 2 weeks. Anorexia and exhaustion are observed.

For the development of the disease when introduced into the skin or by aspiration, 10-50 viable microorganisms are sufficient, and with alimentary infection, more than 108 microbial cells are needed.

An inflammatory process develops at the injection site, massive multiplication of microbes occurs, then they penetrate into the regional lymph nodes, causing inflammation. Microbes multiply, partially die, releasing endotoxin, which enters the bloodstream and causes general intoxication. When microbes enter the blood, hematogenous dissemination occurs in various organs and tissues. There is a multiple increase in lymph nodes, granulomas can develop in different organs (liver, spleen, lungs). The granulomatous process is especially pronounced in the regional lymph nodes, where areas of necrosis are formed. A large number of granulomas are found in the spleen, liver. In terms of cellular composition, tularemia granulomas resemble those of tuberculosis. The transferred disease leaves behind stable immunity.

For the first time, the phenomenon of the transition of the causative agent of tularemia into an uncultivated state under the influence of environmental conditions was described. It was shown that revertants of uncultivated forms of the tularemia microbe restore their basic properties, including virulence. The existence of such dormant forms is directly related to the reservation of the pathogen and its adaptation to adverse environmental conditions. It has been determined that the causative agent of tularemia is endowed with adaptive plasticity important for persistence, which manifests itself in its adequate response to environmental stress factors. A complex of molecular biological techniques for the detection and identification of the causative agent of tularemia has been proposed. A DNA probe for identification has been designed and tested, and specific primers have been designed to indicate the causative agent of tularemia. Universal (random) primers were selected for studying the genome (PCR typing, genomotyping, genotyping) of the tularemia microbe in a single primer PCR system. For the first time, the place of PCR in the practice of epizootological and epidemiological surveillance of tularemia in natural foci was determined. The PCR method, subject to low-temperature storage of field material samples, increases the efficiency of epizootological monitoring of territories, as it provides the possibility of accelerated preliminary selection of positive samples for subsequent targeted bacteriological analysis, and also makes it possible to detect tularemia microbes that are in an uncultivated state in which they persist in the environment during the inter-epizootic period.

The corpses of dead animals are depleted. The skin in the axillary region is ulcerated and necrotic. Under the skin and in the subcutaneous tissue of various parts of the body, compacted areas with hemorrhages and foci of necrosis are found. The mandibular, pharyngeal, prescapular and axillary (and with a protracted course, internal) lymph nodes are enlarged and purulently inflamed. The mucous membrane of the nose is edematous and hyperemic. The pharynx is hyperemic; at the root of the tongue and in the tonsils caseous-purulent plugs. In lambs and piglets, in addition, fibrinous pleurisy and focal serous-fibrinous pneumonia, congestive hyperemia and necrotic foci in the liver are found. The spleen is swollen, its pulp on the cut has a dark red color and serous-yellow nodules. Pinpoint hemorrhages on the epicardium and adrenal glands. In general, a general picture of sepsis is created.

Pathological anatomical signs in rodents are similar to those observed in pseudotuberculosis.

Suspicion of tularemia arises in the presence of this disease in rodents (mass mortality), diseases of agricultural and domestic animals, as well as humans.

An express diagnostic based on agglutination is used, only for analysis it is not the serum that is taken, but a drop of the patient's whole blood and is also mixed with the tularemia diagnosticum. With a positive reaction, the red blood cells stick together (this happens if the content of antibodies in the patient's blood is high enough). For more accurate diagnosis, RPHA (direct hemagglutination reaction) and ELISA (enzymatic immunoassay) are used.

Serological methods - agglutination reaction, RPHA (direct hemagglutination reaction), ELISA (enzymatic immunoassay). Diagnostic is the increase in the number of antibodies in the course of the disease, the agglutination reaction becomes positive from 10-12 days of illness. Serum is taken at the beginning of the disease and at the 2-3rd week. Diagnostic is the increase in the number of antibodies against the tularemia bacillus by 4 times or more. To set up the reaction, a tularemia diagnosticum is used, containing 10 billion tularemia bacteria killed by formalin in 1 ml of solution. If there are corresponding antibodies in the patient's serum, the formation of flakes can be seen when the serum and diagnosticum are mixed. This is a positive reaction based on the fundamental interaction of antigens and antibodies. The method is quite fast, but tentative.

Allergic method (allergic skin test). This method is based on the peculiarity of a patient or a person who has recovered from tularemia to respond with a local allergic reaction to the introduction of tularin (a suspension of heat-killed tularemia sticks). This analysis makes it possible to diagnose "tularemia" at the earliest possible time, since the intradermal allergic test becomes positive already from the 3rd-5th day of illness. Tularin is administered intradermally at a dose of 0.1 ml, taken into account after 24 and 48 hours. A positive reaction is manifested by the appearance of hyperemia and infiltration of the skin with a diameter of 0.5 cm or more.

For bacteriological examination, the whole corpses of rodents and small animals are sent to the veterinary laboratory, and from the corpses of large animals - the liver, kidneys, spleen, heart, affected lymph nodes. In the veterinary laboratory, bacterioscopy is carried out, seedings are made from the pathological material, followed by identification of the isolated cultures by cultural, morphological, biochemical and antigenic properties.

