Bluetongue (febris catarrhalis ovium) (blue tongue, bluetongue). Bluetongue (bluetongue in sheep). Reference
Bluetongue of sheep ( febris catarrhalis ovium)(" blue tongue", bluetongue) - infectious disease, manifested by a feverish state, inflammatory-necrotic lesions of the digestive tract, tongue and degenerative changes in skeletal muscles.
Etiology. The causative agent, an RNA genomic virus, belongs to the Reoviridae family, the Orbivirus genus.
The particle diameter of the purified cultural virus is 50-65 nm. The virion has a single-layer capsid consisting of 32 capsomeres. Virus particles contain 80% protein and 20% ribonucleic acid. The latter is double-stranded, fragmented (consists of 10 fragments), does not possess infectivity and is not sensitive to RNase.
epidemiological data. Sheep are most susceptible to catarrhal fever, especially young ones. Their sensitivity to the virus depends on the breed. Merinos and their crosses are more sensitive, Karakul and fat-tailed sheep are insensitive. In stationary foci of the disease, sheep of imported breeds are more often affected; locals are more resilient.
Under laboratory conditions, it is possible to infect newborn mice and hamsters, which are injected with the virus into the brain. Cattle and goats are susceptible to the disease, but their disease proceeds without clinical symptoms. However, they can act as a reservoir of the virus during the inter-epizootic period. The disease is seasonal. It appears at the beginning of summer, usually with high humidity, and disappears with the onset of cold weather; not recorded in winter. The highest incidence of sheep is observed in the hot rainy months. The disease is recorded in swampy areas, in areas where there is a lot of rainfall. Sheep usually become infected while on pasture at night.
Inadequate feeding, large crowding in the room, chronic infections, helminthiases, solar radiation aggravate the course of the disease.
Course and symptoms. The incubation period of the disease is 7-10 days, with experimental infection - 2-18 days.
In sheep, acute, subacute, chronic course and abortive form of the disease are distinguished.
The acute course is characterized by a sudden or gradual increase in body temperature to 40.5-42°C. 1-2 days after this, hyperemia of the mucous membranes of the oral and nasal cavities, salivation, outflow from the nasal cavity of serous or purulent exudate, which subsequently dries up with a crust. Edema develops in the ears, lips, sometimes tongue, intermaxillary region, spreading to the neck and chest. The lips become sore, the lower lip droops heavily. On the mucous membrane oral cavity, there are hemorrhages, bleeding erosions, ulcers; due to tissue necrosis comes ichorous smell from the mouth. A swollen and inflamed tongue turns purple or dirty blue and protrudes from the mouth. For this reason, the disease was previously called blue tongue. Often in sick animals, the neck is bent, hair falls out, in severe cases appears bloody diarrhea. Lack of appetite, specific muscle lesions lead to severe exhaustion, weakness, deep asthenia.
In the subacute and chronic course of the disease, all symptoms develop slowly and are less pronounced. Characterized by the exhaustion of animals, dryness and hair loss, damage to the limbs, accompanied by lameness. Sometimes there is a collapse of the horn shoe and bronchopneumonia caused by a secondary infection. The duration of the illness with acute course 30-40 days, with chronic - up to a year. Animals recover slowly. Sometimes, after an apparent recovery, death occurs. Abortive form manifested by a slight increase in body temperature, quickly passing hyperemia of the mucous membranes of the oral cavity. Other symptoms of the disease do not develop. This course of the disease is observed in sheep of more resistant breeds, in large cattle and goats after vaccination.
Diagnosis. The diagnosis is made on the basis of epidemiological data of clinical signs, pathological changes and laboratory results.
Isolation of the virus (from the blood, spleen, lymph nodes) is carried out in the culture of kidney cells of lambs or hamsters, in chicken embryos, which are infected intravenously, as well as in mice with intracerebral injection.
The bioassay is placed on two sheep, previously serologically tested for the absence of complement-fixing antibodies to the bluetongue virus; they are injected intravenously with 10 ml of the blood of a sick animal, a suspension prepared from the organs of dead sheep, or a virus isolated in cell culture or in chicken embryos. A characteristic for catarrhal fever of sheep is an increase in temperature to 41 ° C and above on the sixth to eighth day after infection followed by the development of clinical signs of the disease. In all cases, the isolation of the virus is confirmed by serological methods (RDP, ELISA, MFA, RSK, RN, RNGA).
Differential Diagnosis. It is necessary to exclude foot and mouth disease, contagious pustular dermatitis (ecthyma), smallpox, vesicular stomatitis, malignant catarrhal fever, necrobacteriosis
Treatment not developed.
Prevention and control measures. Recovered sheep acquire lifelong immunity to the type of virus that caused the disease. Reinfection with another type of virus is possible during the same season or the next year. For prophylaxis, a cultural vaccine is used, as a result of which the animal is immune for a year.
Lambs born to immune ewes have passive colostral immunity lasting up to three months.
infectious catarrhal fever not registered in the Republic of Belarus. Emphasis should be placed on strict controls on the importation of animals.
Rosselkhoznadzor detected the bluetongue virus in Russian cattle (cattle) in a five-kilometer zone around the farm in Smolensk region, in which earlier this year the same virus was detected in cattle imported from Germany, follows from the message of the department.
Bluetongue (bluetongue) is a viral transmissible disease of ruminants characterized by inflammatory-necrotic lesions of the oral mucosa, especially the tongue, gastrointestinal tract, epithelium of the corolla and the base of the skin of the hooves, as well as dystrophy, changes in the skeletal muscles.
