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The secret you have to know about brucellosis in dairy cows

Posted on: July 25, 2019, by Eleanor

Brucellosis in dairy cows is a chronic zoonotic infectious disease caused by Brucella. Inflammation of reproductive organs, abortion of cows and infertility are the main characteristics of the disease, which not only affects the healthy development of the dairy industry but also poses a huge threat to human health. The Law of the People's Republic of China on the prevention and control of infectious diseases classifies brucellosis as a class B infectious disease. In recent years, with the rapid development of the dairy farming industry in various parts of the country, the incidence of brucellosis in cows has increased significantly in some areas. Next, let's understand the clinical and pathological changes of brucellosis in dairy cows and the comprehensive prevention and control methods.

The secret you have to know about brucellosis in dairy cows.
The secret you have to know about brucellosis in dairy cows.

Epidemiological situation

Brucella is a tiny globular polymorphic bacterium with slightly convex or straight edges, blunt rounded ends, negative Gram staining, no flagella, no spore formation, and virulent strains can have capsules. So far, seven species of Brucella have been identified. Brucella has a strong ability to live under natural conditions. It can survive for several months in the secretions, excreta, dry soil, fur, and dairy products of diseased animals. It is sensitive to light, heat and commonly used chemical disinfectants. The epidemic of the disease is seasonal and can occur in all seasons of the year, but it is more common in late spring and early summer. It has a wide range of susceptible animals.

At present, more than 60 kinds of livestock, poultry, and wild animals are known to be the host of Brucella and are highly infectious to sheep, cattle, horses, and pigs. The infection rate of dairy cows increases with sexual maturity, for example, calves are not susceptible to infection before reaching the mating age. Diseased animals and carriers are the main sources of infection. Vaginal secretions and milk after abortion contain a large number of Brucella. The disease is mainly transmitted through the digestive tract, but the cutaneous infection is also infectious. If the skin is traumatic, it is more likely to be invaded by pathogens. Other routes, such as conjunctiva, mating, and blood-sucking insects, can also be transmitted.

Clinical and pathological changes

The incubation period of the disease is 2 weeks to 6 months, with cow abortion as the main symptom. Abortion often occurs in 6 to 8 months after pregnancy. Several days before an abortion, it shows signs of childbirth, labia swelling, sagittal and rib subsidence, loss of appetite, vaginal discharge of gray or gray mucous secretion, abortion 2 to 3 days later, stillbirth or weak fetus. Weak fetuses often die from sepsis, and the placenta often stays after abortion, excluding brown-red lochia. After one week, the symptoms disappear and the pregnancy can be re-conceived.

However, abortion may occur in the future. If the abortion happens again, the second abortion will occur later than the first abortion. If the placenta is not discharged and develops into chronic endometritis, it may lead to long-term infertility in female cows, eventually losing feeding value, and some diseased cows may also have mastitis symptoms. Bulls often suffer from orchitis and epididymitis after infection, often accompanied by tenosynovitis, synovitis and other arthritis, and sometimes penis redness and swelling.

The pathological changes of the uterus and fetal membranes of pregnant cows are prominent. The membranes are yellow peptone-like infiltration. Some parts of the surface are covered with fibrin floccules and pus. Some or all of the villi are pale yellow, some are covered with gray and yellow-green fibrin floccules, and some are covered with fat-like exudates. There are pyogenic necrosis foci in bull testis and epididymis. Fetal subcutaneous hemorrhagic serous infiltration, lymph nodes, spleen enlargement in varying degrees, some scattered inflammatory necrosis, pale yellow or white mucus in the true stomach, gastrointestinal tract, bladder serosa point or linear hemorrhage.

Prevention and control measures

Cultivating healthy and stable dairy herds is not easy to introduce. If it is necessary to introduce cattle, we should know the basic situation of the introduced areas, whether brucellosis has occurred, and ensure the quality of imported cattle. After the introduction, the whole population should be observed in isolation for 2 months. After the isolation period expires, the results of two biological tests are negative, and then mixed breeding can be carried out. Scientific and reasonable feeding, giving full-price feed to meet the nutritional needs of dairy cows, can feed microbial preparations, can effectively improve the body's immune system function and enhance the resistance of cattle to disease.

