Markes disease virus, also known as Marek's disease, is a herpes virus that primarily affects chickens and causes tumors in various organs. It was first discovered in 1980 and is transmitted horizontally through inhalation of dander or dust from infected birds. Clinical signs include lethargy, pale appearance, lameness, and tumors in organs like the eyes, nerves, digestive tract, and skin. Diagnosis involves clinical examination, histopathology to detect inclusion bodies, and virus isolation. Control relies on vaccination, biosecurity measures like regular feather removal, and genetic selection of resistant breeds.

1. 1
Tumors in poultry
Markes disease virus
by dr abdelaziz abdelfatah
poultry consultant
Egypt
it is one of aneoplastic viral disease primarly affect
chicken and rarely affect turkey and firstly detection of
the virus occur at year of 1980 by ( dr jozef Marek) and
the virus is belongs to Herpes virus of DNA viruses
this viruses characheterized by the infiltration of
neoplastic cells of cells forming lymphocyt in many
organs as nerves trank and internal organs and most of
the virus type are antigenically related to each other
and greatly differs according to their onchogonisty and
ability to form tumors and some of serotypes are highly
virulant and other are avirulant
the female chicken is mostly affected than male one
some characters related to the virus
.mode of transmission
by horizontal transmission only and
the infection occur through the
respiratory tract of poultry by the
inhalation of the virus which founded
on the epithelial tissue of feather or
skine dander and so it is very
important from our field experience to
burn the collected feather of birds at
time of 80 days old when the feather renewed and
prevent the ability of transmission of this virus infection
and also burn the feather collected every 3 days during

2. 2
egg production
also the virus can infect birds through the digestive
tract by ingestion the contaminated food and water
which affected by the secrection of affected birds
the virus of markes shedes after 6weeks age from
infection and can make post mortum lesion and signs at
day after 80 days old
types and serotypes of markes disease
 .serotype .one
oncogenic strain like
.GA. MD11. MD5. TK. RBIB
low pathogenic strains as
CV1988(RESPINES)
 serotype two
.SBI
 Serotype 3
HVT
infection with markes disease doesnt
mean that the birds will develop tumor as it
depends on
factors belongs to the virus itself.
 dose of the virus inhalled by bird
 virulance of virus during infection
 onchogencity
factors belong to bird itself
 genetic of bird
 age of bird and if the infection occur early
through 2 weeks after hatch or not
 sex of bird
 immunization
.factor belongs to the environment
like hygenic measures and stressfull factors and all in

3. 3
all out of the flock reared in the farm.
clinical signs of Markes disease viruses
.first wave of the virus infection occur to bursa and
thymus gland destroying the mucosal immune system
of bird
.the virus replicate to fully infection form in the feather
follicules
the tumor occur from the virus by malignant
transformation of the lymphocyte in diferent tissues
the general clinical signs of markes is
the bird affected is dull and emaciated
of pale comb and wattle and the feed
and water intake is decresed
in some cases appearance of lamness and dulleness
and most of signs is differs according to the organs
affected as .

4. 4
eye lesion
irregularity eye pubile. and like fish eye and mostly be
unilateral and if bilateral the bird will be blind
anular depigmention in iris which appearanc as grayish
spot loss of intenisty to light
neural form
.if vagus nerve affected the
paralysis occur and
respiratory manifestion occur
and appearance of tumors on
lung tissue like
if nerves of digestive tract
affected so paralysis occur
and appearance of flaccid
crop appearance and
dirrhaee and some tumors
which take whitich
colouration on the mesentery
like

5. 5
if sciatic nerve affected and loss his striation and the
bird take the posture of pallourina posture and this must
differantianted from vit B defieciancy from our
experiance especially the loss of stratian of sciatic
nerve as
visearal form
occur as scatered of tumor in different parts of birds as
heart and spleen and proventriculus and liver which is
very enelarged and kidney which occur in rare form as
Copy right dr .abdelaziz

6. 6
gonadal form
which occur to ovary
destroying the ovary and
make infertility
cutanous form
which occur to feather
follicles and leads to
defeathering of skine and
scatered of alot of it on letter
in farm ground
mortility can be extended for about 40 weeks and the virus
can live in normal atmospher for about 65 weeks and the
birds will be viramic for extended life and the virus itself is
very difucult in its control by sanition as it resistant to phenol
and quantery ammonium cloride
clinical diagnosis of Markes disease in brief
 by clinicopathological examination
 by histopathological examination and presence of
intranuclear inclusion bodies
 by isolation and identification of the virus by agar
gell ppt and using of floresent antibody tech(FAT)
 by differantial diagnosis .
 it should differantiated from some disease make
tumors like.
 lymphoid leuckosis as

7. 7
Markes leuckosis
DNA RNA
Age : Through first one
month old
Through first
one month old
Nerve : Affected Not affected
bursa : Not affected affected
control of Markes
 genetically by genetic selection of breeds which
are more resistant
 environmental factor.... by puting bird in good
hygenic condition beyond the stress and make
good veterinary hygienic measures and removal of
skine collected every 3 days especially after 80
days old chick and burn it make good hygenic
measure to the flock
 by vaccination.
 there is some facts:
about vaccination which repesented in
markes vaccination take 10 days for immunity to birds.
markes disease interfer with the immunity to coccidosis.
live vaccine of reovirus can potenially interfer with the
response to MARKES DISEASE VACCINATION IF THEY USED after
each other directly
adminstration o fowl pox vaccination at one day old
with the markes vaccination is good and preferable and
can give immunostimulation status to bird

8. 8
there is 3 types of vaccination
 serotype one.......is virulant strain vaccine
which is attenuated and called Respines strain
vaccine
 serotype two.....is avirulant vaccine of Turkey
Herpes vaccine(H.V.T)
 third serotype is...... chicken strain which is
avirulant fowl strain
from our field experience we prefer to use the bivalent
vaccine of the Respines and H.V.T vaccine as one
vaccine at one day old chick under skine of neck or I.M
injection in the end of my brief post about markes
disease which i go far from the scientific complication
about markes and mix between my field experience and
the acadimic situation which is written from my
books(poultry disease and hygene for future poultry
consultant part 1. 2 .3)
most of postmortuim photo is belong to me and occur
from my field situation thanks for all
dr abdelaziz abdelfatah
avian poultry consultant
owner of the veterinary lab for disease diagnosis in
elmansourah egypt
References
. field observation of dr abdelaziz
. poultry disease and hygene for future poultry
consuldant...editor of dr abdelaziz abdelfatah
.poultry international magzines