Leukemia in cows is characterized by infection of RNA with an oncological virus. Malignant lesions affect the hematopoietic system, spreading to other internal organs. The disease belongs to the group of the incurable.
Causes of occurrence and how is the virus transmitted?
The leukemia virus carrier is an altered ribonucleic acid macromolecule of the animal itself. After penetration into the body of cattle (cattle), it changes the structure of the cells of the circulatory system, thereby violating its functionality. Against this background, an excessive amount of lymphocytes is produced, tissues grow and tumors form.
The latent incubation period is quite large - up to 7 years. This period can be completely asymptomatic. In this case, the cow is a virus carrier. Therefore, it can infect other individuals.
Ways of transmission of the virus:
- direct contact with a sick animal;
- through working utensils and tools;
- by semen from an infected bull;
- through blood and saliva;
- the virus is carried by blood-sucking insects - mosquitoes, bugs, etc .;
- through milk, colostrum, amniotic fluid, placenta.
Influencing factors :
- low immunity when the owners give poor-quality food, contain cattle in inappropriate conditions;
- crowded content;
- stress (when animals are beaten);
- the presence of any pathologies and the lack of adequate treatment;
- genetic impact.
The virus is transmitted in various ways, it is not affected by climatic conditions, time of year and external factors. However, the microorganism is vulnerable to heating up to 60 degrees and treatment with chlorine, sodium hydroxide (3%).
Learn more about cow leukemia and how to transmit the virus from this video:
Stages of the disease
Forms of the disease:
- An enzootic species is found mainly in adult cattle, and lasts a long time.
- The sporadic type affects young animals up to 3 years of age. It is rare.
Stages of Cow Leukemia:
- Stage No. 1 - incubation (hidden) is characterized by the moment of infection penetration into the animal organism. The duration is different - the stronger the cow's immune system, the longer the latent degree lasts. Symptoms are absent.
- Stage No. 2 - hematological. The blood fluid of cattle changes its structure, the concentration of leukocytes increases, and against this background, bleeding develops. Symptoms occur only on the part of the gastrointestinal tract. You can detect the disease based on the collected tests.
- Stage No. 3 - tumor. In the organs of hematopoiesis, neoplasms grow. This degree appears after 5 years from the moment of infection.
The causative agents of leukemia are primarily found in milk, so farmers are required to regularly bring fluid samples to a microbiological laboratory for research. It must be remembered that the infection is transmitted instantly.
Symptoms begin to manifest from the 2nd stage, as the pathology progresses, the signs intensify and complement. Leukemia can be determined by the following symptoms:
- The cow develops constant diarrhea, which can change dramatically with constipation. In this case, blood clots can be detected in feces.
- Lymph nodes increase, up to the size of the ball. Eyeballs also increase - they bulge out (develops eye-eyes).
- The animal becomes susceptible to any disease. The slightest hypothermia leads to his cold.
- The cow becomes barren. If a pregnant female is fertilized, then she has miscarriages.
- Infected calves are constantly sick - they have difficulty breathing, digestive problems are detected.
- Cattle are rapidly losing weight, quickly getting tired. Exhaustion occurs.
- The cow becomes weakened, her breathing quickens.
- If we consider the udder, then it becomes noticeable skew in the size of the shares. The chest, abdomen and udder swell .
- The quality of milk is getting worse, and the amount is significantly reduced.
- The animal begins to limp on its hind limbs.
- Visible neoplasms form on the body.
Possible complications and consequences for the animal
There is an opinion among veterinarians and farmers that leukemia definitely leads to the death of an animal. Yes, this is because until today no effective vaccines have been developed, although studies have been conducted repeatedly over many decades. Therefore, when an individual is infected, the farm owner must take care of the rest of the livestock.
Is there a danger to humans?
As it became clear, leukemia in a cow is dangerous for all cattle. And how does pathology affect the human body? After all, we consume meat and milk. As it turned out, after numerous tests, the human body is not susceptible to strains of cow leukemia. In world practice, no cases of infection have been identified.
However, doctors recommend caution about livestock products. The fact is that these viruses easily adapt to all conditions, they are flexible and mutating. And this does not give any guarantee that at any moment a new, unknown to humans strain of VLCRS, which is a danger to human life and health, cannot appear.