For the first time, bluetongue was registered in South Africa in 1876, and at the beginning of the 20th century, this problem was considered relevant only for the countries of the African continent. However, the disease has now been reported on all continents. Some of the latest reports of outbreaks of bluetongue in sheep and cattle come from the Netherlands, Belgium and Germany.
The causative agent of the disease is an RNA-containing virus of the Orbivirus genus of the Reoviridae family.
Sheep, especially lambs, are most susceptible to bluetongue, and to a lesser extent, cattle and goats. Wild ruminants also get sick.
Source of the infectious agent- sick animals. Virus reservoirs have not been established in nature. The disease manifests itself in the form of sporadic (isolated) cases and in the form of epizootics (widespread distribution) involving a significant number of susceptible animals.
The carriers of the bluetongue virus are biting midges of the genus Culicoides, which determines the seasonal and stationary nature of the disease. It appears in early summer, peaks in the hot, rainy months, and disappears with the onset of frost. The disease is recorded in swampy, low-lying areas, in areas with abundant annual rainfall. The course of the disease is adversely affected by inadequate feeding, large crowding of animals, chronic infections, helminthiases, and solar exposure.
The incubation period of the disease- 6-9 days. There are acute, subacute, chronic and abortive course of the disease. In an acute course, the main symptom is a sudden or gradual increase in temperature to 41-42 ° C, accompanied by depression. The duration of the temperature reaction is from 2-3 to 11 days. After 1-2 days, hyperemia (overflow of blood vessels of the circulatory system) of the mucous membranes of the oral and nasal cavities, salivation, serous or purulent discharge from the nose appear; edema develops in the head (ears, lips, tongue), intermaxillary space, spreading to the neck and chest, hemorrhages, bleeding erosions, ulcers on the oral mucosa and due to tissue necrosis putrid smell from mouth.
A swollen and inflamed tongue turns purple or dirty blue and hangs out of the mouth (this symptom is very rare). Poddermatitis develops (inflammation of the base of the skin of the hoof), lameness, neck curvature often appears and, in severe cases, diarrhea mixed with blood, severe exhaustion and weakness.
In an acute course, the disease lasts from 6 to 20 days. Death may occur 2-8 days after the onset of the first symptoms of the disease.
In subacute and chronic course, all symptoms develop slowly and are less pronounced. Characterized by the exhaustion of animals, dryness and hair loss, damage to the limbs, lameness. Sometimes there is a decrease in the horny shoe and bronchopneumonia caused by a secondary infection, abortions in pregnant ewes.
The duration of the illness subacute course 30-40 days, with chronic - up to a year. Animals recover slowly. Sometimes, after an apparent recovery, death occurs.
The abortive course is characterized by a slight increase in body temperature, quickly passing hyperemia of the mucous membranes of the oral cavity, and slight depression. This course of the disease is observed in sheep of more resistant breeds, in cattle and goats after vaccination. In cattle, the disease is sometimes accompanied by necrosis of the oral mucosa and a decrease in milk yield with satisfactory general condition organism.
Recovered animals acquire lifelong immunity to the type of virus that caused the disease. Reinfection with another type of virus is possible during the same season or the next year. Lambs born to immune ewes acquire passive colostral immunity (transmitted from mother's milk) for up to 3 months. For immunization, polyvalent live and inactivated vaccines.
Specific methods of treatment have not been developed.
Prevention and control measures
In disease-free countries preventive actions are limited to prohibition of importation of susceptible animals from bluetongue-prone countries, quarantine of domestic and wild ruminants at points of entry.
In threatened zones and stationary foci of the disease, systematic control of vectors is carried out, grazing is prohibited in the evening; during the period of mass summer, insects drive animals from swampy pastures to drier, higher ones; carry out annual vaccination of animals.
The material was prepared on the basis of information from open sources
Bluetongue (or bluetongue) refers to a group of exotic, particularly dangerous diseases of sheep and domestic and wild ruminants, such as cattle, goats, deer, mouflons, most species of African antelopes and various artiodactyls. Infectious catarrhal fever (Febris catarrhalis infectiosa, bluetongue, blue tongue, CBT) is a viral transmissible disease of ruminants, characterized by fever, inflammatory-necrotic lesions of the digestive tract, especially the tongue, corolla epithelium and base of the skin of the hooves, as well as degenerative changes in skeletal muscles. Pregnant animals may have abortions and the birth of malformed offspring. Clinical manifestations diseases and morphological changes vary depending on the pathogenicity of the strain, individual characteristics and breed of animals, the influence of environmental conditions (meteorological factors, solar radiation, etc.).
Historical background: The disease was first described in sheep in South Africa in 1876, and then in cattle (1933). Taylor 1905 discovered its causative agent. Currently, the disease is registered in 36 countries of Europe, Asia, Africa, North and Latin America, Australia and Oceania. The largest number of outbreaks was noted in South Africa and Israel. For the first time in outbreaks have been reported in India and Malaysia. In Canada, after being free of BT since 1976, this disease reappeared in 1976 - the worsening of the epizootic situation for bluetongue in the countries of southern and central Europe. Outbreaks of bluetongue (BTV serotypes 1, 2, 4, 9 and 16) in sheep and cattle have been reported in Italy, Turkey, Greece, and Tunisia. Losses - more than 1.8 million head of cattle 2006 - BTV serotype 8 - Netherlands, Belgium, Germany, France and Luxembourg 2007 - BTV-8 further spread - UK, Denmark, Luxembourg
The causative agent is an RNA-containing virus belonging to the genus orbivirus of the Reoviriday family. The size of the virion is 68 nm. 24 serovariants are known. The virus is stable in the pH zone 6.5-8.0. Resistant to ether and sodium deoxycholate, sensitive to acetone. In a sick animal, the virus can be detected in the blood, spleen and other organs. The virus is cultivated on mice 1-2 days old, chicken embryos and in cultures of lambs kidney cells, VNK-21, where CPD is manifested.
