Herpesviridae - Alphaherpesvirinae - Gallid Herpesvirus 2

Question 1

What is the common name of AHV-2?

Answer 1

Mark’s Disease

Fowl paralysis, polyneuritis, neurolymphomatosis

Question 2

Who is the host?

Answer 2

Chickens

Question 3

How is it transmitted?

Answer 3

Highly contagious through inhalation of;
infectious feather debris (very infectious)
dander (less infectious but can survive long amounts of time)
dust.

Question 4

What are the 4 pathotypes and describe them

Answer 4

1) Mild (mMDV): Mostly associated with neural MD. Can be prevented with turkey herpes virus vaccine.
2) Virulent (vMDV): High incidence of neural and visceral lymphomas. Can be prevented with turkey herpes virus vaccine.
3) Very virulent (vvMDV): High incidence of neural and visceral lymphomas. Viruses are oncogenic in HVT vx chickens. Disease preventable with bivalent vx.
4) Very virulent plus (vv+MDV): High incidence of neural and visceral lymphomas. Viruses are oncogenic in chickens vaccinated with bivalent vaccines.

Question 5

What is the pathogenesis of the fully productive infection?

Answer 5

Production of enveloped virions and cell death.
Occurs only in feather follicle epithelium.
Infected T cells appear to be the Trojan Horse by which MDV enters the feather-follicle epithelium

Question 6

What is the pathogenesis of the productive-restrictive infection?

Answer 6

Production of naked virions (not infectious) and viral antigens.
Cell death due to lysis
Occurs in B-cells and activated T-cells
Profound immunosuppression

Question 7

What is the pathogenesis of the non-productive infection?

Answer 7

Viral genome persists in T-cells

No antigens expressed

Question 8

What is the pathogenesis of the non-productive neoplastic infection?

Answer 8

Some latently infected T-cells undergo neoplastic transformation.
MA-TSA appears in transformed T-cells

Question 9

How does susceptibility for Marek’s Disease vary?

Answer 9

Depends on different MHCII haplotypes

Question 10

What are the different MHC II haplotypes?

Answer 10

B19 - Highly susceptible to MD

B21 - Genetically resistant to MD

Question 11

What are the clinical features of MD?

Answer 11

Neurolymphomatosis- lameness, droopy wings, paresis of legs
Visceral lymphomatosis
Ocular lymphomatosis
Cutaneous lymphomatosis

Question 12

Describe Neurolymphomatosis.

Answer 12

Enlargement of nerve trunk- particularly the vagus, brachial, sciatic nerves.
Grey or yellowish in appearance
Usually unilateral

Question 13

Describe visceral lymphomatosis.

Answer 13

Diffuse or nodular lymphoid tumors may be seen in various organs.
Atrophic bursa – absence of tumors helps distinguish from typhoid leukosis.

Question 14

Describe Ocular lymphomatosis.

Answer 14

Graying of the iris - Gray eye, cats eye, pearl eye in one or both eyes
Partial or total blindness
Interference with normal pupil constriction and dilation

Question 15

Describe Cutaneous lymphomatosis.

Answer 15

Plucking of feathers reveal nodular lesions on the skin

Enlarged feather follicles

Question 16

How is Marek’s disease diagnosed?

Answer 16

History and clinical signs
Necropsy
Histo
Serology
PCR
CAM inoculation

Question 17

Is Marek’s disease reportable?

Answer 17

YES.

Question 18

Which vaccination is most widely used?

Answer 18

Bivalent vaccines consisting of HVT (turkeys) and either SB-1 or 301B/1 strains of GHV-3.

Question 19

What is considered the most protective vaccine?

Answer 19

CVI988/Rispens