Drinking raw thermally processed milk and eating meat from an infected animal is contraindicated. The reason is that oncological viruses, being in the body of a cow, accumulate toxic and other harmful substances. Therefore, a person can get a disease of a toxic nature.
It is known that the pathogen dies during heat treatment, so infected foods must be boiled. But on the other hand, toxins cannot be destroyed by heat. Therefore, such meat and milk is categorically undesirable to eat.
To make a diagnosis, it is necessary to take blood from an animal, since the virus initially affects the circulatory system. Therefore, it is localized in the same place. Lesions are leukoblastic cells. The study is based on such techniques:
- RID - immunodiffusion reaction. Blood is collected 2 weeks after collection of tests for tubercle bacillus. If the cow is pregnant, then the collection of biological fluid is carried out 1 month before calving or 30 days after delivery. Examined in this way you need all the animals that have reached six months.
- Hematological analysis evaluates the concentration of lymphocytes in the blood fluid for 36 hours. If during the examination period it is not possible to obtain an accurate result, the analysis is repeated after a month. As a rule, the number of this substance becomes lower, but with further investigation it again increases.
If the result is positive and is observed twice by both methods, the animal is destroyed. If the plus is noted only by hematological analysis, then the cow can be considered healthy. Additionally, histological, serological and virological analysis can be performed.
Leukemia cannot be cured. The reason is that the pathogen infects lymphocyte cells. To destroy the virus, one would have to neutralize the lymphocytes, and this is fraught with immunodeficiency. Simply put, a condition develops, as in HIV and AIDS.
If 2 or more infected cows are found on the farm, the farm is classified as unsuccessful for leukemia. Based on this, prescribe restrictions and develop a plan for the improvement of livestock.
- Separation of infected cattle from healthy individuals. Sick animals cannot be kept together with the rest of the livestock, they must be disposed of.
- Even if the animal is at the initial stage of leukemia, it is strictly forbidden to collect milk and eat milk. The same applies to meat after slaughtering cattle.
- You can not transport cattle to another locality and move even within the limits of this settlement. To do this, you must obtain permission from the veterinary service.
Improvement of livestock can be carried out by various methods. It depends on the degree of infection of the herd. All methods are aimed at the study of the entire livestock, slaughter of infected individuals and partial replacement of animals. Farmers must strictly comply with the requirements for the prevention and control of this disease, adhere to veterinary and sanitary rules during zootechnical and veterinary measures.
Initially, it is necessary to carry out blood sampling from each animal. If leukemia is confirmed, the infected cattle are immediately transferred to another place, after which they are sent for slaughter. The remaining cows are subjected to ongoing research. If the disease is not detected within six months, the farm gains leukemia-free status.
Since the farmer, after culling sick animals, loses most of the cows, he needs to replenish the herd. To do this, purchases are made from other farms. It is important to observe the quarantine mode.
Preventive measures are included in the list of mandatory actions for the maintenance of cattle. This helps prevent infection and the further spread of leukemia:
- Cattle need to be acquired only in those households where the incidence of leukemia is not in the pedigree. Bulls and cows must be completely healthy.
- Be sure to observe quarantine. For this, a new supply of livestock is placed in a separate room for 2 months. During this period, the cows are examined by a veterinarian, they are examined, at least 2 times. If the result is negative, livestock are introduced into the general herd. If positive, send for fattening.
- Reed-positive individuals are kept in a separate room, they are intended for fattening.
- If the calf was born from a sick cow, it is checked several times for leukemia, as young animals are not always infected from the mother.
- It is advisable to keep cows with weakened immunity separately, as there is a risk of infection. The farmer should feed them with special additives to strengthen the immune system.
- Milking machines, veterinary treatment and other manipulations always start with completely healthy cows.
- Calves are numbered using liquid nitrogen, disinfected tools thermally and chemically.
- The insemination bulls need to collect blood four times a year.
- Pregnant cows are examined 30-60 days before the expected calving.
- Sanitary herd conditions must meet standard requirements. All tools, devices and equipment must be properly disinfected.
- Free mating of bulls and cows is excluded.
- If there is no insemination on the farm, sperm is purchased, which is sent for laboratory testing before insemination.
Cows leukemia is a dangerous disease that quickly spreads from a sick animal to a healthy one. Therefore, prevention is considered the most important part of farm maintenance. Leukemia can affect not only cows, but also goats, sheep and other domestic animals. Take care of cattle health from birth.