epidemiological data. AT vivo sheep of all breeds are most susceptible to the pathogen, but merinos are more sensitive. Cases of the disease have also been described in cattle, goats, deer, and antelopes. Cattle are mostly asymptomatic. Infectious bluetongue occurs in the form of epizootics with a large population coverage (50-60 percent of the herd), is characterized by seasonality (warm, wet season) and a more severe course of the disease in animals exposed to solar radiation. Biological carriers of the virus different kinds midges of the genus Culicoides; sheep bloodsucker Melophagus ovinus (mechanical vector). During the inter-epidemic period, the virus persists, apparently, in the body of many species of wild ruminant cattle, among which a long-term circulation of the virus (over three years) has been established. Being the main reservoir of the pathogen, infected cattle ensures the stationarity of epizootic foci of the disease. In insects, transovarial transmission of the pathogen and transmission in the course of metamorphosis have not been established; they apparently do not take part in the preservation of the virus in the inter-epizootic period. In primary epizootic foci, mortality reaches 90 percent, in stationary foci, 30 percent.
Pathogenesis The BTV virus directly affects muscle tissue and internal organs, causing deep changes in the vessels. As a result, violated metabolic processes. Animals get very thin. The disease usually aggravates secondary infection. The highest concentration of the virus was found between the 5th and 11th days after infection in the spleen, tonsils, regional lymph nodes, then in the blood (associated with erythrocytes). After 6 weeks, the virus disappears from parenchymal organs. Neutralizing antibodies circulate in the blood simultaneously with the virus, which is in high titer. In pregnant females, the virus enters the fetus, reproduces in the vascular endothelium, causing hyperemia, impaired permeability and subsequent inflammation. As a result, an abortion occurs or an ugly offspring is born.
Acute The acute course is characterized by short-term fever. Usually the temperature rises to 40.5-42 ° C, the mucous membranes of the oral and nasal cavities turn red, salivation is observed, and bloody mucopurulent outflows from the nasal cavity are observed. Then note the desquamation of the epithelium of the mucous membrane, lips, gums and tongue swell, ulcers appear, stomatitis develops. In some animals, the tongue turns dark red to purple or purple which gave the disease its popular name. Nasal discharges become purulent, dry up around the nostrils, partially block the nostrils and make breathing difficult. Edema extends to the muzzle, intermaxillary space, sometimes to the neck and chest. Pneumonia often develops, diarrhea with blood appears, and skin cracks form. Limbs are affected and lameness develops. The defeat of the oral cavity and gastrointestinal tract lead to exhaustion. After 3-4 weeks, the hair begins to fall out. In severe cases, patients die within 1-6 days from the onset of the disease. Sometimes, after a visible improvement in the condition of patients, sharp deterioration and animals die. This happens 3 weeks or more after the first signs of the disease appear.
Subacute In the subacute course, severe emaciation, prolonged weakness, slow recovery, and sometimes curvature of the neck are noted. The limbs are often affected, lameness is first noted, then purulent processes occur in the hoof area, and the horn shoe falls off. The illness lasts for days.
ABORTIVE Abortive course of the disease is characterized only by fever, superficial inflammation of the oral mucosa. More commonly seen in cattle. Recovery occurs relatively quickly. Anorexia, swelling of the mucous membrane of the eyes, salivation, hyperemia of the mucous membrane of the oral and nasal cavities, and fever are observed in approximately 5 percent of cattle. Ulcers are found on the nasal mirror, lips, gums, limbs, udder and vulva. The tongue is very swollen and protrudes from the mouth. After that, difficult swallowing is recorded. Animals die of thirst and pneumonia. However, more often BT in cattle causes abortions and the birth of unviable ugly offspring.
pathological changes. The corpse is emaciated. The mucous membranes of the oral cavity and tongue are hyperemic, cyanotic, edematous with numerous hemorrhages. The epithelium is sweetened, erosion, necrosis, ulcers on the lips, gums, and tongue are observed. Under the skin in the neck, shoulder blades and back, red gelatinous areas are found. Numerous hemorrhages are noted in muscle tissue, small intestine, myocardium, epicardium, mucous membranes respiratory tract, bladder and ureters.
The stability of the virus in the external environment is quite high. In preserved blood, at room temperature, it is viable for 25 years. At a temperature of 60 C, it dies after 5 minutes. Weak solutions of phenol do not neutralize it. Acids, alkalis, chlorine-containing drugs inactivate the virus.
Diagnosis. The disease is established on the basis of epizootological data (seasonality, association with insect vectors, predominantly affecting sheep, proceeds in the form of epizootics), clinical signs (fever, damage to the mucous membrane of the oral and nasal cavities, swelling of the head, lameness, hair loss), pathological changes ( necrosis of the mucous membranes, erosions and ulcers in the oral cavity and tongue, hemorrhage in the muscle tissue, intestines), as well as, according to the results of a laboratory study, the detection of a virus and the detection of antibodies in recovered animals. The virus is isolated by infecting mice (intracerebrally), chicken embryos (intravenously), cell cultures. To clarify the diagnosis, they resort to setting up a bioassay, infecting a healthy sheep intravenously with blood suspicious of the disease of the animal. In all cases, virus isolation is confirmed by serological methods. Diffusion precipitation in agar gel, RIF, RSK, RDP are group-specific and allow the detection of antibodies to any type of virus; in RN and RPHA, antibodies to the homologous type are detected. Designed enzyme immunoassay for antigen and antibody detection. Bluetongue should be suspected if the animals show fever, inflammatory lesions of the oral cavity, and profuse salivation taking into account the seasonal appearance of the disease during the mass attack of blood-sucking dipterous insects.
