Tuberculosis (Tuberculosis) is called a serious illness of a chronic nature that affects humans and many species of animals. It is characterized by tubercles - specific nodules that form in different organs with subsequent caseous necrosis and calcification. The topic of today's article is animal tuberculosis (symptoms and treatment).
What is this disease?
She has been known since ancient times. A description of its signs is found in the writings of Hippocrates as far back as the 4th century BC. e. In 1882, R. Koch was able to solve the problem of identifying the causative agent of this serious illness, and he later produced tuberculin. BCG vaccine appeared in 1924 and still serves as a specific prevention of human tuberculosis.
Animal tuberculosis is found in most regions. One can speak about its almost complete elimination only in developed European countries and the USA. Because of this disease, animal husbandry suffers significant economic losses due to a drop in productivity, unplanned culling and sending sick individuals for slaughter, as well as the need for serious costs for expensive anti-epidemic measures.
Who is the causative agent
Mycobacteriumtuberculosis - under this name there is mycobacterium, in the genus of which there are more than 30 different types of microorganisms. Some of them are non-pathogenic, others are pathogenic, that is, capable of causing diseases. Three species from the category of the latter are especially dangerous.
The human species leads to disease in humans. In addition, dogs, cats, pigs and cattle are susceptible to it. He is also able to hit fur-bearing animals. Birds (with the exception of parrots) are not susceptible to it.
A type of tuberculosis, called bovine, can cause tuberculosis of animals and humans. Moreover, it affects not only agricultural cattle, but also wild animals. Only birds retain immunity in this case.
The bird species can also affect pork stock. Cases of infection of humans or other animals are very rare.
Tuberculosis bacilli (mycobacteria) of each of the listed species are quite similar. They can be found in smears in groups or singly. In addition to tuberculosis, there are also opportunistic mycobacteria. In the case of infection of animals with them, a similar reaction to a specific test is possible, due to which the diagnosis of tuberculosis in animals can be difficult.
The resistance of mycobacteria to chemicals and various external factors is very high. In soil or manure, it can be stored in a viable form for up to 4 years or more. The corpses of cattle and dead birds serve as a repository of mycobacteria from 3 months up to a year. For a long time, the causative agent of animal tuberculosis can exist in products (milk, butter, cheese, meat) obtained from sick animals.
Which animal is more likely to have tuberculosis?
Most of the wild and domestic representatives of the fauna are susceptible to it (over 55 species of mammals and 50 species of birds). Hypersensitivity to animal tuberculosis is characteristic of cattle and pigs, as well as chickens. Much less often, cases are found in cats, dogs, geese and ducks, and only as an exception in sheep, horses and donkeys.
The source is considered sick animals, the allocation of mycobacteria from the body of which occurs with milk, sputum, feces. Once in the body, the pathogen is able to persist in an undiagnosed form for a long time. Such individuals can serve as hidden sources of the disease.
What are the main causes of animal tuberculosis? Once in certain conditions, this form of mycobacteria reverses into its classical form and leads to the onset of the disease.
Distribution paths
Tuberculosis of farm animals is transmitted through food, water, litter, contaminated with secretions of already diseased individuals. The defeat of young animals occurs mainly through milk. From a sick mother, calves can become infected in utero. Cases and transmission of tuberculosis in contact with sick people (calves, milkmaids) are not excluded. In the stall period, the path of infection of adult cattle is aerogenic. In summer, the pathogen can be transmitted on open pastures.
Defeat pigs is possible in the process of feeding kitchen waste received in hospitals and tuberculosis dispensaries and not subjected to disinfection. The way of infection of cats and dogs is when feeding milk or meat from sick cows.
Resistance of the animal organism is an important factor affecting the rate of mass spread of the disease. With its reduction, the epidemic can take on alarming proportions. This happens in cases of malnutrition, lack of important trace elements, amino acids and vitamins in the diet, a small amount of exercise, dampness and crowded rooms and unsanitary conditions.
How does the disease occur?
Once in the air or when feeding into the body, mycobacteria of animal tuberculosis end up in the lungs or other organs with a blood or lymph flow. In places of their localization, inflammation and the formation of tuberculosis (tuberculous nodules) occur. They have a rounded appearance and a grayish color, the size - with lentil grain.
Dead cells inside the tuberculum take the form of a curd mass. If the disease proceeds benignly, the primary lesion calcifies and, surrounded by connective tissue, does not lead to the progression of the disease. In cases of reduced resistance, the walls of the tuberculous nodule allow mycobacteria into the external environment. Once in healthy tissue, they form many other such foci and sometimes merge into entire large areas affected by tuberculosis.
Getting from them into the blood, mycobacteria are spread to various organs in which foci of various sizes appear. In the case of extensive lesions, the disease easily leads to exhaustion and death.
How to detect tuberculosis in animals
The incubation period of this disease is 2-6 weeks. In connection with the possible latent or chronic course of the disease, it is possible to detect the first clinical signs of a lesion only months or even years after infection. Diagnosis of tuberculosis in animals exists mainly in the form of one of two methods - allergic and serological. Clinically expressed forms already speak about a rather long course of the disease. They can be diverse even among representatives of the same species.
The pathological process can be localized in the pulmonary or intestinal form, as well as some others. There may be cases of generalized tuberculosis. With lung damage in cattle , the course of the disease most often occurs in a chronic form. Acute and subacute developmental options are found in young animals.
Animal Tuberculosis - Symptoms
It is possible to determine the disease in the lungs in animals by a strong, dry cough with an increase when standing up or in cold air. Temperature increase is possible up to 39.5-40 ⁰. Productivity, like appetite, is not reduced at the initial stage.