At the same time, we should do a good job in environmental hygiene and epidemic prevention, disinfect the fetal clothes, secretions and contaminated mattress after delivery, bury them in deep and harmless way, disinfect the surroundings of contaminated pens, utensils and venues more than three times continuously, cut off the route of transmission, and avoid cross-infection. Regular quarantine surveillance should be persisted as an epidemic prevention system for a long time so that early prevention, early detection, and effective prevention and control measures can be taken at an early stage. In the process of monitoring and purifying, it is necessary not to miss detection and timely isolation and culling of cattle with positive brucellosis found in monitoring. Vaccination is an effective measure to control the disease.

At present, live vaccines are widely used in the world. For cattle of different periods, the vaccines and immunization methods of corresponding periods were selected for immunization. Brucellosis is a zoonosis. All veterinarians and breeders working in cattle farms are high-risk groups vulnerable to infection. Therefore, the strict operation should be carried out in vaccination or treatment of diseased cattle, a strict protection system must be observed, and good disinfection work should be done to avoid infection.

The secret you have to know about brucellosis in dairy cows.
The secret you have to know about brucellosis in dairy cows.

NO.1 Pathogens and epidemiological characteristics

Brucella is a group of small, immobile, spore-free, gram-negative, spherical or short-rod-shaped bacteria. Brucellosis is most commonly found in cattle and sheep and can be transmitted to humans. Brucella is divided into bovine, sheep and pig types. Brucella species are pathogenic to domestic animals and humans. Among them, Brucella Ovis has the highest pathogenicity and the greatest harm to humans.

Brucella is sensitive to heat, various commonly used disinfectants, ultraviolet rays, and various radiations. It is sensitive to various antibiotics and chemical drugs to varying degrees, but it has a strong resistance to low temperature and drying. The bacteria can be killed by direct sunlight for several minutes, up to 4 hours. Brucella is very sensitive to heat. It can be killed by moist heat at 60 ~15~30 minutes. The survival time of 0.1% neo gel and 2% lecithin was 30 s and 1-3 min. Brucella was the most sensitive to tetracycline, followed by streptomycin and oxytetracycline.

The main route of transmission is the digestive tract, followed by respiratory skin and mucosa of the reproductive system. When cattle eat feed, drinking water, and milk contaminated by diseased cattle, contact with a contaminated environment, soil, utensils, feces, secretions, and improper disposal of waste, blood, skin, and meat in the slaughtering process can cause infection. Infections caused by the mating of bull cows with diseased cows or diseased cows with cows, inadequate disinfection during artificial midwifery and insemination, and reproductive tract damage caused by artificial insemination are particularly common. Human beings are mainly infected by the lack of disinfection and protection conditions for delivery, care of sick animals, or drinking the milk without disinfection. They have systemic infections and are in the stage of bacteremia. Their meat and viscera contain a large number of pathogens, which can infect processors.

NO.2 Brucellosis in Dairy Cows

Cow brucellosis is an infectious disease caused by Brucella Bovis infection in dairy cows. It not only affects the productivity of dairy cows but also threatens human health. The main infectious sources of brucellosis in dairy cows are sick cows and their fur, milk, urine, and abortive fetuses, placentas, amniotic fluid, etc. Its transmission route is mainly through the delivery of infected cattle. Moreover, people engaged in slaughtering sick animals, milking and other work can be infected by bacteria through the skin damage, but also through the digestive tract, respiratory tract, conjunctiva, sexual organ mucosa infection. China is a country with serious brucellosis infection. In recent years, the infection rate of brucellosis has been increasing year by year. The situation is not optimistic.