differential diagnosis. Infectious catarrhal fever must be distinguished from foot and mouth disease (high contagiousness, characteristic foot and mouth lesions of the oral cavity, udder, limbs, results virological research), contagious ecthyma of sheep (contagiousness, pustular lesions of the mucous membranes and skin, microscopy of smears from pathological material, a bioassay on lambs and rabbits), malignant catarrhal fever (sheep rarely get sick, the disease is mostly sporadic, lesions of the eyes and upper respiratory tract are characteristic), necrobacteriosis (except for sheep, horses, pigs and other animals get sick, chronic , isolation of the pathogen), Ibaraki disease (cattle are sick, the results of virological and serological studies), epizootic hemorrhagic disease of deer (virological and serological studies).
Immunity. Sheep that have recovered from illness acquire long-term and intense immunity only against the type of virus that caused the disease; protection against the heterologous type is weak. Complement-fixing, precipitating and virus-neutralizing antibodies accumulate in the blood. Lambs born from immune sheep remain immune to this disease for 3 months. A vaccine against BT from a strain of the virus modified by successive passages in sheep, as well as from strains of the virus passaged in chicken embryos, has been proposed. Immunity in vaccinated sheep appears after 10 days and lasts for at least a year. Abroad and in our country (V.A. Sergeev et al., 1980) inactivated vaccines have been proposed that are harmless to pregnant ewes and irreversible. Intense immunity and specific antibodies in high titer persist for at least a year.
Prevention and control measures. Infectious catarrhal fever is not registered with us. The main attention is paid to preventing its introduction into our country with imported domestic (sheep, goats, cattle) and wild ruminants. Mandatory is preventive quarantine with, if necessary, virological and serological studies. In an area that is permanently unfavorable for infectious catarrhal fever of sheep, it is necessary to vaccinate a susceptible livestock at least a month before the onset of the disease season. When a disease occurs, vaccination should also be carried out using vaccines against the type of pathogen that caused the disease in this focus. At the same time, measures are taken to protect animals from insect attacks. Restrictive measures are also being introduced.
32 Conclusion. To minimize the risk of introduction and eliminate the possibility of the spread of bluetongue in the territory Russian Federation it is necessary: not to import cattle from bluetongue-prone regions; conduct serological survey on bluetongue of all cattle imported from countries bordering on disadvantaged countries and suspected of being affected by bluetongue. If bluetongue is suspected, immediately inform the state veterinary service of the region about this and send samples of pathological material for testing for bluetongue; when bluetongue appears, act in accordance with the "Temporary instructions on measures to combat bluetongue", approved by the Main Directorate of the Ministry of Agriculture of the USSR on March 27, 1974.
List of references Murueva G.B. “Natural foci of cptaral fever in sheep.” Sheep, goats, woolen business with Balysheva V.I., Slivko V.V., Zhesterev V.I. - “Cultivation of the bluetongue virus in animal cell cultures” with Strizhakov A.A. "Creation of tools for epitomous analysis of structural and non-structural polypeptides of the bluetongue virus." Bulletin of the Russian Academy of Agricultural Sciences Strizhakov A.A. "TF inhibition ELISA method for serological monitoring of Bluetongue". Veterinary with Shoopala Johannes. "Features of the manifestation of infectious bluetongue in Namibia." Veterinary medicine with Zharov A.V., Gulyukin M.I., Barabanov I.I. "Pathological and histological studies in the monitoring system pathological processes in the body of farm animals, birds and fish. Veterinary consultant, 10.-s Strizhakov A.A. "Sandwich method of enzyme-linked immunosorbent assay based on monoclonal antibodies for the detection of bluetongue virus antigens." Agricultural biology with Kolomytsev A.A. "Bluetooth fever of sheep: problems of epizootic monitoring". Veterinary consultant p.4-7.
