Chicken swollen head syndrome

I. Overview of diseases:

Chicken swollen head syndrome is a kind of infectious disease of chickens caused by avian pneumonia virus and secondary infection of pathogenic Escherichia coli, which is mainly characterized by swollen head and characteristic neurological symptoms.

2. Popular characteristics:

SHS is mainly harmful to chickens (broiler breeders, commercial laying hens, broilers) and turkeys. Chickens and turkeys are known natural hosts.

SHS is mainly transmitted horizontally through the angle, and the digestive tract and nasal secretions of diseased or convalescent chickens pollute drinking water and environment, and become the source of infection. The spread rate of the disease is slow. At present, our evidence shows that the disease can spread vertically.

For broilers, the onset age of SHS was 7 weeks in 4Mel, and the peak was 6 weeks in 5MUE. For broiler breeders and commercial laying hens, it could occur at all ages. Without treatment, the course of the disease is about 10 days. If treated with antibiotics and improved ventilation, the course can generally be shortened to 5 days. In recent years, the disease shows a chronic epidemic process. It usually lasts for 2MUR for 3 weeks. The incidence of the disease ranges from 1% to 90%, from 1% to 72% for broilers, from 2% to 40% for laying hens, from 0% to 20% for laying hens, and from 0% to 10% for domestic breeders.

The occurrence of SHS is directly related to environmental factors. SPF chickens inoculated in the isolator can not replicate SHS. Feeding in the environment of high density, high ammonia gas and poor ventilation is one of the pathogenic factors.

Third, clinical symptoms:

SHS, also known as coarse head disease or facial cellulitis, the first symptom of the disease is sneezing, conjunctival flushing, swelling of the lacrimal glands occur within a day, and in the next 12 mi 24 hours, the head begins to appear subcutaneous edema, first seen around the eyes, and then developed to the head, and then spread to the lower pigeon tissue and flesh droop. In the early days, chickens scratched their faces with claws, showing local itching, followed by depressed spirit, unwillingness to move, decreased appetite, and a mortality rate of 1%, 20%, ranging from 1% to 20%. In addition to observing head swelling in broiler breeders and commercial laying hens, they also showed specific neurological symptoms. in addition to extreme depression and coma, most of the disorientated diseases appeared brain disorientation, including continuous and repeated shaking of the head and torticollis. Dyskinesia, movement instability and angle arch reversal and so on. Some chicken heads are tilted upward, showing a "stargazing shape". Sick chickens do not want to move around, and some chickens die because they do not feed. The laying rate and hatching rate of laying hens also decreased, but returned to normal after a few days.

4. Anatomical symptoms:

The first lesion was slight blood stasis in the turbinate mucosa accompanied by sneezing, and then developed to a non-serious extensive color to purple change. in histopathology, the epithelium flattened and the cilia gradually disappeared. subepithelial hyperemia and lymphoid tissue hyperplasia. Subepithelial hyperemia and hyperplasia of gonorrhea were also seen in the lacrimal gland with increased plasma cells. Although mild ecchymosis spots and decreased ciliary motility may be observed in the upper respiratory tract, the trachea is generally not affected in the acute phase. The swollen head of a diseased chicken is caused by subcutaneous edema and dilatation around the orbit. In a serious case, cyanosis and swelling of the flesh beard, swollen head, yellow edema to suppuration of subcutaneous tissue can be seen after peeling off the skin, and the naked eye lesion remains normal, but the eyelids are closed due to water and conjunctivitis. The disease can produce tracheitis and sometimes pulmonary necrosis. histological examination showed that there were lymphocytes and heterophil accumulation in edema.

5. Prevention and control measures:

1. Hygienic management measures: changing the sanitary conditions of the chicken house, reducing the feeding density, reducing the concentration of ammonia in the air, and increasing the ventilation rate of the chicken house have a good effect on preventing or reducing the occurrence of diseases and the degree of harm.

2. Prevent the secondary infection of bacteria: after poultry is infected with virus, on the one hand, it can reduce the pain-free power of poultry, resulting in a decline in resistance, on the other hand, the infection of virus in the upper respiratory tract epithelium destroys the integrity of epithelial cells, so it is easy to be secondary to a variety of bacteria such as Escherichia coli, Pseudomonas aeruginosa and so on. Therefore, furans, sulfonamides and broad-spectrum antibiotics can be taken orally, and the effect of adding vitamins and electrolytes will be better.

3. Application of vaccine: Morley (1984) could resist the attack of the same virus when a strain attenuated by 50 generations of chicken embryos was used in 4-week-old chickens. A year after the vaccine was widely used in South Africa, SHS rarely occurred. Spray immunization of 1-day-old commercial broilers can achieve moderate economic benefits and immune response, and significantly reduce the incidence of clinical treatment. At present, inactivated demulsified vaccines and attenuated vaccines are available in European countries. There is no such report in our country. In addition, it is considered that the use of NDV-EDX76 and SHS virus quadruple vaccine can effectively prevent the occurrence of diseases.