Tuberculosis in cattle: prevention, diagnosis and treatment

Tuberculinization of cattle is a veterinary measure aimed at identifying animals with tuberculosis. It should be done twice a year. Tuberculinization is carried out using a special preparation – purified tuberculin, which causes an allergic reaction in cattle, which makes it possible to determine the degree of pathology. Tuberculin is injected subcutaneously, and if tuberculosis is suspected, an additional set of studies of cattle is carried out.

What is bovine tuberculosis

Koch’s wand

Bovine tuberculosis is an infectious disease that occurs in a chronic form, characterized by the formation of certain nodules – tubercles in the affected organ. The disease is diverse in its course, manifestation, and can affect different organs. Bovine tuberculosis is common in many countries, the degree of danger of the disease continues to increase: at the beginning of the XNUMXst century, the situation in the world with respect to tuberculosis has worsened. The disease causes damage to large and small farms due to a significant decrease in animal productivity, early culling, high costs for therapeutic measures and preventive measures.

Despite the fact that tuberculosis has been known for a long time, it was described by Hippocrates, effective measures to combat the disease have not yet been found.

Many species of domestic and wild animals, birds and humans are susceptible to tuberculosis. The disease is characterized by mass character, which depends on many reasons – reduced functions of the immune system, the presence of chronic pathologies in cattle, unbalanced feeding, lack of walking, high humidity in the barn and other provoking factors. That is why it is necessary to identify the infected individual in the herd as soon as possible.

The causative agent of tuberculosis in cattle

The causative agent of tuberculosis in cattle is Mycobacterium tuberculosis. It is considered an anaerobic bacterium that does not form spores. The forms of the pathogen are varied, resembling straight or slightly bent sticks. There are rounded shapes, in the form of a chain. There are practically no single organisms in the colony.

Tuberculosis in cattle has 3 types of pathogen that lead to infection: bovine, avian and human forms of the microorganism. However, they are able to disguise themselves and be reborn:

• the human strain infects cattle, pigs, fur-bearing animals, dogs and cats are less likely to be infected;
• bovine strain (paratuberculosis) infects cows, is transmitted to humans, as well as domestic and wild animals;
• the avian strain infects birds but occasionally occurs in pigs.

The main differences between these forms include different virulence for animal and human species.

The main ways of infection:

• airborne, in which the disease is quickly transmitted to other cattle, especially in cramped, poorly ventilated areas;
• alimentary (the pathogen enters the body of a healthy animal through the digestive system);
• contact, which is quite rare in cattle;
• intrauterine infection at calving.

The causative agent of tuberculosis is quite viable: in air-dried lungs, it remains active for 200 days, in soil, manure up to 3-4 years. The sun disinfects the bacterium after 2-3 days; in infected cattle corpses, the microorganism continues its harmful activity for about a year. Heating and boiling are detrimental to Koch’s wand. Chemical agents disinfect the bacterium no earlier than an hour later, depending on the activity of the substance.

Tuberculinization of livestock

Sources of infection are:

• air contaminated during coughing and sneezing;
• infected milk;
• saliva;
• urine and faeces of sick cattle;
• contact with infected wild animals.

Types of tuberculosis in cattle

There are pulmonary and intestinal forms of tuberculosis in cattle according to the location of the pathology. Less often, lesions of the serous integument, genitals, udder tuberculosis in cows or a generalized form of the disease are diagnosed.

However, the lungs are most often affected by tuberculosis in cattle. This form of the disease is characterized by a cough, a slight increase in body temperature, while the appetite and productivity of the animal are within the normal range.

As tuberculosis develops, signs of inflammation of the lungs and pleura appear. Cough becomes painful, breathing is rapid, accompanied by wheezing. Cough attacks are worse in the morning and at night, sputum is abundantly secreted. In the chest of cattle, wheezing is heard during percussion. A strong pain syndrome is experienced by a cow with inflammation of the lungs during palpation. In addition, there is a rapid depletion of the animal, the skin looks dry, the coat loses its luster, and the lymph nodes increase. This leads to a narrowing of the esophagus and subsequent disruption of the scar and digestion in general.

In case of tuberculous lesions of the mammary gland in cows, the supra-vaginal lymph nodes increase. The udder turns red, swells. During milking, watery milk with cottage cheese flakes is released, blood clots may be contained.

infected individual

With the defeat of the genitals in bulls, pathologies of the genital organs are noted, including orchitis (inflammation of the testicle), uveitis (inflammation of the choroid of the eyeball) is often observed. In cows, barrenness, fetid discharge from the genitals, increased hunting are noted.