BLUETONGUE Bluetongue (blue tongue, bluetongue, bluetongue) is a viral transmissible disease of ruminants, characterized by damage to the mucous membrane of the oral and nasal cavities, swelling of the tongue, swelling of the front of the head, fever, and damage to the extremities. In cattle, abortions are possible, the birth of ugly offspring. Under natural conditions, young sheep are most susceptible to the disease, less goats, cattle. It poses no danger to humans. Pigs, horses, dogs are not susceptible. The disease was first discovered in sheep in South Africa in 1876, and in 1905 the pathogen was discovered. In cattle, the disease was described in 1933. The first case of bluetongue registration in Russia occurred in 2007, when infected cattle from the Netherlands were brought to the Nizhny Novgorod farm. Etiology. The causative agent is a double-stranded RNA virus belonging to the genus Orbiviruses of the Reovirus family. There are 24 serotypes of the virus that have a common complement-fixing and precipitating antigens. The virus accumulates in the blood and hematopoietic organs of sick animals and can be transmitted transplacentally to the fetus. The maximum concentration of the virus is observed during the period of fever (3-9 days after infection). In some cases, the virus could be detected in the blood of sheep after 3-4 months, and in cattle - more than a year after infection. Cultivation - The virus reproduces in many cell cultures, in chick embryos and in newborn mice. The causative agent is stable in the external environment. In a blood sample, in a preservative solution, stored at room temperature, it remains viable for up to 25 years. Weak solutions of phenol do not inactivate the virus. At t 60 °C, the virus dies within 5 minutes. The virus is rapidly destroyed in acidic environment(pH below 6) and well preserved in alkaline (pH 8-9) Epizootology. sheep are most susceptible, and to a lesser extent cattle and goats. Of the wild animals - white-tailed deer, snow and bighorn sheep, antelopes and moose. Source - the main reservoir of the virus is cattle. This type of animal is more attractive to biting midges compared to sheep. Transmission factors of the pathogen - Transmission of the pathogen is possible only with the help of blood-sucking insects. Major carriers different types midges of the genus Culicoides, in salivary glands which the pathogen replicates. Virus replication in biting midges - 3 days at 300 C, 12-13 days at 200 C, more than 300 C - high death of biting biting. In addition to midges, mosquitoes, mosquitoes, and some types of ticks are carriers of the pathogen. Of the direct methods of infection, sexual transmission of the virus is possible; intrauterine infection has also been noted. Cattle are a natural reservoir of infection. Cows (especially adults) often carry the disease into mild form without significant clinical changes. Bluetongue is characterized by seasonality, which is associated with the mechanism of transmission of the pathogen. The peak of infection occurs during the summer period of blood-sucking insects, the number of infections decreases in dry years. The disease is more widespread in areas with developed bolt and river systems. Course and symptoms The incubation period can last from 5 to 20 days. The course is observed: acute (sheep, deer), subacute (cattle, sheep in enzootic regions), asymptomatic (common in other animal species) forms. Clinical signs may vary by animal species, but nevertheless, the disease in small cattle is more severe than in cattle: temperature rises to 42 degrees in the first days of the disease; - mucous membranes are edematous, reddened; -from mouth frothy saliva is released, putrid smell; - there is a bilateral purulent discharge from the nasal passages; - swelling in the intermaxillary space, head, chest; - hemorrhages on the conjunctiva; - found on the oral mucosa ulcerative lesions; - respiratory disorders; - the tongue is enlarged in size, acquires a purple color, often hangs down (which is interesting "blue tongue" rare sign diseases). Pathological changes Dead animals - exhausted. Edema is noted lower divisions body (breast, intermaxillary space). The mucous membranes are inflamed, have a juicy texture, cyanotic color, with areas of hyperemia. Typical is the defeat of the oral cavity - the tongue is greatly enlarged, often falls out of the mouth and has a blue tint. on the gums and inner surface cheeks - erosion, weeping ulcers. skeletal muscles impregnated with exudate, there are extensive foci of tissue death. The myocardium is loose, the heart itself is enlarged, dropsy is often found, on the epicardium petechial hemorrhages. The defeat of the respiratory system is not typical, signs of bronchopneumonia occur due to concomitant diseases. Diagnosis Based on epizootological, clinical pathological, data, laboratory tests and bioassays. use serological methods- neutralization reaction linked immunosorbent assay. Rarely used PCR. AT diagnostic center sent samples: spleen, lymph nodes(submandibular, mesenteric) blood and its serum. Economic damage Illness covers big number animals and is characterized by high mortality. When a disease occurs in previously prosperous areas, it is 70-90%, in stationary foci it ranges from 10 to 30%. In Spain, for example, in 1956 the disease swept over 200 farms in 4 months, and more than 130,000 sheep died. Significant damage is also caused by a decrease in productivity, loss of wool in sheep and a violation of the reproductive function. Clinically sick animals are sent for slaughter. Meat is used for canned products, sausages after boiling for 2.5 hours. Prevention and control measures. There are no specific control measures. In order to prevent the introduction of the pathogen into the country, a ban on the import of sheep, cattle and wild ruminants from countries affected by the disease is envisaged. Annual serological survey of sheep, cattle and deer, especially young animals of the current year of birth, on farms located in border areas. When importing susceptible animals from countries with an unexplored epizootic situation or where bluetongue is detected, it is necessary to conduct a thorough serological, epizootological and clinical examination and quarantine on the spot. Carry out disinfection and disinfestation of vehicles arriving from these countries. For disinfection, 3% solutions of formalin or sodium hydroxide are used. When a diagnosis is made (isolation of the pathogen, positive bioassay), quarantine is imposed on the farm, and the surrounding area (within a radius of 150 km) is considered unfavorable. Such a large coverage is associated with the peculiarities of the spread of infection - blood-sucking insects. In the threatened area, more than 0.5% of all susceptible flocks should be clinically examined and bled for serological diagnosis. It is forbidden to import animals into the quarantine area, and it is not allowed to export and drive susceptible species through the affected area. All livestock (large and small cattle) are immediately vaccinated. Clinically sick animals are sent for slaughter. Restrictions are lifted a year after the last case of a case and a subsequent negative laboratory test for the carriage of the virus. Subsequently, on the farm and adjacent territories, it is mandatory to carry out diagnostics and vaccination of livestock.
A viral transmissible disease of ruminants, characterized by a feverish condition, inflammatory-necrotic lesions of the oral cavity (especially the tongue), gastrointestinal tract, corolla epithelium and the base of the skin of the hooves, as well as degenerative changes in the skeletal muscles.
Pathogen. RNA-containing virus Genus Orbivirus is included in the fam. Reoviridae.
spectrum of pathogenicity. Sheep are the most susceptible domestic animals to the BTV virus. Shown, that European breeds more sensitive than African and Asian ones, such as Persian Blacks, Karakul. Lambs born from non-immunized queens are very susceptible to the virus. Cattle and goats are susceptible to the KLO virus.
Sources of infection and routes of transmission. The BTV virus is capable of reproducing in mammals (ruminants) and insects. Under natural conditions, vertebrates become infected through the bites of blood-sucking insects.
