This document provides information about Marek's Disease, including: 1) It is a lymphoproliferative disease of chickens caused by the Marek's Disease Virus (MDV), a herpesvirus. MDV has three serotypes, with Serotype 1 including the oncogenic strains responsible for Marek's Disease. 2) The virus spreads via dander from infected feather follicles through the air. It causes proliferation of lymphocytes which can deposit in various tissues, leading to neural, visceral, cutaneous or ocular forms of the disease. 3) Clinical signs include paralysis, enlarged organs, skin nodules or eye protrusion. Diagnosis involves post-mortem

1. Marek’s Disease
Suggested By Submitted By –
Dr Neeraj Gangwar
Saroj Kumar
Dr A.K. Srivastava
6th sem, B.V.Sc & A.H
Department Of Veterinary Pathology
DUVASU , Mathura

2. Introduction
• Marek’s Disease – A lymphoproliferative disease
of chickens characterised by mononuclear
infilteration of PNS, other tissues & visceral
organs.
• First described by Jozsef Marek of Hungary in
1907.
• Due to neuronal involvement, synonyms used
are – Polyneuritis, Fowl Paralysis, Range Paralysis
& Neurolymphomatosis.

3. Aetiology
• MD – caused by Herpes Virus – enveloped, dsDNA
virus.
• MDV – classified into 3 serotypes –
• Serotype 1 – includes oncogenic strains of MDV.
• Serotype 2 – includes naturally non pathogenic
strains.
• Serotype 3 – antigenically related to herpes virus of
turkey (HVT) . Used for production of vaccine k/a
HVT 126.

4. •
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Serotype 1 – subdivided into 3 pathotypes –
Mildly Virulent (mMDV)
Virulent (vMDV )
Very Virulent (vvMDV )
Virus infectivity is strictly cell associated except in
feather follicles epithelium where cell free virus are
produced.

5. Spread
• Virus is present in desquamated feather follicle
epithelial cells, oral, nasal, tracheal secretions.
• Feather follicles – main source of infectivity of
dander.
• Air borne route – most important route.
• Virus is not transmitted through egg.
• Infected birds continue to contaminate the
environment by shedding virus.

6. Epidemiology
• Genetic constitution – greatly influences pathology
& incidence of disease.
• Genetic resistance is of 2 types –
• Associated with major histocompatibility complex
allele. (B21)
• Susceptibility of T cells to transformation.
• Females are more susceptible than males.
• Stress – main environmental factor.

7. Pathogenesis
MD Virus enters into body in lymphoid organs
Proliferate & cause viremia
Reaches site of prediliction
Virus after proliferation get depositted in feather
Follicle
Here dander like material is produced which acts as
source of infection

8. Asymmetric Paralysis
Torticollis

9. Ulcers in feather
follicles
Swelling Of Wattle

10. • MD Virus effect T cells & cause their
pleomorphy.
• 2 types of cells are produced –
• Immature pleomorphic type leucocytes
• MD cells – Degenerating lymphoblast cells

11. Paralysis of wings
Spatic Paralysis

12. Forms Of Disease
• Visceral form –
• Proliferation of lymphocytes & are depositted in
visceral organs ( kidney, liver, spleen, gonads).
• Tumor may be nodular or diffused.
• Organs – very much enlarged & hard in consistency.
• Neural form –
• Proliferating lymphocytes depositted in PNS effecting
sciatic & brachial plexus.
• Nodular formation in nerve cause unilateral /
bilateral paralysis , striations are lost in nerves.

13. Visceral form
Neural Form

14. • Cutaneous form –
• Proliferating lymphocytes get depositted in skin
producing nodular type lesions.
• Occular form –
• Protusion of eye ball, looks pearl like.

15. Occular Form
Abnormal pupil size

16. Diagnosis
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PM Findings
Age
Symptoms
Radial Immunodiffusion Test
MATSA ( MD Associated Transforming Surface
Antigen) – Non specific MD virus Ag, also present in
HVT vaccinated chicken. It is diagnostic Ag.

17. Thank You