PURDUE    ,    ,
verermory medical
VOLUME 6, NUMBER 2
SUMMER -FALL 1980
An Eye Gland and Bird Immunization
Tear Gland Converted to Antibody Production
An effective program of vaccination in commercial
poultry operations is an essential part of profitable ;
management. In the broiler industry, the early immunization of birds for infectious bronchitis (IB) and Newcastle is a distinct advantage. Management in broiler
grow-out operations involves early exposure of the chick
to an environment recently populated by older birds, a
potential risk for the chick.
Paradoxically, early immunization against IB for chicks
produced from immune breeding flocks is made difficult
due to the transfer of maternal IB antibody through the
yolk. A well-nourished and well-immunized breeding
flock uniformly produces hatch eggs high in maternal
antibody. These serum antibodies of maternal origin
effectively protect the chick, neutralizing virus which
enters the blood stream, but preventing development of
an active, plasmocyte immune response.
The high titer of neutralizing antibody declines during
the second to fourth week. Pullets for a standard laying
flock are^j^naged during this period of falling antibody titei^^strict sanitation and isolation; vaccination
is at six weeks, an age when all birds should have a low
maternal antibody titer. Rroiler management does not
allow for these practices and consequently utilizes two
or three ^^cinations, one at 4-5 days, a second ar
4 weeks, s^Jperhaps a third at 6 weeks.
Age-dependent and individual variations in passive anti
body titer, variable results depending upon the method
of vaccination, expense of the vaccine, and high risk
exposures of the nontmmunized broiler chicks create a
flock health problem.
However, it has been determined that birds inoculated
with IB vaccine on day one post-hatch develop an active
immunity if the vaccine is administered by an eye or
nasal drop method, a modification of the more routine
aerosol method. Vaccine administered to the same age
bird by the drinking water or directly into the blood
does not result in an active immunity. This observation
is even more interesting when one considers that birds
lack well-defined lymphoid tissue, and the cloacal bursa
and thymus, important immunologic organs, are far
removed   from   the   conjunctival   and   nasal   mucosa.
In the late 1960s it was reported that a great number of
plasmocytes and lymphocytes were located in the
subepithelial tissues of the paraorbital gland (para-
ocular gland, Harderian gland, gland of the third eyelid).
This gland, although often called an accessory lacrimal
gland, is the chief lacrimal gland in the chick, being
about 5 times the size and activity of the glandula
lacrimalis. Continuing investigation of this interesting
lymphoid infiltration of this eye gland has led to a
proposal that the oculonasal gland complex be considered equal to the thymus and cloacal bursa in bird
immunogenesis.
Right orbit, eyeball removed, adult chicken, showing accessory
ocular structures. The upper and lower lids have been removed,
revealing edge of periorbital fascia dorsocaudally. 1-paraorbital
gl.; 2-ventral oblique m.; 3-ventral rectus m.; 4-outline of lacrimal gl.; 5-optic n.; 6-interorbital septum.
Support from the USDA has been obtained for an
investigation of the paraocular gland, specifically for
determining timing of lymphoid cell infiltration and
the microstructure which may create a protected environment for B-lymphocyte maturation.
Both field and laboratory information suggest that
the interstitium of the paraorbital gland is unaffected
by  the presence of circulating maternal  IB antibody.
Right eyeball, medial aspect. Paraorbital gland passes from
ventrocaudal to dorsorostral with its duct emptying rostrally,
on the inner aspect of the third eyelid. 1-paraorbital gl.; 2-
ventral oblique m.; 3-ophthalmotemporal a.; 4-scleral anulus;
5-trochlear n.; 6-ophthalmic n.
Exposure of the interstitium to virus seemingly would
occur by trans-epithelial passage, after retrograde passage
in the gland duct which opens to the conjunctiva on
rhe inner surface of the nictitating mem^H|e.
Current research is based upon the working hypothesis
:hat there is a normal, post-hatch migration of bursa-
uepenueiii lymphocylcs iu ihc lamina uiupiia ui die
paraorbital gland. These cells become immunocompetent by interaction with the virus, protected and isolated
from blood-borne, maternal antibody^ka functional
and perhaps structural barrier around tl^^>lood vessels.
At two weeks there are many plasma cells and lympho-
blasts in the lamina propria among a few reticular cells.
The vascular epithelium is limited by a basal lamina and
closely applied to the outer surface of the basal lamina
is one, and often two, laminae of cytoplasm, quite
possibly of reticular cells. Such a barrier does exist in
the thymus (blood/thymic barrier) and an analogous
structure   exists   in   the   brain   (blood/brain   barrier).
The next phase of the investigation is to utilize fluorescent antibody to determine the route for virus transport
across the epithelium, the onset of plasma cell secretion
of specific antibody, and the role of perivascular structures in blocking antibody passage.
Drs. Ronald Hullinger and Roland Winterfield
Poultry Health Programming
Interest in Avian Medicine Gains Momentum at Purdue
The poultry industry is now conceded to be at least two
decades ahead of other sectors of food animal production in nutrition, husbandry practices, and disease
control and prevention. Poultry health programming
by veterinarians specializing in avian diseases has played
a major role in achieving this enviable status around the
world. It is thought to be a model for others concerned
with the food animal sector, in not only the developed
nations, but also the underdeveloped as well.
Unfortunately, the majority of DVM's at graduation are
unfamiliar with the health systems which have contributed to efficient poultry production and which may,
indeed, give predictability to the future of food animal
medicine and the veterinarian's potential role. However,
of interest this past autumn, five senior students at
Purdue enrolled in an avian medicine block (the maximum number which can be accommodated). While this
block is not designed to train a veterinary medical
student to be an avian disease specialist, it does attempt
to broaden the perspective of food animal medicine and
will, perhaps, enhance the student's present knowledge
and futiu||jjjM)rofessional progress in animal agriculture
on a global basis.
Students in the block are introduced to an important
segment of agribusiness through the structure of vertical
integration with lectures and supplemental field trips
to highly successful companies and their related poultry
enterprises. The latest in management technology is
observed first hand and discussions are held with entrepreneurs, executives, and service personnel of the
organizations visited. Newer techniques of flock health
monitoring are being studied and perfected in the
laboratory and field; these serve as a source of valuable
information to the serious student and avian practitioner. Major emphasis is given to advanced diagnostic
methods and disease differentiation through necropsies
and laboratory assistance. Nutritional and metabolic
disturbances of avian species are studied in some detail
since this is an acknowledged weakness of many students
at graduation.
Even within the constraints of time, it has been pleasing
to note the broad spectrum of knowledge the students
have acquired, and which,may have direct application
ich_m
Advanced avian diagnostic techniques and flock health monitoring are emphasized.
to field circumstances. A sense of confidence has been
detected in the students. We feel that a foundation has
been laid for a substantial improvement in the education
of a food animal veterinarian after graduation. In
addition, for the individual desirous of becoming an
avian diseases specialist, a forward step has also been
taken by being exposed to avian diseases and their
management. The future appears exceptionally bright
in the dynamic poultry industry for well-trained veterinarians   -   especially   if  they   are  business orientated.
R. W. Winterfield