Symptoms of tuberculosis in cattle

Usually, tuberculosis in cattle occurs in a chronic form, in calves, most often in an acute form. Most infected animals do not differ from healthy individuals in general condition, behavior, appearance. The appearance of symptoms, pronounced forms of the disease indicates a long-standing infection.

In the development of tuberculosis in cattle, several stages of the disease are noted:

1. Primary tuberculosis. It has several forms – from the initial complex and the period of early generalization.
2. Secondary pathology. Has a period of late generalization or tuberculosis of a specific organ.

Primary tuberculosis is the stage of the disease that occurs after infection and is manifested by the primary complex.

The primary complex, which is localized in several systems of the cattle body at once, is called complex. Early generalization of the disease – its spread throughout the body. Secondary tuberculosis develops as a continuation of the primary one or occurs as a result of re-infection (reinfection).

Distinguish between an open (active) form of tuberculosis in cattle and a closed (latent) form of the disease. With open tuberculosis, the pathogen is released into the environment with feces, urine, milk, sputum. Tuberculosis of the intestines, uterus, breast is always considered an open form. The closed form of the disease is characterized by the presence of foci without the release of the pathogen into the external environment.

Tuberculosis of cattle in the photo

Despite the fact that the disease occurs more often in a latent form, the owner of the animal should be alerted by the following signs of tuberculosis in cattle:

• dyspnea;
• increased body temperature;
• sharp depletion of the animal;
• loss of appetite;
• decrease in productivity;
• dry skin;
• cough, sputum production;
• nasal mucus, increased salivation;
• enlargement of the pharyngeal glands;
• disruption of the digestive system.

With generalized tuberculosis, an increase in lymph nodes throughout the body of cattle is noted.

Diagnosis of tuberculosis in cattle

Diagnostic measures should include clinical, laboratory, pathoanatomical methods, as well as an allergic intradermal tuberculin test. It is necessary to exclude diseases with similar symptoms: pericarditis, contagious pleuropneumonia, pasteurellosis, pseudotuberculosis, helminthic invasions.

The main and most reliable method for diagnosing tuberculosis in cattle, other animal species and humans is an allergy test. To do this, use the classic version of tuberculin, which contains dead cultures of tubercle bacillus. The drug can be administered to cattle subcutaneously or by instillation into the eyes. Tuberculinization should be carried out 2 times a year before the animals are taken out to pasture in the spring and before the transition to winter keeping. As for the young, each calf is tested at two months of age. After the introduction of the drug, it is necessary to monitor the reaction to tuberculin in cattle after 72 hours. It is counted if in cows the skin fold differs in thickness by more than 3 mm, in bulls – in the presence of edema. In addition, you need to track the reaction of the skin (swelling, redness, temperature). Sometimes, in order to clarify the diagnosis of tuberculosis, to identify a nonspecific reaction of the body, cattle are subjected to differential diagnosis using a simultaneous test.

Diagnosis in calves

Also important is the clinical method for diagnosing cattle, in which the veterinarian pays attention to the clinical symptoms of the disease.

Treatment of tuberculosis in cattle

Veterinary medicine does not have an effective treatment against bovine tuberculosis. Thus, it is impossible to cure infected animals. But according to the results of a study of the entire livestock, this farm is classified as unfavorable, and a number of recreational activities are carried out in the herd.

Some restrictions are imposed on the herd, taken under control by the decision of the district administration, which will prevent the spread of infection. Also, a specialist is assigned to the farm, who will monitor the strict implementation of the instructions for combating tuberculosis in the herd of cattle.

Improving activities in the farm are carried out in the following ways:

1. Regular laboratory tests to identify all infected cattle. Checks are carried out with an interval of 60 days. If infected cows are found, they should be culled immediately. Tests are carried out until all animals in the herd show a negative result. Only in this case, quarantine for bovine tuberculosis is removed from the livestock, and the farm will be considered healthy.
2. Complete replacement of the herd of cattle with healthy animals with mandatory disinfection of the barn and surrounding areas. This method is effective if the percentage of positive cows is too high (more than 15% of the total number of heads in the herd). Then the farm is quarantined.

Livestock health measures

Full herd replacement activities include the following:

• all animals, including young animals, are sent for slaughter;
• milk obtained from all cows is boiled for about 5 minutes at a temperature of 90 ° C before disposal;
• the cowshed is cleaned of dirt, manure, the old coating is removed;
• the entire area is treated with a solution of caustic salt and formaldehyde;
• garbage is taken out of the farm, as well as manure, topsoil;
• All equipment must be recycled.

