Despite the fact that tuberculosis in cows and humans was identified and described in detail more than 150 years ago, to this day, this disease remains one of the most dangerous. To successfully deal with it, you need to understand where it comes from and how it is scary. Therefore, we will further analyze the strains of the disease, its nature, methods and methods of diagnosis and, of course, means of preventing and treating tuberculosis in cattle.
A bit of history
The first mentions of signs of tuberculosis are found in the IV century BC. At that time, Hippocrates described common clinical symptoms and reactions to the disease in humans, plus gave recommendations for treatment.
The term itself was introduced into circulation by a French doctor by the name of Lenek around 1819. Researcher Willemen in 1869 proved that the disease is infectious. It can quickly take the form of an epidemic.
In 1882, the German scientist R. Koch identified and described a microorganism that is the main causative agent of the disease, after which it was called the Koch wand. The same Koch conducted the first serious diagnostic studies, with the result that in 1890 tuberculin was born, giving a reaction to tuberculosis.
Detection of bovine tuberculosis is attributed to 1828, but the signs and symptoms were described only in 1895 and were called by the name of the researcher, Ion's paratuberculosis enteritis.
The microorganism Mycobacterium tuberculosis, which causes the disease, is an aerobic, non-spore acid-resistant microorganism. The reading or visualization can be shown in the form of straight or slightly rotated sticks with different angles of 0.5 - 8 microns in size. Sometimes there are round shapes lined up in a beaded chain. There are practically no single individuals in the colonies.
There are 3 types of the causative agent of tuberculosis in cattle, more precisely, 3 forms of the same microorganism that lead to infection with tuberculosis - the human form, bull and bird. But the problem is that these forms of the disease can be reborn and masked. So, for example, the human wand can be found in a cow, and the avian strain in pigs. We list these forms:
- "Mycobacterium tuberculosis" (human strain) - cattle, pigs and fur-bearing animals can get sick. In cats or dogs, it is less common;
- "Mycobacterium bovis" (bovine strain or paratuberculosis) - cows are the main carrier, easily transmitted to humans, plus all wild as well as domestic mammals;
- "Mycobacterium avium" (avian strain) - except for birds, this strain is sometimes found in pigs.
How are cows infected?
Paratuberculosis in cows is transmitted through sputum, various kinds of mucous discharge or feces. Also in cows milk is a strong source of infection. The infection can stay in the body of cattle for a long time without showing itself, that is, in a dormant state.
In addition, infected pastures, soft bedding on farms and manure can become contagious factors. Calves paratuberculosis is transmitted mainly when they drink milk from infected cows, as well as through the reverse.
Identifying the disease often makes it difficult to have a long incubation period. In cows, paratuberculosis may not appear from 2 weeks to 3 months. Cases were recorded when a healthy-looking animal had been a carrier of the disease for years. At the same time infecting everyone around her, the cow herself felt good.
If there are clinical manifestations, it means that the cow has been infected for at least 2 weeks. Regular farm tuberculinization has now become the norm, because the first symptom of the disease in a cow is a positive, pronounced individual reaction to tuberculin.
There is an open (active) form of the disease and a closed one. In the case of the open form, the wand can be sown everywhere. It comes out with sputum, feces may come out, milk shows a positive reaction, even sperm in bulls may contain Koch's wand. Closed paratuberculosis in cows will show only in-depth laboratory research, and then not always.
The pulmonary form of the disease is manifested by a strong, hacking cough with fever and mucous, purulent discharge from the nose.
With the defeat of the udder, the lymph nodes are enlarged and thickened above it. Watery, sometimes curdled, milk with blood splashes appears. Serous integuments of a cow (pearl oyster) may be affected.
Pathological manifestations of the disease
In case of tuberculosis, an autopsy of cows is carried out exclusively in the laboratory with all the required safety standards.
Often on the internal organs of cows, the disease is manifested by the presence of malignant nodules and formations of a grayish color with a yellow tinge. Their sizes can be different, from a small millet seed to a tumor bigger than a chicken egg.
Malignant formation has a layered structure. In the center observed curdled necrotic masses. In most cases, the paratuberculosis site is encapsulated, that is, covered with dense tissue in which calcareous compounds are present.
The lung tissue of cows is affected by 99%, the liver suffers a lot, lesions of the mammary glands in case of disease can reach 10%. In the lymphatic system of cows, the pharyngeal, mesenteric, cardiac, bronchial, supra elevated, hepatic and pre-lobe lymph nodes are affected.
Subtleties of diagnosis
According to the rules of the diagnosis of the disease in herds of cattle spend complex. Specialists are based on the results of a number of allergic, histological, epizootological, pathological, bacterial and biological tests. In addition, the clinical signs of the disease are taken into account.
It is known that at the initial stage, immediately after the initial infection of cows, the response to the diagnostic drug in animals is rather weak. The level of sensitization increases gradually with the development of colonies of Koch sticks in the body.
Moreover, in suspicious and stably positive herds, the response to traditional tuberculin and other types of diagnostics is significantly lower than in newly infected herds. This paradox is caused by the manifestation of allergies in many cows. And also by the fact that some cows in positive herds are beginning to actively produce anti-tuberculosis antibodies.
In this case, cows are injected with PPD of tuberculin intended for mammals. Diagnostics can begin animals older than 2 months, and the breeding stock is also diagnosed, regardless of the time and period of pregnancy.