CLOUGH - seasonal disease , as it is associated with the periods of summer of midges. Usually, BT occurs in spring and early summer, spreads mainly in river valleys, lowlands, marshy places abounding with biting midges. Sheep grazing in such places, especially in the evening and at night, is associated with heightened danger BT infection. It has been established that cattle lambing is the main host of the TBV virus.
epidemiological data. Under natural conditions, sheep of all breeds are most susceptible to the pathogen, but merinos are more sensitive. Infectious bluetongue occurs in the form of epizootics with a large population coverage (50-60% of the herd), is characterized by seasonality (warm, wet season) and a more severe course of the disease in animals exposed to solar radiation.
Biological carriers of the virus are various species of biting midges of the genus Culicoides; sheep bloodsucker Melophagus ovinus (mechanical vector). In the inter-episoonic period, the virus apparently persists in the body of many species of wild ruminants and cattle, among which a long-term circulation of the virus (over three years) has been established. Being the main reservoir of the pathogen, infected cattle ensures the stationarity of epizootic foci of the disease.
clinical symptoms.
The incubation period is 6-8 days. After the incubation period, there is a rise in temperature to 40.6 - 42.0 °; fever lasts from 6-8 to 12 days. 24-36 hours after the first rise in temperature, hyperemia of the skin of the muzzle, lips, ears, as well as mucous membranes of the oral and nasal cavities develops, accompanied by expiration foamy saliva and peculiar continuous movements of the tongue. Muco-catarrhal discharges appear from the nasal cavity, sometimes with an admixture of blood. The lips and tongue swell noticeably, the muzzle enlarges, becomes darker in color, petechial hemorrhages appear on the mucous membranes of the mouth, nose, and eyes. In a small percentage of cases, the tongue turns red-blue (hence the name of the disease). Hair falls out on the muzzle, erosions form on the mucous membranes of the mouth and nose, which bleed easily. In more severe cases, the mucous membranes of the cheeks, gums and tongue ulcerate and bleed, saliva mixes with blood and necrotic tissues, takes bad smell. Nasal discharges become purulent and dry up in crusts around the nose, causing anxiety to the animals; thirst develops. Because of the pain in the mouth, food intake stops, the animal lies on its side. In cases ending in death, enteritis develops, accompanied by diarrhea. Sometimes at the height of fever, but more often after a drop in temperature, on hind limbs you can see the reddening of the rim of the hooves with elevated temperature and pain on pressure. The redness then turns to blue with dark red foci, followed by irregular regrowth of the hoof with ripples. By the number of these wavy lines, one can judge the number of types of virus that the animal has had. Soreness leads to lameness, unwillingness to move, and staggering gait. The back arches, and the sheep often, driven by hunger, move to the feed on their knees. Inability to feed and muscle damage lead to progressive wasting, accompanied by impaired bowel function. In this state, animals can remain up to 10 days and then until death - in prostration and exhaustion. 3-4 weeks after the fever stops, the hair begins to fall out, hanging in tufts. The duration of the illness varies. Lesions in the oral cavity may heal slowly (depending on the secondary microflora). With a mild course of the disease, a short fever and transient hyperemia of the mucous membranes of the mouth are noted. In an acute course - swelling of the pharynx and paresis of the esophagus can cause severe aspiration pneumonia; in the blood - leukopenia, poikilocytosis, later - anemia. In especially severe cases, hemoglobin and total nitrogen decrease. After the 8th day from the moment of infection, a pronounced increase in γ-globulins and a less pronounced increase in globulins are noted, the level of α1 and α2-tlobulins and albumin is lowered.
In the subacute course, the described signs are less pronounced, changes in the mucous membranes of the head, inflammation of the skin, hooves, exhaustion, hair loss, death can occur only after a year.
With an abortive course (sometimes), which is possible after vaccination, there is a slight fever, mild hyperemia of the mucous membranes without ulceration, appetite is preserved.
In cattle, TBT occurs in most cases as a latent infection, especially in enzootic zones. At the initial onset of the disease, symptoms resembling foot-and-mouth disease and TBV in sheep have been described. Recently there have been reports of abortions and the birth of malformed, dwarfed and underdeveloped calves.
pathological changes. At autopsy, the following changes are found: subcutaneous tissue and muscle connective tissue are edematous, impregnated yellowish color liquid. The tissues of the lips, tongue, ears, pharynx and larynx, intermaxillary region are also edematous, chest. The edematous fluid sometimes acquires a reddish color from the admixture of blood or a gelatinous consistency. In the chest and abdominal cavities, in the pericardium, there may be an accumulation of edematous fluid.
If the animal fell into acute period diseases, the most pronounced changes are observed in digestive system: the mucous membrane of the mouth is hyperemic, edematous, cyanotic, covered with hemorrhages of various sizes and shapes. On the lips, tongue, inner surface of the cheeks, ulcerations, sometimes extensive, covered with dirty grayish necrotic masses through which blood seeps. In the scar and mesh, in the abomasum, hyperemia and hemorrhages are observed, most pronounced on the papillae and leaflets. The gutter of the esophagus may be hyperemic, covered with ulcers and even foci of necrosis. The mucous membrane of the abomasum is diffusely hyperemic, sometimes cyanotic and covered with hemorrhages of various shapes and sizes. In the small intestine, inflammatory changes vary from focal hyperemia to a catarrhal process throughout (to the thick section). nasal cavity filled with dirty yellow catarrhal contents from the nose. The nasal septum is edematous, filled with blood and covered with ulcers. The trachea contains a foamy fluid that appears with edema or congestion of the lungs.
