What Kind Of Disease Is Avian Encephalomyelitis And What Are The Signs Of This Disease?

Avian encephalomyelitis (A.E.) is a virus-caused disease, occurring in chickens and turkeys at one to three weeks of age, and in adults during the laying period. Unless preventive measures are taken, A.E. can be a source of severe loss in chicken and turkey flocks, in terms of reduced egg production and mortality of young birds infected through the egg. A.E. is spread primarily through the eggs of infected parent stock. It can be spread be direct contact and through the fences.

Signs: In the first stage of the disease, young birds show dullness in the eyes and unsteadiness in walking. As muscle in coordination progresses, the birds tend to sit on their haunches for long periods. When disturbed, they will move about unsteadily, and then come to rest on their haunches again or will fall on their sides. Some birds may refuse to move or will walk on their hocks and shanks. Nervous tremors of the head may be seen, but not always.

The condition of muscle in coordination usually worsens until the birds cannot move about, and this stage is followed by death because they are too weak to obtain feed and water. When handled, the rapid tremors of the bird's body may be felt. An outbreak in mature laying hens or breeder turkeys may not be noticed if only a small percent of the flock is affected. The affected birds, however, will have a sharp drop in egg production during this period and a decline in egg hatch-ability over a period of two to three weeks after infection. Eggs hatched from the infected hens will produce young birds with the above signs. However, when the hens become immune, egg production and hatchability probably will return to normal.