When the disease progresses, signs of lung and pleura damage can be detected. Coughing becomes painful, breathing is difficult. When listening in the chest, wheezing is observed.
If the mammary gland is affected in cows, an increase in lymph nodes above the udder can be observed with the formation of dense and inactive tubercles. Milk is obtained in the form of a curd mass or with impurities of blood. In the case of generalized tuberculosis, an increase in tuberous lymph nodes located superficially is observed.
Pigs can hurt almost asymptomatically. In case of extensive lesions, vomiting, shortness of breath and coughing can be observed. In relatively rare cases of goats, sheep and horses, the symptoms are rarely pronounced. In the case of a severe clinical picture, the symptoms are similar to those described above.
Birds (ducks, geese and chickens, turkeys) suffer from chronic tuberculosis. In this case, obvious clinical signs, as a rule, are not observed. It is possible to determine the disease in chickens by their immobility and thinness. The crests and catkins in birds take a pale color and shrink, the pectoral muscles atrophy. Most often, birds die as a result of exhaustion.
Few characteristic features can also be observed in cats, dogs and wild fur animals. Similarly to birds, exhaustion, coughing and difficulty in the respiratory process (with lung damage) are observed. Weakening leads to death.
Diagnostic Methods
Basically, a study is carried out on tuberculosis of animals of an allergic nature using an intradermal tuberculin test. The drug is injected into the middle of the neck region of cattle, pigs - near the outer surface of the ear, goats - in the lower eyelid, fur animals and dogs - in the thigh. The hair is cut off before the injection, the feathers of the birds are plucked. The skin is treated with ethyl alcohol.
After 72 hours, a reaction to tuberculin is evaluated. In unfavorable situations, repeated administration of the same dose is permissible. When the skin is thickened, the thickness of the fold is measured in millimeters and compared with the unchanged area.
If certain normative figures of such a thickening are exceeded (from 3 mm or more), the animal is considered to be responsive to tuberculin. In this case, the general immunoreactivity of the body should be considered. A weak reaction may be in individuals of low fatness, old and weakened.
A small number of animals with the most striking signs are slaughtered. Part of the tissue sent for bacteriological research in the veterinary laboratory. You should be aware that in the event of a positive diagnosis, phagocytosis is incomplete. The immunity formed in this case does not serve as a measure of further protection.
As in humans, BCG vaccine prophylaxis is possible in animals. However, in most countries this practice is not accepted.
Animal tuberculosis prevention
Is any early action possible? They are regulated by the current sanitary and veterinary rules for animal tuberculosis. Farms related to the prosperous are equipped with healthy individuals with the acquisition of the same feed. All incoming livestock are quarantined with a tuberculosis test. Food waste is processed thermally. Serve animals of people with tuberculosis are not allowed. Premises for livestock are periodically disinfected, mites and rodents are destroyed in them. The quality of feeding and other conditions of detention are monitored.
In order to prevent animal tuberculosis, a planned annual study of livestock for this disease is provided. Cows and bulls are inspected twice a year - before the spring pasture in the pasture and in the fall, at the time of setting up for winter maintenance. Young growth is checked from two months of age annually. Other animals - depending on the danger of the epidemic. At the same time, it is supposed to examine animals belonging to private owners.
Is treatment possible?
Treatment of diseased farm animals is not performed. They are usually taken for slaughter. If the presence of the disease is established in the village (on the farm, in the herd), any animal that responds to tuberculin is considered sick. Within two weeks, it must be sent for recycling.
If we are talking about a prosperous economy, individuals reacting to tuberculin undergo additional studies by ophthalmoprobe or an intravenous test for tuberculin. In the case of a positive reaction, a control slaughter is carried out with a study of the material obtained in a veterinary laboratory. Having discovered as a result of a bacteriological test the fact of the defeat of animals by tuberculosis, the whole economy is declared unsuccessful for it with all the relevant restrictions, as well as with the preparation of a plan of measures for recovery.
According to the scale of the spread of the disease, a different degree of trouble is classified. Limited is one when the number of sick animals detected using a double test for tuberculin is no more than 15% of the total population. If this figure is exceeded, the degree of trouble is considered significant.
Farm Livestock Improvement
How is cattle herd recognized as dysfunctional being rehabilitated? The methods of this are as follows: isolation of sick animals or their groups with subsequent destruction or a lump-sum replacement of the whole livestock with a healthy herd. In both cases, a whole range of veterinary and sanitary measures is mandatory. According to the instructions, the premises freed from sick cattle are disinfected with sanitary repairs. Pastures on which sick animals were grazed are used only after 2-4 months in various regions of the country.
Restrictions from dysfunctional farms can be removed only after the complete completion of all sanitary measures with final disinfection and mandatory laboratory quality control of the latter.
If the disease is limited, heal the herd through systematic research, selection and slaughter of diseased individuals. Tuberculin tests are done intradermally for all cattle from the age of 2 months with a regularity of 45-60 days. Other animals, including dogs and cats, are also being tested for tuberculosis. Individuals who have responded to tuberculin are considered ill. They are subjected to isolation and surrender within 15 days for slaughter.
If tuberculosis is established in the poultry farm, all poultry belonging to the dysfunctional workshop (poultry house) is subject to surrender for slaughter, followed by veterinary and sanitary measures. After the restrictions are removed, a new herd is formed from healthy young animals. Eggs obtained from the birds of the workshop or poultry house, recognized as dysfunctional, are not allowed for incubation or use in the confectionery industry and in baking bread.