MAREK’S DISEASE

a Herpes virus infection of chickens, and rarely turkeys in close association with

chickens, seen worldwide. From the 1980s and 1990s highly virulent strains

have become a problem in North America and Europe.

This includes different pathological entities; classifies as:

Lymphomatosis1. Visceral - big-liver disease2. Neutral – paralytic symptoms of legs and

wings3. Ocular - gray eye, pearly eye ; is

charactirized by the blindness and misshaped pupil.

4. Osteopetrotic - white tumors along the sternum and liver

Occurrence

has been reported from all parts of he world. It has caused great loss

to broiler and breeder farms throughout.

Cause of Disease

Was known as “range paralysis”. Describes by Dr. Joseph Marek in 1907 in Europe, this disease was reported in the United States in 1914. it was in 1967 when the causative agent was established positively as a Herpes Virus related to those which cause shingles and cold sores in man.

it lacks the outer envelop which characterizes many other virus.

virus completes itself by acquiring its outer covering in the feather follicles.

it multiplies rapidly, producing characteristic signs of Marek’s disease.

the virus remains until death of bird.

Signs• Paralysis of legs, wings and neck.

• Loss of weight.• Grey iris or irregular pupil.

• Vision impairment.• Skin around feather follicles raised and

roughened.

Post-mortem lesions

• Grey-white foci of neoplastic tissue in liver, spleen, kidney, lung, gonads, heart, and skeletal muscle.

• Thickening of nerve trunks and loss of striation.

• Microscopically - lymphoid infiltration is polymorphic.

Prevention• Hygiene, all-in/all-out production, resistant

strains, vaccination generally with 1500 PFU of HVT at day old (but increasingly by in-ovo application at transfer), association with other strains (SB1 Sero-type 2) and Rispen's.

It is common practice to use combinations of the different vaccine types in an effort to broaden the protection achieved. Genetics can help by increasing the frequency of the B21 gene that confers increased resistance to Marek's disease challenge.

Erythroblastosis

• a blood disease characterized by the abnormal presence of erythroblasts in the blood.

Granuloblastosis• (veterinary medicine)An avian leukosis

characterized by the presence of excessive numbers of immature granulocytes in the blood of affected birds.

ERYTHROBLASTOSIS

• 337.338.Erythroblastosis (ER) Is Characterized By Intravascular Proliferations Of Immature Precursors Of Erythrocytes. ER Has A Leukaemic Character And Is Manifested With Signs Of Severe Anaemia. The Liver And The Kidneys Are Moderately Enlarged With A Characteristic Dark Red To Mahogany Colour, Sometimes With Haemorrhages.

• • 339.ER Is Caused By The Avian Eryhtroblastosis Virus (AEV); The

Most Frequently Encountered Strains Are E-26, ES4, R Etc. The Spleen Is Unusually Enlarged Or Atrophied In Cases Of Severe Anaemia.

• 340.Histologically, Accumulation Of Erythroblasts In Blood Sinusoids And Capillaries Is Seen. The Diagnosis Is Based On Visceral Histological Lesions, Typical For ER And Peripheral Blood Haematological And Morpho¬Logical Analysis.

• 341.342.Osteopetrosis Is A Neoplastic Disease, Aetiologically Related To The L/S Group Of Viruses. It Is Characterized By A Significant Thickening Of Bone Periosteum. The Diaphyses Of The Tibia And/Or Tarsometatarsal Bones Are Most Commonly Affected. Often, Osteopetrosis Is Seen Simultaneously With LL In The Same Bird.

Myelocytomatosis

• one of the virus-induced diseases in the leukosis-sarcoma group of diseases of fowl. It is characterized by tumors of the skull, ribs and limb bones. There is emaciation, weakness, pallor of the comb and a course of several months. There are often bony protuberances at the head and on the thorax and shanks.