This decline comes to last three weeks, after which the production returns to ascend slowly.

Epidemic tremor: Avian encephalomyelitis (AE) is a common viral infection that causes head and neck tremors and progressive ataxia (a lack of muscle control or coordination of voluntary movements) in young chicks between 1 and 3 weeks of age. Symptoms appear in chicks around seven days of age.

The clinical picture varies depending on the age of the infected birds. In adult hens, avian encephalomyelitis causes only a marked drop in egg production. This decline lasts for three weeks, after which production slowly begins to rise again.

The chicks walk unsteadily, with weak legs, causing them to appear as if they are sitting or standing on their tarsi. When encouraged to move, they exhibit muscle incoordination that progresses to flaccid paralysis of the legs and prostration.

The impossibility of movement causes the chick does not eat food, and then we come upon the death.

The disease is caused by an integer virus, called encephalomyelitis virus avian (VAM). Often, the first sign of infection in chicks is depression, followed by loss of coordination, collapse of the wings, muscle tremors, fast of the head and neck (less common, in the wings and legs), sitting on the hocks and fall on their side.

Chicks can also become paralyzed, and they are often found lying on the ground in a state of severe weakness. We need to step in to ensure that the chicks stay hydrated and continue to eat; otherwise, they will often starve to death or be trampled to death by other members of the flock.

It is possible that some chickens are only affected slightly and recovered in full. The chickens are older or who are infected with AD often do not show clinical signs of being infected, except for a decrease in occasional production of eggs in laying hens.

The chicks that are retrieved from the AE may have problems of coordination, continuous, be blind permanently in one or both eyes and have a greater risk of developing cataracts. There have been many other incidents in which the chicks are born of chickens that have been recovered from an AD they go blind for no apparent reason.

Transmission:

The AE is transmitted to the lots through various ways:

• Introducing a new chicken—often an older one—into a flock or group that is a subclinical carrier of the virus or has recovered from an outbreak.
• The breeder hen is infected with the virus and transmitted it to the chick freshly hatched from the egg, through vertical transmission. If the eggs hatch, about 25 % or more die just prior to hatching. The chicks hatched that are infected with AE generally develop signs of infection between one day and three weeks.
• The infected chickens shed virus in their feces, which contaminate the environment and are ingested by other members of the flock. The virus is shed in the feces of chicks infected for a maximum of 2 weeks.

Incubation period:

Chicks infected by vertical transmission of the eggs begin to develop clinical signs between one day and three weeks after hatching. When infected by direct contact with sick birds, signs of infection may take at least 11 days to begin to arise.

Clinical signs:

Tremors in the head. Induces progressive. Depression. Boredom. Sitting on the feet or hocks. Lying down. Lying to one side. Weakness. Blindness. Death.

Prevention:

Prevention: Live vaccination:

Pullet-breeding of 10 to 15 weeks of age to prevent the vertical transmission of the virus to their eggs and to provide for their offspring immunity maternal against the disease.