Changes vascular system characterized by hyperemia of all tissues, edema and hemorrhage. There is a small amount of fluid in the cardiac shirt, as well as hemorrhages under the epicardium and endocardium. In the medial layer at the base of the pulmonary artery in acute cases, as a rule, hemorrhages. Sometimes in the papillary muscle of the left ventricle, foci of necrosis are found, which can spread throughout the heart muscle.
The spleen and lymph nodes are usually only slightly enlarged. The most frequently affected are the pharyngeal, cervical, mediastinal, maxillary, bronchial, mesenteric, prescapular, sublingual lymph nodes, which in this case are enlarged, reddened and edematous. In the liver venous congestion and degenerative changes. In the kidneys - hyperemia, edema.
The main changes with the greatest constancy occur in the skin and muscles. Sometimes lesions on the skin of the muzzle and the rim of the hooves are limited only to redness. More often, redness on the corolla is replaced by the appearance of pinpoint foci, which merge and form vertical reddish stripes in the substance of the horn. These changes are more often seen in the hind limbs.
Changes in the muscles are expressed by edema of the intermuscular connective tissue and fascia with a reddish gelatinous fluid. The muscles of the thighs, shoulder blades, back, and sternum are often affected (Moulten, 1961). They reveal small (1-2 mm) hemorrhages, as well as foci of necrosis. Degenerative changes in the muscles are sometimes so deep that the muscles acquire a grayish tint and become like boiled.
Diagnostics. The diagnosis of BT is made on the basis of epizootological, clinical, pathological and morphological data and laboratory results.
Of the epizootological data, the appearance of the disease in a hot rainy period, a simultaneous increase in the number of blood-sucking insects, the nature of the terrain (lowlands, wetlands, river valleys, etc.), the presence of an imported contingent (from safe zones) of animals are important.
Of the clinical symptoms, fever, depression, cyanosis of the tongue, lips, gums, swelling of the muzzle, curvature of the neck, lameness are important. Their severity can vary over a very wide range.
Of the pathological changes deserve attention. exhaustion, swelling of the subcutaneous and intermuscular connective tissue, degenerative changes in skeletal muscles, necrosis of the mucous membranes of the mouth, tongue, lips, etc.
The presence of these signs and the detection of antibodies to the BTV virus in the blood of animals by means of CSCs make it possible to put provisional diagnosis for bluetongue in sheep.
The final diagnosis is based on the results of experimental infection of sheep, isolation and identification of the virus. The virus can be identified:
1) from whole blood obtained during a fever;
2) from the spleen;
3) from lymph nodes (especially mesenteric, taken in the acute stage of the disease). Material for virus isolation is taken into Edington's preserving liquid. To isolate the virus, either 6-8-day-old chicken embryos or cell cultures (PYa, VNK-21, L, BEP, etc.) are infected with pathological material > or suckling mice (intracerebrally), or sheep (the most sensitive object). As a rule, the virus is isolated after several blind passages. Even on sheep, it is sometimes necessary to carry out 2-3 passages.
To differentiate the isolated virus from other viruses, CSC is used, and for typing, a neutralization reaction is used. RSK in TBT is group-specific and can be used to detect antibodies to any strain of the TBT virus. RSK is used for serological reconnaissance of the area for the circulation of the BTV virus in it. The neutralization reaction is used to study immune status animal and for typing the isolated virus. top scores obtained by prolonged (24 hours) contact of the virus with serum at a temperature of +37°.
A quick result is obtained by using the method of fluorescent antibodies with a culture of infected cells. Specific luminescence Detected already in the 1st passage of the virus in cell culture, when there is no CPE yet. In addition, specific inclusion bodies can be detected in the infected cell culture already in the 1st passage.
differential diagnosis. Infectious catarrhal fever must be distinguished from foot and mouth disease (high contagiousness, characteristic foot and mouth lesions of the oral cavity, udder, limbs, results of virological studies), contagious ecthyma of sheep (contagiousness, pustular lesions of the mucous membranes and skin, microscopy of smears from pathological material, bioassay on lambs and rabbits), malignant catarrhal fever (sheep rarely get sick, the disease is mostly sporadic, lesions of the eyes and upper respiratory tract are characteristic), necrobacteriosis (except for sheep, horses, pigs and other animals, chronic course, isolation of the pathogen), Ibaraki disease (cattle are sick, the results of virological and serological studies), epizootic hemorrhagic disease of deer (virological and serological studies).
CBT must be differentiated from the following diseases:
Hydropericarditis. (Extremely dangerous non-contagious disease of sheep caused by Ricketsia ruminantum and transmitted by ticks of the r. Amblioma. It is characterized by fever and nervous symptoms. Distributed in the same areas of Africa as KLO. With CL there are no nervous phenomena, the fever is longer, the course is slower, and it is not amenable to antibiotic therapy.
Rift Valley Fever. Mortality in sheep up to 100%, calves - 70-100%, abortions. On autopsy, necrosis and degeneration in the liver, acidophilic inclusions in the liver cells.
Differentiation from KLO according to RA, MFA, RSK, RZGA.
Sheeppox. Lesions of the skin and mucous membranes of the mouth,
respiratory tract, gastrointestinal tract. With K. LO - lesions only in (oral and nasal cavities, lack of contagiousness.
Contagious ecthyma of sheep. Formation of papules and vesicles on the lips and nostrils, sometimes around the eyes. They are replaced by pustules and a thick crust, are not accompanied by edema and hyperemia of the mucous membranes, which is typical for CL. Difference from KLO and epizootology.
FMD. Lesions develop rapidly, cover a large percentage of animals, the disease is highly contagious, there is aphthae. There is none of this with KLO.
