Report on the Agricultural Experiment Stations, 1953 Page: 16
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16 REPORT ON EXPERIMENT STATIONS, 1953
ing on a program of flock vaccination using an egg-propagated virus
which in turn is inoculated into "seed" birds that transmit the protective
virus to the rest of the flock. The data on 3- to 6-week old groups
indicate that exposure of birds in this way during the period mentioned
is highly practicable.
At the New Hampshire station a concentrated effort has been made
to select a vaccine strain for infectious bronchitis, and one has been
found that is apparently safe and has promising immunizing properties
under laboratory conditions. It has been found possible to
combine this strain with the B1 strain of Newcastle virus and immunize
birds against both diseases, using a spray technique under laboratory
conditions. Field trials of this technique are now under way.
California station veterinarians are experimenting with a new program
of 100-percent immunization against infectious bronchitis of
approximately 100,000 chicks. All chicks in a flock are inoculated
between 4 to 16 weeks (optimum age 6 weeks) while they are still
under brooder heat and before vaccination for other diseases. Chicks
get over the disease in 2 weeks and are thought to be immune for
life. Search is being made for a vaccine that will produce immunity
without any harmful effects on the birds.
The New York (Cornell) station is continuing its attempt to lessen
virulence of the bronchitis virus by yolk-sac cultivation. Three
experiments with adapted bronchitis virus of reduced virulence have
been carried out without loss of the immunizing value of the virus.
They also report that eggs from flocks recovered from bronchitis
may be hatched without disease transmission to the chicks.
Chronic respiratory disease
Preliminary findings have grown out of the cooperative studies
(stations and USDA) on chronic respiratory disease reported last
year. These serve to clarify the thinking that exists regarding socalled
"air-sac disease" in chickens. The causative agent is apparently
a pleuropneumonia-like organism. The Massachusetts station, as
well as others, has noted that onset of the disease is usually slow, and
its course is protracted. In uncomplicated outbreaks, the respiratory
symptoms and lesions occur in the upper and lower respiratory tract
with striking involvement of the air-sacs. Growth of the bird is
slowed and there are some deaths. When the disease it further complicated
with Esecherichia coli, Newcastle disease, or by infectious
bronchitis, the outbreak becomes very severe and many birds die.
Although frequently termed air-sac disease, the condition may
actually be a combination of diseases.
Chronic respiratory disease is reproducible experimentally in
chickens and other avian species. The agent can be propagated in
embryos and produces characteristic lesions in the region of the joints
and in the lower respiratory tract including the air-sacs. Carriers
have been detected among survivors of an outbreak. The disease
agent is penicillin-resistant but is more sensitive to some of the other
common antibiotics, especially under laboratory conditions. In a
recent report by the Storrs station (Connecticut), it was shown that
terramycin in mineral oil, injected subcutaneously, helped in the treatment
of this disease in two groups of pullets.
Better diagnostic techniques are needed. The Washington station
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1953, book, 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5989/m1/18/: accessed February 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.