Leukemia in cows: what is it, measures, prevention

Viral bovine leukemia is widespread not only in Our Country, but also in Europe, Great Britain, and South Africa. Leukemia is causing irreparable damage to the cattle industries. This is due to increased culling of the herd, waste disposal, treatment, and other activities. More intensive development of the disease occurs in the dairy industry.

What is leukemia in cattle

The causative agent of the disease is an infectious pathology containing an oncogenic virus. It is similar to leukemia in other animal breeds. There is another option to which sheep and goats are tolerant. Leukemia is associated with malignant proliferation of hematopoietic tissue cells and has a tumor nature. The virus can be latent for a long time and not manifest itself. Rapid development begins with a decrease in immunity. In the course of the disease, the immune system is completely destroyed, so the animal is prone to re-infection with leukemia even after treatment. Lack of immunity leads to an increase in the duration of other diseases.

The causative agent of leukemia in cattle

The causative agent is a specific leukemia virus. It is extremely unstable in the external environment and dies at 76 degrees in 16 seconds. Boiling water kills him instantly. Destroyed by various disinfecting compounds:

• 2-3% sodium hydroxide solution;
• 3% formaldehyde;
• 2% chlorine solution.

It also deactivates under UV light in 30 minutes. In direct sunlight – 4 hours. Sensitive to various kinds of solvents – acetone, ether, chloroform.

The bovine leukemia virus has a spherical structure, up to 90 nm in size. Consists of a cubic core surrounded by a lipoprotein shell. Contains a genome with two helical RNA molecules.

Antigenically, bovine leukemia viruses are related to, but distinct from, retroviruses. Based on similarities and differences, it can be assigned to a special group – type E.

How is bovine leukemia transmitted?

The main reason for the pathogenesis of bovine leukemia is neglect of livestock, lack of disinfection of premises, and ignoring preventive measures.

Unsanitary conditions in the barn

Transmitted:

1. With direct contact between animals through biological fluids – blood, milk, semen. Calves are already born infected or acquire the disease through mother’s milk. In the herd, they can become infected even in the absence of an inseminator bull. Animals jump on each other, damaging the skin. If one animal is infected, it can transmit the virus through lesions.
2. Through the bites of blood-sucking insects. Anyone that feeds on blood is dangerous. Methods of struggle are not found.
3. Through non-sterile veterinary instruments during mass examinations, vaccinations. Symptoms of the disease do not appear immediately. During this time, most of the herd may be infected.

There are 2 forms of leukemia – sporadic and enzootic. The first is very rare and develops only in young animals. The second has a latent period of more than 3 months. Affects adults.

Symptoms of leukemia in cattle

The initial stages of the disease are asymptomatic. Only in the later stages are health disorders noted. After a change in the composition of the blood, the signs become more noticeable:

1. Weakness of the animal.
2. Increases respiration.
3. Weight loss.
4. Problems with the gastrointestinal tract.
5. Swelling of the breast, udder, abdomen.
6. Lameness in hind legs.
7. Enlargement of lymph nodes.
8. Noticeable tumors.
9. Puffy eyes. Rarely appears.

Exhaustion and weakness appear as a result of poor digestibility of useful elements from feed. Reduced milk supply.

Stages of bovine leukemia

Any cattle are susceptible to leukemia. There are 3 stages:

1. Incubation. The hidden period is up to 3 months. It starts from the moment of the virus attack. Outwardly, it does not appear at all. Cows with strong immunity may take longer.
2. Hematological. It is characterized by a change in the composition of the blood with a rapid increase in white blood cells – leukocytes. Leukemia is analyzed by composition. At this point, the first disturbances in the work of the gastrointestinal tract begin.
3. The development of a tumor in the hematopoietic organs. This can happen 4-7 years after infection.

Enlargement of the prescapular lymph node in bovine leukemia

Early stages of the disease can be detected in milk tests. Therefore, it is extremely important to take it to the laboratory periodically. This will help isolate infected individuals and avoid mortality.

Methods for diagnosing bovine leukemia

The first case of leukemia with white blood cells in an enlarged spleen was described in 1858. Since the end of the 100th century, for almost 1969 years, scientists have been trying to find the causative agent of the bovine leukemia virus. Only in XNUMX it was opened. Leukemia came to our country with the importation of breeding stock.

Several diagnostic methods are known – primary, serological, differential. The primary method is used on farms. The basis for it is the pathoanatomical study of fallen animals, blood tests, the study of epizootological and serological data. A histological sample must be taken.

Signs of leukemia in the initial diagnosis:

1. Clinical.
2. Hematological changes – an increased number of leukocytes and atypical cells of the hematopoietic organs.
3. Pathological changes in the organs of the fallen cattle.
4. Positive result of histological studies.

With bovine leukemia, laboratory diagnosis is the most reliable way to determine the disease.

