Bovine leukemia: causative agent and symptoms, how it is transmitted and danger to humans

Infectious diseases are common in dairy farming. Infectious agents can affect various organs, even the blood. Leukemia of a viral nature is a serious disease that can affect representatives of all breeds. Consider the causes, stages and symptoms of bovine leukemia, diagnostic and therapeutic measures, is there a danger of the disease to humans.

Causes and how is the virus transmitted?

The causative agent of leukemia in cattle - bovine leukemia virus (BLV), of the Retroviridae family, is morphologically similar to the virus that causes leukemia in other animal species.The virus is able to remain in the cell for a long time in a bound state with the genome, without showing activity. It is activated when the metabolic processes and the body's immunological defenses deteriorate.

Leukemia (hemoblastosis, leukemia) is a tumoral blood disease that can be asymptomatic. It is manifested by the proliferation of cells of hematopoietic and lymph-forming organs, which then infiltrate into other organs, where tumors appear. They can form in the lymph nodes, spleen, heart, kidneys, abomasum, kidneys.

The virus is transmitted to cattle, buffalo, zebu and sheep. The causative agent lives in the external environment for a short time, loses its infectious properties in 3-6 hours, and dies when it is exposed to common disinfectants. In fresh milk, the virus persists for 18 days; when pasteurized, it dies in a few seconds.

He althy animals become infected through blood and saliva during mating. Calves - through colostrum and milk, 10-20% are born already infected.It is believed that the virus is carried by blood-sucking insects. Infection is facilitated by crowded content, herd grazing on common grazing, feeding calves with the milk of sick cows, and the use of sick bulls for mating. Bovine leukemia is now seen as a disease that poses a threat to the gene pool of breeds and reduces the number of productive livestock.

Stages and symptoms

The course of the disease is divided into several stages, which are characterized by certain disorders and symptoms. Pathogenesis is determined by the interaction of the virus and the cell. Leukemia is characterized by a predominantly latent form.

The disease begins with the activation of the pathogen, various unfavorable external or internal factors can become activators.

Hatchery

It can take 2 or more weeks from infection to the first signs.The early stage of the disease is asymptomatic, the productivity and reproductive function of cows remain at the same level. At this time, the sick animal is already spreading the virus. A cow, despite the presence of a pathogen in the body, may never get sick with leukemia, the pathogens will remain in the body in a passive state, but will be transmitted to other animals with the patient's secretions.

Hematological

At this stage, pathological changes begin to appear in the blood of infected animals, which flows through the vessels, and not just in the blood-forming organs. In leukemic individuals, the condition worsens, they quickly get tired, poorly digest food, reduce milk yield, lose weight.

Digestive disorders, weakening of the heart, icterus or cyanosis of the mucous membranes are not uncommon.

Breathing becomes heavy, dewlap, belly, udder swell in animals, urine output is disturbed. Superficial lymph nodes on the jaw, udder, near the ears, above the knees increase. They are dense or slightly elastic, mobile and do not hurt.

Tumor

This stage is manifested by the emaciation of cows, their lymph nodes increase, their eyes protrude. Such individuals of cattle often get sick, often remain barren, there may be abortions, and the number of calves born is reduced. Cow productivity drops.

Young cows show tumors in the lower neck, thymus and skin. Due to the decrease in leukocytes and the appearance of pathological forms of cells in the peripheral blood, the immune system is quickly depleted, and the calves die. In calves, the disease is acute and can die within a few weeks of symptom onset.

Diagnostic measures

In the early stages of the disease, leukemia in cattle is detected by enzyme immunoassay and polymer chain reaction. The diagnosis is made according to epizootological, virological, histological, hematological studies, as well as taking into account clinical signs.In a hematological study, the number of leukocytes, young cells and the number of lymphocytes are determined as a percentage. Auxiliary diagnostic methods - biopsy of lymph nodes, liver and spleen.

Leukemia is differentiated from tuberculosis, actinomycosis, traumatic pericarditis, hepatitis, mastitis, reticulitis, brucellosis and paratuberculosis.

What to do if a cow has leukemia?

The disease is chronic and severe, which causes significant damage to the body of the animal, so it is not treated. The virus can be integrated into the genes of the cell, and drugs have not yet been developed with which you can remove it from there. There is no official therapy for the treatment of leukemia in cows, and there are no traditional methods.

When diseased individuals are identified, they are separated from the herd and reared separately or immediately slaughtered. If there are more than 10% of such individuals, they are slaughtered, the rest are examined every 3 months. If there are many cases, the animals are handed over for slaughter and replaced with new ones.

Possible complications and consequences for the animal

Cows with leukemia will die because there is no cure. When this happens depends on the state of he alth of the animal, on how long it can resist the disease. Carriers, if they do not get sick, can live for many years, and the unactivated virus will not affect he alth and productivity. Breeding carriers of the leukemia virus is not recommended.

Prevention

When buying new animals in the herd, you need to conduct a study of their blood, try to choose individuals from farms that are safe for the disease. If the analysis establishes that they are he althy, they can be introduced into the herd, infected - sent for fattening. These cows should be kept separate from the rest, fed with immunostimulating supplements.

Caves born from leukemia cows also need to be tested for the presence of the virus.Equipment and milking machines, if possible, should be used individually or at least disinfected before milking he althy animals. If there is no he althy bull in the herd, artificial insemination can be used. The room where the cows stood should be cleaned and disinfected with a 2-3% solution of caustic soda.

Is there a danger to humans?

The virus from cows is not transmitted to humans, and the disease does not develop. Therefore, you can work with animals without fear of infection. But there are sanitary requirements for milk and meat.

You can drink milk, but only after 5 minutes of boiling or pasteurization. When a certain temperature is reached, 2 tens of seconds is enough for the viruses in milk to die. Milk can also be disinfected under ultraviolet radiation. However, the quality of milk remains low. From it you can not cook yogurt, cheese, dry. It has more than usual protein and less solids. It contains toxins produced by the virus.

Meat is unfit for consumption if internal organs and muscles are affected. If the muscles are not affected by tumors, it is boiled before use or sent for processing into meat products.

Leukemia in cattle is an incurable disease, animals can get sick in any farm. The main way to prevent the spread of disease in the herd is preventive measures. If a cow becomes infected and the disease begins to develop, she is doomed. After a while, the animal will die. All that can be done is to put him on intensive fattening or to score right away.

Economic damage from bovine leukemia is determined by the loss of funds due to forced slaughter of livestock, death of animals, reduction of milk and meat productivity.The volume of young animals sold is also decreasing. Today, leukemia is considered a disease that threatens the breeding gene pool of cattle breeds.

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