Mycoplasma gallisepticum infection

I. Overview of diseases

Mycoplasma gallisepticum infection in chickens is mainly characterized by respiratory symptoms, such as tracheitis, pneumonitis and so on, so it was once known as chronic respiratory disease. Except for balloon inflammation, it mainly causes infectious sinusitis in turkeys. The infection is distributed worldwide and is also very common.

Mycoplasma gallisepticum has the morphological characteristics of general mycoplasma, negative Gram staining, fermentation of glucose, no hydrolysis of arginine, no energy from urea, sensitive to digitalis saponins, reduction of tetrazole, adsorption of chicken red blood cells, dissolution of sheep red blood cells, no membrane and spots. Mycoplasma gallisepticum has the ability to move slowly, which may be related to its special ultrastructure, that is, there are occasional vesicles at one end of the cell at both ends. Mycoplasma is in contact with eukaryotic cells and moves along the direction of vesicles during movement.

Mycoplasma gallisepticum has low resistance to the environment. Died immediately in the water. It can survive in 20 degrees chicken droppings for 1 Murray for 3 days. They survived for 18 weeks at 37 degrees of yolk and died after 12-14 hours at 45 degrees. Liquid culture at 4 degrees for no more than 1 month, preserved at-30 degrees for 1-2 years, and survived longer at-60 degrees.

II. Popular characteristics

Mycoplasma gallisepticum infection is prevalent in chicken farms all over the world. According to serological investigation, the average infection rate is between 79% and 80%. Besides the pathogenicity of Mycoplasma gallisepticum, the age of chicken is also a factor, and the infectivity of chicken to mycoplasma increases with the increase of age. Concurrent infection has a considerable impact on Mycoplasma gallisepticum infection, even if the pathogenicity of Mycoplasma gallisepticum is not strong, mycoplasma disease often breaks out because of Newcastle disease vaccine or infectious bronchitis vaccine.

Environmental factors also play an important role in affecting the prevalence of Mycoplasma gallisepticum infection. Chicken crowding aggravates the spread of pathogens, and crowding is a kind of stress, which reduces the resistance of chickens. The chicken house is dirty, feces are collected, and the increase in the content of ammonia in the air stimulates the respiratory mucosa, which facilitates the development of mycoplasma.

Undernutrition will lead to the occurrence of mycoplasma disease. There are two main ways of transmission of mycoplasma, which is direct contact, in which small droplets with mycoplasma exhaled by infected birds are transmitted through the respiratory tract to caged chickens or turkeys in the same house. Another way is that the pathogen is transmitted through the eggs of infected chickens to the next generation, which may be more important. In some areas, especially in developing countries, ordinary eggs are often used to culture chicken embryos to produce live poultry vaccines. Mycoplasma transmitted by eggs contaminates the vaccine in chicken embryos and is transmitted to vaccinated chickens after vaccination. The role of this contaminated vaccine in transmission can not be ignored.

Third, clinical symptoms:

The most common symptoms of infection are respiratory symptoms, including coughing, sneezing, tracheal rales and rhinitis. Rhinitis is especially common in turkeys, where one or both sides of the infraorbital sinus are inflamed and swollen, and the eyes are not open in severe cases. Snot is often used to block the nostrils, sometimes the nostrils are filled with mucus mixtures, sick birds shake their heads frequently and are eager to get rid of them, and sometimes they wipe their nostrils with wing fingers so that they are stained with nasal fluid. There is often mild conjunctivitis and clear secretions on the eyes, but sometimes the inflammation of the eyes is also very serious. Sometimes joint inflammation appears toe line, but it is rare that there are people who cannot stand up. The production performance of infected chickens decreased.

4. Differential diagnosis:

As the appearance symptoms of Mycoplasma gallisepticum disease are not unique, attention should be paid to the differential diagnosis of Newcastle disease, infectious bronchitis, infectious rhinitis, synovial mycoplasma infection and chicken cholera when respiratory symptoms occur in chickens. When turkeys appear sinusitis, attention should be paid to the differential diagnosis of chlamydia infection. Some methods of serology and pathogen isolation can be used in differential diagnosis.

5. Prevention and control measures:

Prevention:

At present, there is no breeding flock without mycoplasma infection in our country, it can be said that there is mycoplasma infection in all chicken farms, and there are no obvious symptoms under normal circumstances. Once the stress due to adverse factors, the outbreak of disease may lead to death. Therefore, at ordinary times, we must do a good job in feeding and management, provide balanced feed, pay attention to cleanliness and hygiene, do not allow feces and urine to accumulate in the house, and the cage is not crowded.

Kinds of stress factors:

1. Vaccination is an effective method to reduce mycoplasma infection. There are two kinds of vaccines, live attenuated vaccine and inactivated vaccine.

Attenuated live vaccine: the live vaccine used internationally and domestically is strain F vaccine. The pathogenicity of F Peugeot is very mild, and eye drops inoculation to 1-day-old, 3-day-old and 20-day-old chicks does not cause any visible symptoms or air bag changes, and does not affect weight gain. Simultaneous inoculation with live Newcastle disease vaccine B1 or LaSota strain did not enhance each other's pathogenicity and did not affect their respective immunity. The immune protection is more than 85%, and the immunity lasts at least 7 months.

Inactivated vaccine vaccine: oil-adjuvant inactivated vaccine has a good effect, which can prevent the occurrence of this disease and reduce the induction of other diseases, and increase egg production. It has been reported abroad that the continuous use of two generations of chickens can eliminate mycoplasma infection in the flock.

2. Eliminating the egg-borne transmission of Mycoplasma gallisepticum in eggs is an important way of transmission of Mycoplasma gallisepticum. Blocking this route is of great significance to the prevention and treatment of diseases and is the basis of breeding non-mycoplasma chickens. There are two ways to reduce or eliminate mycoplasma in eggs: antibiotic treatment and heating.

Antibiotic treatment: heat the eggs before hatching to 37 degrees and immediately put them into an antibiotic solution that inhibits mycoplasma at about 5 degrees for 15 minutes; you can also put the eggs in an airtight container of antibiotic solution, draw out some air, and then slowly put it into the air to make the solution enter the egg; there are also cases where the antibiotic solution is injected into the egg.

Heating method: the eggs in the incubator were pressed with hot air to make the temperature rise to 41.6 degrees uniformly within 14 hours, and then moved to the normal hatching temperature to hatch, which can achieve a satisfactory effect of killing mycoplasma in the eggs. But the hatching rate of eggs decreased by 8% / 12%.

3. Cultivate chickens without mycoplasma infection.

Treatment:

At the beginning of the disease, you can try some antibiotics that can inhibit mycoplasma, which can be shaken in the feed or taken through drinking water, or can be injected. The dosage of oxytetracycline and tetracycline is 400 g per ton of feed, Tylosa strain is 2-3 g per 4.5 L of water, and norrimycin is 300-500 g per ton of feed. Taimiangmycin (Zhiyuanjing is a preparation of taimiangmycin) the content of drinking water is 120-500mg/L, no matter drinking water or feed mixing, it will take several days. If the effect of administration is poor, it is necessary to consider the problem of complication, or the relationship between the resistance of the pathogen to the antibiotics used.