"Weeping disease". This disease occurs in calves aged from 1 week to 6 months, is transmitted by ticks, is characterized by stomatitis, hyperemia of the mucous membranes and skin with the development of wet eczema. Diphtheria often develops in the mouth and pharynx. The disease is not transmitted with blood to sheep, it is characterized by a severe course and lethality.
Vesicular stomatitis. Can be differentiated from CLO by epizootology. Horses get sick too.
Three-day disease of cattle. (Stiffsickness - stiffness of movements). Manifested by lameness, stiffness of movements, paresis (pass quickly), high fever(passes quickly). There is no hyperemia, it is not transmitted to sheep (like KLO).
Immunity and prevention. Recovered sheep acquire lifelong immunity to the type of virus that caused the disease. Re-infection is possible during the same season or the next year, but only if infected with a different type of virus.
Annual vaccination is recommended, since post-vaccination immunity is established after a year, but how long it lasts is not known. To avoid post-vaccination complications, mass vaccination is recommended after sheep shearing.
Vaccination of pregnant queens is avoided, as attenuated strains cause abortions and the birth of malformed lambs. Vaccination of breeding rams can cause their temporary sterility, so rams are vaccinated after the mating season. Lambs born from immune queens remain immune until 3-6 months of age and during this period do not respond to immunization with the vaccine.
For immunization use: vaccine against bluetongue (bluetongue) cultural inactivated (VNIIViM), mono- and bivalent inactivated sorbed vaccines, etc.
Treatment. Currently no medicines, specifically acting on the BTV virus in vivo. The success of the use of antibiotics and sulfonamides is explained by their effect on secondary infection, especially in the development of bronchopneumonia.
Careful care of sick animals is the most important measure. Sick animals must be placed in rooms protected from direct sunlight. A small amount of tender green fodder at a time when lesions on the oral mucosa cause pain when eating, improves the condition of animals. Superficial lesions moistened with disinfectants, make alcohol lotions. During the recovery period, it is most important to maintain and, if necessary, stimulate the activity of the scar. Careful and good feeding and care helps to shorten the recovery period and restore normal condition.
Control measures. Infectious catarrhal fever is not registered with us. The main attention is paid to preventing its introduction into our country with imported domestic (sheep, goats, cattle) and wild ruminants. Mandatory is preventive quarantine with, if necessary, virological and serological studies.
In an area that is permanently unfavorable for infectious catarrhal fever of sheep, it is necessary to vaccinate a susceptible livestock at least a month before the onset of the disease season.
When a disease occurs, vaccination should also be carried out using vaccines against the type of pathogen that caused the disease in this focus. At the same time, measures are taken to protect animals from insect attacks. Restrictive measures are also being introduced.
At present, there is no internationally accepted regulation for the control of BT. The International Epizootic Bureau has developed only the following basic principles for preventing the introduction of BTs into safe countries.
1. Prohibition of the importation of sheep, goats, cattle and wild ruminants, as well as their semen, blood and serum from countries (or foci) unfavorable for BTV, into the zones free from BTV.
2. Destruction of BTV vectors for all vehicles(ships, planes, cars, trains, etc.) arriving from countries (foci) that are disadvantaged by the KLO.
3. When importing susceptible animals from countries considered free from BTV, it is necessary to require the presentation of an international veterinary health certificate certifying that the imported animals are from a BTV free zone (country), that they have undergone a 40-day quarantine and have been subjected to diagnostic tests.
4. Animals imported from other countries must be quarantined for 30 days. During the quarantine period:
a) daily clinical examination and thermometry;
b) a study in the RSK of blood sera for the presence of antibodies to the BT virus;
c) pathological material (blood, affected muscles) is taken from animals suspected of having a disease for virological and pathological morphological studies.
In case of detection of animals with TB disease or virus carriers, the entire group of imported animals is killed using meat for canned sausages.
5. When a KLF is established on a farm, a settlement with allotted pastures is declared unfavorable, quarantine is imposed on it and the following measures are taken:
a) It is prohibited to export domestic and wild ruminants to other holdings;
b) It is prohibited to export semen, blood and serum from domestic and wild ruminants;
i) All transport that goes beyond the disadvantaged area must be treated with insecticides;
d) For unfavorable flocks of sheep, constant veterinary supervision is established. Sick sheep are isolated, exposed symptomatic treatment and treated with insecticides.
e) Premises, pens where unsuccessful flocks were kept, as well as slaughter sites must be disinfected: with a 2-3% solution of sodium hydroxide, sodium hypochlorite solution, bleach or 2% formaldehyde solution.
f) During the period of insect activity, it is necessary to keep sheep on elevated pastures, and drive them into the premises at night and free them from "insects.
6. Slaughter and use for meat of sheep with BT is allowed within disadvantaged areas with the permission of the veterinary authorities.
When present in muscles degenerative changes, gelatinous infiltrated connective tissue in the intermuscular spaces, redness of the internal and subrenal fat, hemorrhages in subcutaneous tissue whole carcasses are sent for technical disposal.
7. Skins obtained from the slaughter of sick animals or taken from corpses are neutralized by rubbing with a curing mixture containing 83% table salt, 7.5% ammonium chloride and 2% soda ash, followed by storage and holding for at least 10 days.
8. In disadvantaged areas (center), all sheep are subjected to preventive vaccination:
adult sheep - 3-4 weeks before the start of mating;
rams-producers - after mating;
lambs - upon reaching 5 - 6 months of age.
Vaccinated animals are kept in cool places protected from the sun, insects and ticks for 10-14 days after vaccination.
9. Sale, exchange, transfer to other farms of domestic and wild ruminants from disadvantaged areas are prohibited.
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