Mere ‘Science Fiction 9 Now, New Poultry Vaccine Research Proceeds
(Continued from Pag* At)
The development of vaccines
prove a challenge, even for some
of the less challenging, mote com
monly known, less changeable
form of poultry diseases such as
pullorum and Newcastle.
Some vaccines, Donahoe said,
can be made out of bacteria or vir
uses. For vaccines made from vir
uses, the key to making them work
is to create antibodies which coat
the virus, to prevent it from divid
ing, and rendering it harmless to
the bird by preventing it from
replicating. The virus is trans
ferred through the air and enters
the bird's upper respiratory pas
sage. There, the virus can be talmn
into the body by swallowing,
which spreads through the repro
ductive and gastrointestinal
system.
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WHEN ONLY THE BEST WILL DO
Eventually, the virus can escape
into the bloodstream, known as
“viremia,” said Donahoe. The vir
us goes into the liver and spleen,
and this is when the bird can show
early signs of disease it goes off
feed, it doesn't drink the water, and
it becomes “quieter,” Donahoe
said.
When viremia occurs, the bird
mounts a large immune response.
At this time, clinical signs develop,
including swelling eye tissues, the
bird is off feed, egg production
down, and there are any number of
“economic parameters” that show
the producer the bird is infected, he
noted.
A live virus vaccination allows
the bird to develop the large
immune response quickly, though
the virus can’t replicate.
But the response is a shorter per
iod of time (only eight weeks, if
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Hwiling with influenza) compared
to 25 weeks for the killed vaccine.
The killed vaccines use water-in
oil emulsions along with the chem
ically killed, inactive virus. The
killed vaccine continues to gen
erate a very high immune response
in the bird, Donahoe noted.
Donahoe reviewed the early his
tory of developing vaccines, which
began in southeastern Pennsylva
nia and New Jersey in the late
1800 s. hi 1971, one groundbreak
ing event occurred the first
license against cancer, for Marek's
Disease, was obtained. An IBD
vaccine was obtained in 1980, and
new companies and new products
have continue to proliferate in the
decades since.
Now, the industry has to deal
with mergers and acquisitions on
almost a weekly basis, with tech
nology being traded and trans
ferred. And companies ate deve
loping vaccines in a wide variety
of ways. The use of biologicals,
now at IS percent of the share, are
growing. “Biologies are on the
rise,” said Donahoe.
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Possibilities for future vaccines were discussed Monday
by Dr. John P. Donahoe, president of Maine Biological
Laboratories, Watervilie, Maine, left. Donahoe spoke to
about 30 poultry producers and agri-industry representa
tives at the Poultry Health and Management Seminar at
Kreider’s Restaurant near Manheim. At right is John
Schwartz, Lancaster County extension director.
In the past, 11 companies were
making vaccines. Now it’s down
to eight Some are “casualties’’ of
mergers, and they will continue,
Donahoe said. “There are rumors
about cvciy one of them right
now."
Donahoe outlined several major
developments in the forefront of
vaccination development
■ Recombinant DNA vaccines.
The technology focuses in on what
genes are “bad" in live viruses and
takes them out. This includes engi
neering the genes to add antigens
to more foimidably tackle New
castle and bronchitis. “Other
recombinant vaccines are com
ing," he said.
• Competitive exclusion for
biologicals. Using other, less
threatening bacteria can block the
attachments of salmonella and
more threatening bacteria. Dura
tion and delivery of the bacteria is
a problem today, a “goal for
researchers to improve on,” Dona
hoe said.
• Vaccines that can address the
food safety issues that are consum
ing the industry, in light of sal
monella and e. coli outbreaks. A
lot more work needs to be done cm
producing live and killed sal
monella vaccines. But early
research has not been good for
Campylobacter control, noted
Donahoc.
•In ovo vaccines, which
involve highly sophisticated
equipment Vaccines for Malik’s
and IBD could be licensed in ovo,
and many more arc under
development
•DNA vaccines. Instead of
shooting the entire virus into the
bird, take the gene for the antigen
and inoculate the bird. The gene
could be carefully coated for and
correctly implanted in the bird,
with no risk of developing the dis
ease or fear of endotixins. “But this
technology is a long way off,” he
said. “It’s science fiction today.”
Many immunosuppressive dis
eases which cause the bird’s
natural immunities to be jeopar
dized includes bursal, March’s,
chicken anemia, leukosis, and
others. The immunosuppression is
permanent which makes other
pathogens a lot worse to the bird.
•Retroviruses and others,
including J leukosis, where cradi-
cation is needed. Vaccines will be
difficult to develop because of the
changeability of the virus. “Don’t
look for it anytime soon," Dona
hoe said.
• Protozoan vaccines. Vaccines
Lancaster Farming, Saturday, May 15, 1999-A27
for ooccidiosis and other diseases
are becoming important because
the standard drags ate disappear
ing from use. Availability will be
determined on economic viability,
including safety, cross-protection,
and low cost to develop and use.
• Antibody therapy. The idea
“once held great promise,” said
Donahoe. But how to administer
them and not cause allergic reac
tions? There could be a way to
blend the treatment with other
health measures for the bird,
including feed.
• Adjuvants and immune mod
ulation. Researchers are looking
for a way to generate a fast, long
lasting immune response with a
reasonable antigen load.
•Cross-protection, developing
vaccines that can handle so many
different strains of infection, such
as bronchitis, coccidiosis, influen
za, bursal disease, and others.
Researchers must find a way to
develop a cross-protective antigen.
All the labs are working on it, he
noted.
• Vaccines for emerging dis
eases. Exotic diseases and diseases
never present before in poultry will
develop over time and companies
must be prepared.
•Mucosal immunity. Finding
ways to line the gut and reproduc
tive tract with strong mucosal
immunity, a good local cell
mediated immunity, will take
more research. The use of antibo
dies in the digestive tract can be
useful to controlling harmful bac
teria, but the material must be pre
sent on a constant basis. Work to
apply human research in this area
can help.
• Gene insertion. Take the gene
dominant for Newcastle, for
instance, and put it in chicken's
genes. This gene insertion tech
nique “sounds good in theory,"
said Donahoc, but there are prob
lems. It must be near some type of
“regulator” that can allow the gene
to be “turned off and turned on
later," he said. The gene must be
turned on when the chick can
handle it correctly.
“This is big-time science fic
tion,” he said. “We’re a long way
from it, but we’re working on it."
hi the U.S., food safety is a high
priority because of life- threaten
ing outbreaks of diseases such as
salmonella. But in other countries,
salmonella has little if no priority,
because it doesn’t cause problems
with the chickens themselves.
(Turn (o Pag* A 37)