Page 23 - AWA-41-No.1 issue

DAIRY FARMING

Think strategically in developing IBDV vaccination programs

nfectious bursal disease virus (IBDV) continues to be a
Ileading cause of economic losses in the poultry industry,
primarily due to immune suppression.1 With the worldwide
spread of IBDV and constantly evolving strains with vary-
ing virulence, vaccination remains a key measure to pro-
vide protection against IBDV, especially against early infec-
tions.1

Developing an IBDV vaccination program should consider
the severity and duration of immune suppression caused
by the virus and may require the strategic use of several
vaccine types, according to Kalen Cookson, DVM, MAM,
DACPV, director of clinical research, Zoetis.
Timing of an IBDV challenge is a key consideration in
creating a vaccination strategy, Cookson explained. Early
infections before 2 weeks of age are often severe and per-
manent. From 2 to 3 weeks of age, the severity of an IBDV
challenge can be variable depending on concurrent stress-
ors or other immune suppressors. Late infections after 3
weeks of age can be moderate and temporary but can still
have a significant impact if other disease challenges – such
as infectious bronchitis, Escherichia coli or inclusion body
Complementing recombinants with immune complex
hepatitis – occur during this window of temporary immune vaccines
suppression, he added.
The strength of recombinant vaccines is their cellular im-
IBDV vaccine options
mune response and cushioning – not completely preventing
Cookson said there are three distinct options for IBDV vac- infections but significantly limiting the number of cycles of
cination in the hatchery: infection and, therefore, tissue damage (atrophy, in this case)
– which translates into protection against immune suppression
1. Recombinant vaccines: modestly cushion the bursa from the IBDV challenge, Cookson said.
and limit – but do not prevent – field IBDV replication.
For immune complex vaccines, besides their convenience,
2. Immune complex vaccines: cause a “take” but are their strength is in better limiting of field infection, better re-
also best at reducing field IBDV replication. duction of field infection pressure and amount of wild type vi-
3. Live vaccines: complement maternal immunity and rus that continues to be shared in the environment, he added.
help bridge the gap to the onset of immunity from recom- By managing IBDV challenge levels more effectively, this “rota-
binant vaccine. tion” tool helps sustain year-to-year efficacy of the all-impor-
tant recombinant vaccines.
Depending on virus challenge pressure and levels of However, the other side of the coin is, because it’s a live vac-
maternally derived antibodies, Cookson said these vac- cine, there will be a bursal “take” – bursa sizes will be more
cine options may complement each other to strategically variable than what is found when recombinant vaccines are
achieve IBDV management goals. used, especially in the three- to four-week range as the vaccine

Live vaccines buy time for recombinants is starting to infect the bursas and cause some bursal atrophy,
he said.
Live IBDV vaccines are complementary to recombinant
HVT-IBD vaccines, Cookson said, explaining that while it Surveillance keeps you informed
is not always necessary to give live IBDV vaccine(s) along Through active bursal surveillance programs, Cookson said
with a recombinant vaccine, when field infection pressure producers can monitor which IBDV strains they are dealing
is very high or the field virus is very aggressive, the addi- with, and at which ages, they are challenging their birds.
tion of live IBDV vaccination to a recombinant program may
help flocks overcome the field virus challenge.2 With that information, an IBDV vaccination strategy can be
developed using the best tools in the toolbox – recombinant,
The reason is the live vaccine provides a blocking mecha- live and/or immune complex vaccines – to minimize the sever-
nism as well as rapid immunity to the birds with the lowest ity of an IBDV challenge and limit immune suppression.
levels of maternally derived antibodies in a flock when they References:
otherwise would start replicating the field virus, he said.
This buys time for immunity from the recombinant HVT-IBD 1 Alkie TN, Rautenschlein S. Infectious bursal disease virus in
to kick in by delaying the field infection window.2 poultry: Current status and future prospects. Vet Med 2016;7:9-
18.
Intermediate vaccines also can be applied in the first
week to help the transition from passive to active immunity 2 Ashraf S, Abdel-Alim G, Al-Natour MQ, Saif YM. Interference
and delay the field pressure to allow more time for the re- between mild and pathogenic strains of infectious bursal dis-
combinant vaccine to provide the bursal and immune sys- ease virus in chickens. Avian Dis. 2005;49:99-103.
tem “cushion”, Cookson noted. Circle 28 on enquiry card
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