White blood cells are counted in a Goryaev chamber or under a microscope. Leukocytes and lymphocytes are compared with the data in the “leukemic key” table. Based on the number of bodies and blood morphology, a conclusion is made about the disease – a healthy animal, falls into a risk group or is already sick.

Serological studies highlight antibodies to the antigen of the bovine leukemia virus. Appear 2 months after infection of the patient – much earlier than noticeable hematological changes. Then they persist throughout life. The immunodiffusion reaction (RID) is the main research method in Our Country and other countries. Animals with positive RID results are considered infected. Such clinical results or blood tests immediately put cattle in the category of diseased.

The differential diagnosis of bovine leukemia defines the disease based on a range of chronic infectious and non-infectious diseases.

Diagnosis of bovine leukemia

These are tuberculosis, actinomyosis, brucellosis, hepatitis, cirrhosis, nephritis and other diseases of the liver, lungs, and bones. These diseases are accompanied by leukemia-like changes – leukemoid reactions.

Treatment of leukemia in cattle

To date, no effective treatment option has been found. Attempts have been made to eliminate bovine leukemia with a vaccine, but they have been unsuccessful. The main therapy is associated with the culling of cows and their slaughter. It is recommended to slaughter an animal at an early stage of the disease, so as not to torment and not lose profit on treatment. Milk from leukemic cows is prohibited by law. The same ban was imposed on the consumption of meat from diseased animals. Milk from virus carriers is subject to mandatory pasteurization. Then they are disinfected and used without restrictions.

According to the veterinary rules, in case of bovine leukemia, farms engaged in dairy farming are forced to slaughter the livestock completely. Treatment takes a long time and can take years.

Farms with a small number of cases – up to 10% of the livestock, separate leukemia cows and hand them over for slaughter. Serological studies are carried out every 2 months.

When the number of cases is more than 30%, not only serological studies are carried out, but also hematological studies after 6 months. Cattle are divided into groups that successfully passed the study and virus carriers. The sick are separated for slaughter.

Instructions for the prevention of leukemia in cattle

Farms with this disease are put under control and declared unfavorable. According to the rules for the fight against bovine leukemia, a number of restrictions are imposed on them to reduce the spread of infection. Quarantine measures do not allow:

1. Driving livestock inside settlements without the permission of a veterinarian.
2. Free mating of cows with sires.
3. The use of contaminated tools in the treatment of animals and premises.
4. Joint maintenance of healthy and sick.
5. Free import and export of animals.

Activities for bovine leukemia involve quarantine exposure of the entire newly arrived livestock. The sale of meat and dairy products is carried out only with the permission of the veterinary station.

During the quarantine period, regular disinfection of premises for keeping livestock and animal care items is carried out.

Disinfection of premises for leukemia

All waste products of cattle are disposed of.

To restore the livestock, replacement young animals are grown. It is kept in other premises, grazed on separate pastures. Upon reaching the age of 6 months, serological studies are carried out, then they are repeated every six months. According to the instructions for cattle leukemia, infected young animals are separated and fattened away from healthy ones. Then they score.

Pathological and anatomical changes in leukemia in cattle

An autopsy of dead animals is carried out periodically to study the course of the disease, the causes of death, the impact on individual organs and systems as a whole. Bovine leukemia leads to the elimination of the diseased livestock. An autopsy shows at different stages of the development of leukemia diffuse or focal infiltration into different parts of the body:

• hematopoietic organs;
• serous covers;
• digestive system;
• a heart;
• lungs;
• the uterus

The main forms of the disease are leukemia and reticulosis. Changes in leukemia:

• greatly enlarged spleen – up to 1 m;
• an increase in follicles;
• rupture of capsules with hemorrhage in the peritoneum;
• an increase in the supraventral lymph nodes in the tumor stage up to 10 * 20 cm;
• the smooth capsule is easily removed, the pattern of the tissue of the lymph nodes is smoothed;
• the liver, heart, kidneys sprout as diffuse or focal neoplasms from gray-white to gray-pink;
• pathology of other organs manifests itself at later stages of the disease.

Changes in reticulosis:

• uneven enlargement of lymph nodes;
• the capsule is not smooth, but rough;
• fusion of the capsule with adjacent organs and tissues;
• tumors of various sizes – from a pea to 30 kg;
• the color of the tumor is gray-white;
• a dense tumor is covered with foci of necrosis and hemorrhage;
• in the liver, spleen, endocrine glands, brain, dystrophic changes are noticeable;
• possible metastases in the abomasum, heart, other organs.

Conclusion

Bacteria that cause bovine leukemia cannot tolerate heat treatment. But the infection in the early stages is asymptomatic. If diagnostics are carried out in time, young animals, infected animals are isolated, antiseptic treatment is carried out, and sick ones are slaughtered, the likelihood of farms recovering from bovine leukemia will be higher. It is better to stop infected cattle in time than to completely lose the livestock.