Avian -Marek’s Disease

Question 1

What is the causative agent in MD?

Answer 1

Herpesvirus infection

Question 2

Who does MD affect?

Answer 2

Young chickens

Question 3

Why is MD bad?

Answer 3

Causes lymphoma of T lymphocytes and tumors may occur in the nerves, ovaries, tests, viscera, eye, muscle, and skin.

Question 4

How many stereotypes of MD virus are there?

Answer 4

3
Serotype 1 - oncoviruses (tumor causing)
Serotype 2 - non oncogenic virus
Serotype 3 - herpesvirus turkey (HVT)

Question 5

What are the phases of virus cell interaction in which viral replication occurs?

Answer 5

1-Productive infection (non lymphocytic cells)
2-Latent infection (lymphocytes - T & B)
3 - Transforming infection (only T lymphocytes)

Question 6

How is MD transmitted?

Answer 6

Virus is produced only in feather follicle epithelium and spreads by direct contact or by inhaling dust containing the virus

Question 7

Clinical signs of MD

Answer 7

• depression and uncoordination followed by unilateral or bilateral paralysis of legs and wings
• ocular MD decreased pupil size and irregular diameter aka “grey eye”

Question 8

Gross lesions of MD

Answer 8

Can have one or both neural and visceral lesions

• affected nerves will be swollen, gray/yellow
• can have lymphoid tumors

Question 9

Diagnosis of MD

Answer 9

• presumptive diagnosis made on the presence of tumors and observed paralysis
• gross necropsy and histopath are important to make a definitive diagnosis
• PCR also

Question 10

Tx of MD

Answer 10

No effective tx

Question 11

Prevention of MD

Answer 11

Vaccination! Very effective and is given either day 1 of life or in Vivian (3 days prior to hatch)