Allergy testing of animals is not carried out only for 22 days after vaccinations against other dangerous infectious diseases.
The preparation for cattle is injected exclusively intracutaneously. Cows and calves are injected into the middle third of the cervical region, and insemination bulls are prickled into any of the folds under the tail. It is possible to evaluate the first signs only three days after the injection.
There is also a tuberculin ophthalmoprobic (eye). But in cows, it is used only in combination with a subcutaneous, plus eye ophthalmoprobin, it is advisable to make cows not younger than 6 years. The preparation is instilled twice, it is necessary to drip with an interval of 5-6 days, the lower eyelid is delayed and the preparation is buried in the cornea.
This method can also be called ocular in part, because the injection is done in the cow's eyelid, palpebral. This method helps to more accurately study the paraspecific reactions of the cow during the initial diagnosis of the herd. The injection is made in the lower eyelid, for this you need to retreat from the edge of the eye about 15-20 mm. The standard dose is 0.2 cube.
Palpebral method is also assessed as allergic, that is, three days after the introduction of the diagnostic drug to the cow. The reaction is considered positive if a noticeable tumor has formed at the point of injection, or the eyelid is completely inflamed.
Palpebral test gives a high rate of detection of the disease when a cow is infected with bovine or human strains. If an apathetic microbacterium is identified in a cow, they will not respond to the palpebral sample.
It is used when the primary diagnosis of tuberculosis of cattle is carried out, and it gave a positive result in a successful earlier herd. In this way, individuals are selected for slaughter, with the aim of more accurate autopsy and biological analyzes.
It also uses tuberculin designed for mammals, but it needs to be diluted in half with saline. The dosage is taken in proportion to 1 ml of solution per centner of live weight of the cow.
The reaction of the cattle is checked after 3 hours, then after 6 hours and a control check after 9 hours. First of all, the temperature is measured - a deviation from the norm of 0.9 C is considered critical. In addition to temperature, there is a general condition of the cow. Infected cows show marked apathy, the pulse quickens and shortness of breath appears.
If the tuberculin solution is administered intravenously to an animal with the active phase of the disease, then the cow will experience a shock, which often ends in death. At the opening of these cows revealed multiple swelling and hemorrhage.
This type of diagnosis is considered to be the most accurate, but a complete, extensive laboratory analysis can be done only after the animal is opened. Samples are taken from the lymph nodes. The list of mandatory for research includes:
In addition, sections of parenchymal organs are sent to the laboratory, in particular, the lungs, liver and spleen of the cow. It is desirable that these sections were with traces of disease. Milk is also sent for research.
Samples and material sections are delivered to the laboratory in fresh or frozen form. Laboratory analysis for such diseases is carried out within 3 months after the selection of the material.
Disease prevention in safe herds
All such activities are carried out in accordance with veterinary instructions, which were approved on 06/18/1996.
Tribal and newly arrived cows must be placed on a monthly quarantine content. During this period, it is necessary to carry out a comprehensive diagnosis of the state of the cow, one of the main activities is to check for the presence of Koch's wand.
The return, intended for feeding calves, must be pasteurized. Due to the similarity of strains, carriers and people with an active form of the disease it is strictly forbidden to work on farms.
According to the rules, a herd is examined at least twice a year. In the spring - in before sending on summer pastures, and also in the fall - during preparation for the winter maintenance. Cows that are kept on private farms are checked one time at the same time that similar activities are held on large farms.
If Koch sticks were found in the carcasses sent to the meat processing plant during acceptance, all prosperous farms in the area, and with them the private farmsteads, should be examined by veterinarians within 2 months. This is done to confirm or deny mass infection.
Fighting disease in disadvantaged farms
A farm, locality or individual herd is declared unfavorable by decree of the regional or district administration on the proposal of the chief veterinarian. After that, a complex of various restrictions is introduced to prevent the spread of the disease.
According to 1996 VetsanPin, the improvement of cattle livestock enterprises can be done only in two ways. The first involves checking livestock about 1 time in 2 months. By results of check the revealed sick cows are destroyed. At the same time, it is impossible to drink milk and eat cows meat with obvious suspicion of the disease.
According to the second method, the entire herd is cut out completely, and in its place healthy young animals are imported. But before updating it is necessary to carry out a number of different kinds of events.
Activities involving a complete replacement of livestock
The decision to complete, one hundred percent replacement of the herd can be made in those farms where the disease is detected for the first time, as well as in the event that the herd is infected with more than 15% of cows.
After the decision is made, allergic diagnosis is stopped. Insemination of animals can not be carried out. All milk produced during this period must be pasteurized at a maximum temperature of 90 C in such cases, the duration of pasteurization must be at least 5 minutes.
Regardless of the presence or extent of the disease, all the livestock, along with the young stock, should be surrendered within six months.
Barns and nearby areas are treated with a solution of formaldehyde in a concentration of 3% with the addition of caustic soda (1 liter of solution per 1 square meter).
The soil is removed and mixed with lime on the spade bayonet. Dung piles take out and all poured lime. Wooden floors are torn down and burned.
Tuberculosis is one of the most dangerous diseases in the history of mankind. If, in your opinion, the material was useful, then share it with your friends, perhaps your likes will save some household from this scourge.
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