Avian encephalomyelitis is an infectious disease that damages the nervous system. Chicks are most likely to occur, characterized by ataxia and tremor. Especially in the head and neck, also known as "epidemic tremor.". The laying rate of laying hens decreased.
Avian encephalomyelitis virus (aemv) is an intestinal ribonucleic acid virus, which can be isolated from the brain of sick chicks. The virus has strong resistance, 20% quicklime, 5% bleaching powder, 5% carbolic acid, 2-5% formalin can inactivate it within 10 minutes.
Chickens of all ages were infected, and chickens of 1-6 weeks old were more likely to be infected. Pheasants and quails can also be naturally infected. The disease can occur all the year round, but it often occurs in the peak period of brooding from January to June. Virus transmission, one is through the egg vertical transmission, in the shell before the chicken embryo stage infection, after the shell disease. The other is horizontal transmission through fecal detoxification during brooding stage. The virus spreads rapidly, sometimes almost entirely. The incidence rate of chicks is generally 60-80%, with a mortality of 10%. Turkey is also infected, but the symptoms are not obvious, the performance of egg production rate decreased, abnormal eggs and so on.
Most of the patients with clinical symptoms were at the age of 1-2 weeks old. They began to lose their spirits and their eyes were dull. Then they appeared dyskinesia, swaying back and forth, shaking their heads and necks. Sick chickens refused to walk. They were forced to drive and walk with their legs. They were prone to tilt or sit back, and some of them moved in circles. Some screamed, rushed forward and stopped when they hit obstacles. In some cases, the lens is turbid, the pupil reflex disappears, and the sick chick finally becomes paralyzed or fails to die. There were no clinical symptoms in the large and adult chickens. The laying hens dropped sharply in 1-2 weeks, some of which could reach 20%.
The pathological changes were as follows
It is difficult to observe the general pathological changes with naked eyes. Only by collecting the brain and spinal cord for histopathological examination, degeneration of nerve cells, cell infiltration around blood vessels, and lymphoid cell hyperplasia nodules in parenchymal organs can be seen.
According to the epidemiology, clinical symptoms and histopathological changes, comprehensive diagnosis was made. Agar diffusion test should be done if necessary.
It is mainly differentiated from nutritional encephalomalacia, vitamin B1 and B2 deficiency, Marek¡¯s disease and rickets.
Prevention and control measures:
At present, there is no effective treatment. It is a good measure to improve the feeding environment, strengthen the disinfection of pens and isolate sick chickens in time. Traditional Chinese medicine can effectively control the disease.