An update on Marek's disease

52 Pages·2017·2.23 MB·English

by  April D. Norris

An update on Marek’s disease
Isabel M. Gimeno
Content
• Marek’s disease (MD) and Marek’s disease virus
(MDV) evolution
• MDV-IS: the newest challenge of MDV infection
• MDV-induced tumors:
• Analysis of a MD outbreak- what to do
Content
Marek’s disease (MD) and Marek’s disease virus
(MDV) evolution
• MDV-IS: the newest challenge of MDV infection
• MDV-induced tumors:
• Analysis of a MD outbreak- what to do
MD evolution
HVT HVT+SB-1 CVI988
1907 1960 1970 1981 1992
Jozef Marek, 1907
• Tumors in vaccinated chickens
Major disease • Tumors in genetically resistant chickens
Minor Disease
Neoplastic in nature (tumors) • Non neoplastic syndromes
Inflammatory in nature
Peripheral nerves, viscera, skin • Neurological (transient paralysis)
Only peripheral nerves
High mortality • Vascular (arteriosclerosis)
Low mortality
Major economical impact • Panophtalmitis
No economical relevance
• Immunosuppression
MDV evolution
100
90
80
70
k
n
a
60
r

e
c 50
n
e
l 40
u
r
iV 30
20
10
0
1990’s-on
1960’s 1980’s
vv+MDV
vMDV vvMDV
From: R.L. Witter. Increased virulence of Marek’s disease virus field isolates. Avian Diseases, 41:149-63, 1997
MDV evolution and consequences on MD
100
R.L. Witter
x
90
e
d
n 80
i

n
70
o
i
t
a 60
t
s
e 50
f
i
n
40
a
m
30

l
a
c 20
i
n
i 10
l
C
0
m v vv vv+
MDV pathotype
Inflammation Tumors Immunosuppresion
Causes for MDV evolution
• Changes in the production system
• Backyard – Large integration
• Vaccines do not protect against superinfection or
against MDV transmission
• Recent studies
• Chicken genetics
• Inmunization against MDV
Vaccines and MDV evolution
Rispens ?
HVT+SB-1
vv+
HVT
vv
Relative
v
virulence
m
1940 1960 1980 2000 2020
R.L.Witter
Features of highly virulent MDV
• Overpass vaccine immunity
• Induce tumors in other species (turkeys)
• Induce tumors in resistant lines of chickens
• Induce a variety of syndromes both neoplastic and
non-neoplastic (very complex disease)
Syndromes associated with highly virulent MDVs
Neuritis
Tumors
Arteriosclerosis
(Lymphomas)
Panophtalmitis
Transient
immunosuppression Permanent
Immunosuppression
Transient
paralysis