Symptoms of Brucellosis in Dairy Cows

The incubation period of brucellosis is generally 14-21 days.
When cows are infected with this disease, the main symptoms are characterized by pathogenic bacteria invading the reproductive system, which can cause inflammation of uterus, peritoneum, joints, testicles, lymph nodes, etc. The most significant symptoms are abortion or infertility in pregnant cows, and some cows also produce stinky secretions from the vagina. If a person suffers from this disease, he will have a fever of 2 to 3 weeks on average, with repeated fever and wavy fever. The patient's whole body is weak, weak, anorexia, white phlegm, can hear the dry sounds of the lungs, joint pain without redness, swelling and fever, muscle pain. Male patients'lesions occur in the genital organs, testicles are enlarged, affecting fertility, and serious cases can cause death.

Diagnosis of Brucellosis in Dairy Cows

Brucellosis laboratories usually use serological tests to confirm the diagnosis. An animal brucellosis tiger red plate agglutination test is generally used in the preliminary screening test. Animal brucellosis test tube agglutination test (SAT) was used for a formal test.

Tiger Red Plate Agglutination Test (RBPT) is mainly used to mix the serum of the tested dairy cows with Tiger Red Plate Antigen (Tiger Red Plate Antigen). After the reaction, the results are determined according to the agglutination degree. If agglutination occurs, it can be judged that brucellosis is positive. If it is positive, it should be further confirmed by the in vitro agglutination test (SAT).

NO.3 Comprehensive control measures

Brucellosis can be treated with antibiotics combined with vitamins, but in order to prevent the spread of pathogens, it is recommended that all infected cows be killed and buried deep. Below are several medication methods for your reference.
(1) Oral tetracycline, 50 mg/kg body weight, 2-3 times/day.
(2) Oxytetracycline tablets, 0.1 g/kg body weight, twice a day.
(3) Kanamycin sulfate, 50,000 units/kg body weight, twice a day.
(4) Gentamycin sulfate, 8,000 units/kg body weight, twice a day.
(5)Oral vitamin C, 10-15 mg/kg body weight, twice a day.

Usually, in order to completely control brucellosis in dairy cows, prevention is the main method.

1. Scientific epidemic prevention
For the cattle rancher, Vaccination is an effective measure to control brucellosis. This method is mainly suitable for high incidence areas of epidemic diseases. Among them, Brucella abortus No. 2 can weaken Brucella strains and have better immune effects on dairy cows. Generally, calves are vaccinated about 6 months after birth and again about 18 months after birth. The immunization period can last for several years.

2. Strengthening the Purification of Epidemic Diseases
For non-epidemic areas, general inspection is usually used. Every spring and autumn, dairy cows should be tested and purified for brucellosis at a rate of 100%. That is to say, every cow should be diagnosed by a serological test. All positive dairy cows must be killed in time, then disinfect their cowshed, and do harmless treatment such as incineration and deep burial to ensure that the purification rate reaches 100%.

3. Strengthening disinfection
At the entrance of each dairy farm, disinfection rooms or channels should be set up. Only after the personnel and vehicles are thoroughly disinfected, can they enter the dairy farm. Sterilize the fence every three days with a 3% disinfectant or 20% quicklime. It is better to do the whole disinfection once a month, including washing the drinking water tank regularly and replacing it with clean drinking water. In addition, the remaining grass and feces in the barn should be cleaned up in time every day. If the feces need to be used as fertilizer, they must be accumulated and fermented before they can be used. Only when the disinfection work is done well can we prevent the possible source of disease pollution and prevent the spread of epidemic diseases.

4. Strengthening the management of the introduction
The introduction of diseased dairy cows is a potential threat to the infection, and the introduction management of diseased dairy cows should be strictly strengthened. In principle, it is suggested that the cattle company should practice self-support and minimize the introduction of cattle from outside.

5. Strengthening personnel management
Brucellosis is a zoonotic disease that can cross-infect humans and livestock. Therefore, it is necessary to strengthen personnel management in farms. Animal breeders should have health certificates and need regular physical examination; due to the residual virulence of various live vaccines to human beings, attention should be paid to self-protection in the course of epidemic prevention; slaughtering animals and cooking animal products in farms should be prohibited; and foreign personnel should be restricted to enter and leave farms at will to avoid unrelated to breeders as far as possible. Personnel enters the farmhouse.

All-round disinfection and harmless treatment through the above means can reduce the incidence of dairy cows, effectively kill brucellosis and reduce the spread of disease.

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