After all the work, the barn is restored, the rest of the premises, the adjacent territory, drinkers and feeders are mounted. Then everything is re-treated with disinfectant solutions, after which samples are taken for the presence of the pathogen. After receiving negative results, quarantine is removed, the owner can purchase a new herd of cattle from those farms that are listed as safe in the veterinary service. The new flock is also sampled with tuberculin.

tubercles

Pathological and anatomical changes in tuberculosis in cattle

At autopsy of a cow infected with tuberculosis, the following changes are noted:

• some nodules (tubercles) in organs and tissues ranging in size from a few mm to 10 cm, which have a gray color of a dense structure;
• changes in the serous integument in the abdominal cavity;
• tubercles and ulcers of the mucous membranes;
• suppuration, cavities;
• violation of gas exchange in the lungs;
• lung necrosis with purulent formations;
• severe exhaustion;
• signs of bronchopneumonia;
• inflammatory processes in the lymph nodes;
• pathological changes in the liver, kidneys, heart, bone marrow.

The main symptom of tuberculosis at autopsy of an animal is the presence of tubercles, which can be located in different areas of the lesion. When the nodule is excised, a layered structure of a cheesy appearance is visible.

Prevention of tuberculosis in cattle

Quarantine on the farm

The instructions for combating bovine tuberculosis provide for the implementation of certain sanitary and veterinary standards. Cattle owners need:

• register individuals with the veterinary service, the tag with the number should be kept throughout the life of the animal;
• movement of individuals, purchase and sale to be carried out with the permission of the veterinary authorities;
• carefully prepare feed, excluding its infection;
• keep all new animals in quarantine for a month;
• at the slightest suspicion of tuberculosis, notify veterinary specialists;
• timely carry out vaccination and examination of cattle for this disease;
• comply with all norms of feeding, keeping and caring for livestock;
• take measures to combat rodents;
• enrich the diet of cattle with vitamins and microelements;
• identify and discard infected individuals in a timely manner;
• check meat at the slaughterhouse;
• monitor the health status of the farm staff;
• introduce quarantine if necessary, follow all the rules in accordance with the instructions.

In addition to these measures, the BCG vaccine is used to develop immunity and as a specific prophylaxis. It is administered to animals with an interval of 14 days. Such strict measures are necessary, since bovine tuberculosis is not treated, often occurs in a latent form and causes enormous economic damage to farms. Therefore, preventive measures, diagnosis of the disease are extremely important.

Can tuberculosis be transmitted to humans from cattle?

Tuberculosis is a highly contagious disease, and the bovine strain is also dangerous to humans. There are several ways of transmitting the pathogen from a sick individual of cattle to a person:

1. Airborne. A person can become infected, especially with an open form of tuberculosis, when the animal releases microparticles of mucus and bacteria into the environment. If the temperature in the barn is high, it is humid, there is no ventilation, then Koch’s stick is able to stay in the air for a long time and be viable.
2. Meat and dairy products. With bovine tuberculosis, meat and milk contain a huge number of pathogens. By consuming products without prior heat treatment, a person may become infected.
3. Contact. When suffering from tuberculosis, the animal releases feces, urine, and sputum into the environment. Thus, livestock litter becomes infected. Workers, having damage to the skin, can become infected when cleaning the barn.

Milk should be boiled

Also, infection can occur from birds, but the disease will proceed in a different way.

Is it possible to drink milk if a cow has tuberculosis

The milk of infected cows is extremely dangerous for humans, especially for children. Infection is possible by 90-100%. Koch’s stick is acid resistant. Therefore, even in sour milk, it remains viable for 20 days, in cheeses and butter up to 1 year, in frozen foods up to 6-7 years.

Milk from healthy cows, but obtained from an unfavorable farm, is treated at a temperature of 90 ° C for 5 minutes. Contaminated milk is strictly forbidden to eat. However, after heat treatment, it is permissible to use it for fattening animals on the farm.

Milk from sick animals differs in composition. In it, the amount of albumin, globulin increases by 2 times, fat content decreases, viscosity increases. Cheeses will not be obtained from such milk, yogurt will be watery, kefir will be heterogeneous.

The quality of meat and dairy products is monitored by a veterinary and sanitary examination, which passes products of good quality for sale. In the presence of generalized tuberculosis, all carcasses, by order of the VSE, are disposed of, including bones and internal organs. Carcasses with a tuberculous focus in any one organ or lymph node are sent for processing into sausages or canned food, in compliance with all veterinary standards. Bovine organs affected by tuberculosis are sent for disposal.

Conclusion

Tuberculinization of cattle is one of the main measures for the timely detection of infected individuals in farms. The event is held within the framework of the state task, it has clear instructions approved by the Deputy Head of the Rosselkhoznadzor. Such strict measures are necessary, since the situation of bovine tuberculosis in our country causes some concern among veterinary specialists. The adopted system of improvement of farms has significantly reduced the number of infected animals, but did not bring the desired result. Therefore, farm owners are required to be attentive to this problem and comply with all sanitary rules.