With a bioassay, an isolated culture, a suspension of pieces of organs and lymph nodes infect guinea pigs or white mice and, if necessary, examine the material in a precipitation reaction. In guinea pigs experimentally infected with a bioassay (the death of which is noted after 2.3 days), inflammation and ulceration at the site of injection of the biomaterial (or pathogen culture), suppuration of regional lymph nodes, enlargement of the spleen and liver, nodular and focal lesions in the lungs are considered pathognomonic changes. White mice die on the 3.4th day after infection. Diagnostic signs in them are the clay color of the liver, an enlarged spleen with gray-white nodules.

According to the results of laboratory tests, the diagnosis is considered established:

when isolating the culture of F. tularensis from the sent pathological material;

with a positive bioassay with changes in organs characteristic of tularemia and subsequent isolation of a pure culture from them.

In differential diagnosis, tularemia should be distinguished from anaplasmosis, pseudotuberculosis, tuberculosis, paratuberculosis, brucellosis and coccidiosis (eimeriosis) by bacteriological, serological and allergic studies.

In the system of preventive measures, one of the first places is occupied by measures to neutralize the source of the infectious agent, transmission factors and carriers of the pathogen. A decrease in the number of ixodid ticks is facilitated by a change in the timing (late start) of spring grazing, a reduction in the area of ​​natural meadows, grazing on artificial and cultivated pastures, planned or emergency treatments of ticked livestock.

Rodent reduction is achieved by pressing hay and straw into bales; high-quality processing of haystacks and straw throwers with ammonia, transportation of feed immediately after harvest to well-equipped storage facilities that rodents cannot penetrate. It is not recommended to install haystacks and straw along the edges of ravines or forest edges.

Sick animals are not allowed to be slaughtered. In case of slaughter, all products must be destroyed. Products that have come into contact with carcasses, organs or blood of animals with tularemia are boiled.

The export of animals from dysfunctional farms is allowed after the study of blood sera in the agglutination reaction and treatment against pasture mites.

Tularemia- natural focal infectious disease of animals and humans. It is characterized by fever, diarrhea, emaciation, swollen lymph nodes, as well as black phenomena and abortions in animals, in humans - fever, damage to the respiratory tract, lymph nodes, and external integuments.

The causative agent of the disease is a very small microbe, often coccoid with a thin capsule. Motionless, does not form a dispute. Contains antigens associated with its pathogenicity. The causative agent of tularemia belongs to the family of brucellosis bacteria of the genus Francisella.

The microbe is not resistant to high temperatures (at 60 "C it dies in 5 - 10 minutes, at 100 C - within 1 - 2 minutes), but at a temperature of 0 - 4 "C it remains in water and soil from 4 to 9 months, in grain and fodder at 0 "C survives up to 6 months, at 8 - 12" C - up to 2 months; at 20 - 30 "C - up to 3 weeks; in the skins of rodents that have died from tularemia at 8 "C, it remains viable for up to 1 month, at 30 "C - up to 1 week. The microbe is not very resistant to drying, ultraviolet rays, disinfectants: solutions of lysol, chloramine, bleach kill it in 3-5 minutes.

Farm animals are insensitive to tularemia. They become infected from sick rodents in natural foci of this disease. Tularemia is more often hidden in them, accompanied by a slight contamination of tissues with bacteria, microbes are usually not found in the blood and secretions, in connection with this, farm animals do not participate in the natural cycle of the microbe in the foci of the disease.

A person is more likely to become infected from the bites of infected ticks, mosquitoes, horseflies; infection is possible as a result of penetration of the pathogen through skin injuries due to the bite of infected rodents, when skinning, butchering carcasses, etc.; infection is possible through water and food contaminated with rodent secretions, as well as by airborne dust, that is, by inhalation of dust contaminated by the pathogen.

The natural susceptibility of people is very high. The transferred disease usually forms lifelong immunity.

An increase in the incidence of people is observed in the years of an increase in the number of rodents. There are sporadic cases and epidemic outbreaks, which are usually characterized by the predominance of any one of the routes of transmission of the pathogen. Mostly rural residents get sick, becoming infected in domestic (usually when drinking water or products contaminated with the pathogen) or industrial (occupational infection when threshing grain contaminated with rodents, processing vegetables, transporting straw) conditions, as well as hunting, fishing, where there is a risk of transmissible infection . Laboratory infections with tularemia are also known.

The incubation period lasts from 1 day to 3 weeks, usually 3 to 7 days.

Main clinical signs: acute onset. Body temperature rises to 38 - 39 "C and then persists for 2 - 3 weeks. Chills, severe headache, muscle pain, sometimes nausea and vomiting appear. The face and conjunctiva turn red. The liver and spleen are enlarged. The clinical form of the disease is largely determined by transmission of the pathogen, that is, its entrance gate: transmissible and contact infection are accompanied by the development of a bubonic (enlargement of various lymph nodes) or ulcerative-bubonic form; water and food ways lead to an anginal-bubonic or intestinal (abdominal) form; aspiration infection entails development of the pulmonary form with damage to the bronchi or lungs.This variant is characterized by a long and severe course.In case of massive infection, as well as in weakened individuals, a primary septic, or generalized, form is possible.

Preventive measures: the fight against rodents, their destruction in warehouses, barns, dwellings, protection of warehouses and livestock premises from the penetration of rodents.

Scheduled vaccination of the population of territories enzootic for tularemia is carried out with a dry live tularemia vaccine. As a result, the immune layer should be at least 90%. Vaccination is carried out once by the skin method on the outer surface of the middle third of the shoulder. The result is checked on the 5th - 7th day after vaccination, and in the absence of a Y reaction - on the 12th - 15th day. Revaccination is carried out according to epidemiological indications 5 years after vaccination.