Growers Should Beware Of
(Continued from Pago A 1)
One, a “dry” pox, shows up as
raised, dark skin lesions on the
comb or wattles. There is also a
“wet” form of the pox, which show
up as caseous (cheesy), diphtheric
lesions of the upper trachea and
oral cavity of the birds.
Early dry pox lesions can show
up as blisters, which can rupture.
Soon dark, crusty material forms
on the lesions. The wet pox lesions
show up as caseous pxudate, most
ly on the forward portions of the
trachea when the birds are
examined.
The disease affects primarily
mature birds and is rare in breed
ers, pullets, or broilers, said Zie
gler. It is generally seen in the war
mer summer months but year
round evidence of the disease in
houses has been seen.
“Wc are seeing more of this virus in Pen
nsylvania,” Ziegler told those at the meeting.
In January 0f1996, the lab had seen more than
in the past 12-month period four cases in
all. The virus can have regional variations in
terms of strain, and varies for whatever
reasons.
“Here in Pennsylvania we’re seeing more
than wc usually do, I think,” said Ziegler.
Between Sept. 1995-Sept. 1996, there were
21 cases that were reported to the Pennsylva
nia Diagnostic Laboratories, including wet
and dry cases. Of the 21,18 woe from com
mercial egg layers (11 dry, S wet, and 2 both).
The Midwest and Pacific Northwest see
more of the less- common wet pox, and the
Midwest in general sees more pox cases, for
which research still doesn’t have a reason.
Average mortality for the birds that exhibit
the wet variety of the virus averages 5-10 per
cent, and some growers have seen greater than
30 percent.
Layers are affected by the pox from 29-112
weeks of age. and the average is 50.1 weeks,
according to Ziegler. Thirty-to 35 weeks of
age is most common, he said.
The course of the infection can last from 4
weeks to six months in the house. Production
drops range from I.S-2 percent (the lab has
seen it go as high as 8 percent), and morbidity
is sometimes greater than IS percent (ranges
from 15-20 percent).
There is a small increase in mortality, but
not nearly as bad in the Midwest, which has
been having extensive pox challenges.
The labatNew Bolton has been working on
two different pox treatment projects. One of
them examines the pox virus from a field
strain and looking at why there are varieties of
protection. Is it a “take” problem and does it
have to do with how well the vaccine is admi
nistered (quality of injection site, etc.)? They
are looking into two isolates, including comb
and trachea lesions, and using different pools
of virus. They are looking at company vaccine
protocols and those results.
One finding: combination comb and tra
chea virus vaccines provided protection
against tracheal lesions, but all vaccine proto
cols seemed to protect against tracheal
lesions. More results of the vaccine combina
tions are pending.
The study also looked intently at the associ
ation between poor “takes” or how the needle
vaccine was administered and poor protec
tion. Could protection have something to do
with bird breed types? More work is needed.
, Ip the second study, continuing into the
spring this year, the lab is evaluating three dif
ferent immunity vaccination protocols using
commercially available fowl pox and field
virus with three different breeds. Researchers
are looking at the results of the protocols in
pullets and layers. Vaccines include commer
cially available pox, a field strain, and a
USDA strain.
There were a total of 21 groups of pullets
and layers.
Some early conclusions: all breeds demon
strated protection with field virus used as vac
cination and challenge. But all commercially
available vaccines are very similar, even if
they are mads by diffcrent companies.
Dr. Andre F. Ziegler
•• , HL'fU .
s, & H”'
««4«,•;s t v t H s. t t i 1 i
Possible Fowl
Some of the challenges experi
ences by Midwest growers could
be caused by simple lack of proper
biosecurity measures, not just
from the virus. Sanitary conditions
could preclude their ability to rid
the disease from flocks.
Dr. David Kradel, coordinator
of food safety activities with the
Pennsylvania Poultry Federation,
reminded the growers that con
cerns of biosecurity and keeping
an eye on the latest developments
regarding avian influenza (A. 1.)
should be of utmost concern.
A layer flock was discovered
having a nonpathogenlc form of
AJ, and was depopulated immedi
ately last month. The fear is that
this could be a repeat of the situa
tion of the mid-1980s when a non
pathogenic virus turned pathogen
ic and A.I. decimated millions of
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Pox Challenges In FI
birds in the state.
Another flock is undergoing
testing for evidence of the non
pa thogcnic strain and has exper
ienced some mortality. Some
smaller live bird flocks have
experienced 100 mortality from"
the “nonpathogenic" virus. About
four growers have suffered sub
stantial losses already, many
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IT DOES A
BODYGOOI
guinea fowl.
Biosecurity is tanl
than ever. A guide,"]
the Poultry Industry,
for $l5. It was pub
American Associati
Pathologists.
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the guide by calling
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