Marek Disease In chicken, Mark's disease caused by a virus of the herpes type that has the ability to cause carcinogenic disease in chickens, characterized by the leaching of different organs with polymorphic lymphocytic cells.
The occurrence of disease
Mark's disease mainly affects chickens, and it is one of the most important diseases that afflict chickens. It may affect quails to a lesser extent.
The disease occurs most commonly in young and non-adult chickens whose age ranges from (2-7) months, but it may occur at any age after the age of (3) weeks. The disease is found all over the world.
The herpes virus associated with Mark's disease has been divided into three serotypes
The first serotype (Scrotype1).
Isolates of this type are peculiar (isolated from chickens) and differ in their pathogenicity from very aggressive, to nearly non-pathogenic, serotype II.
Isolates of this type are common in chickens and do not cause carcinomas. Serotype3.
Isolates in this pattern are known as turkey herpes viruses, which are common in Turkey and do not cause cancer. The three serotypes have a good antigenic relationship.
- The infected chicken sheds the scales of the feather follicles, which contain the virus, which is a source of respiratory infection for the rest of the chickens.
- The carrier hen may or may not be clinically ill.
- Pregnant chickens shed the virus intermittently during their lifetime.
- The disease is highly contagious and the scales of the feather follicles spread over long distances, which contain.
- The enveloped virus that can infect chickens and this method of transmission is considered the most important.
- The transmission does not occur via eggs and if it does occur it is very rare.
There are clinical signs that appear in chickens with Mark's disease, but they are of limited use in diagnosis.
Chickens affected by organ cancers are often thin and weak before death, chickens in which lymphocytes infiltrate the nerves may be observed partial paralysis, blindness accompanies the infiltration of lymphocytes in the iris, clinical signs are usually noticed before the age of three weeks and are at the highest level at age (2) -7 months.