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Infectious Bronchitis Control
immunization of chicks by willful infection protects laying
hens from disease which may be costly to table egg producers
A. S. Rosenwald and D. V. Zander
The following article is a report of progress in mature laying flocks were immune, many flocks in the area a challenge-test was
a long term field study conducted by the Uni- growing flocks were susceptible and done. Three to six representative birds
versity of California. The laboratories of the
California Department o f Agriculture cooper- needed protection. -from each of several age groups on
ated with counsel and by making determina- co-operating ranches-were shipped to
tions of disease conditions during these trials. Davis. Each bird was inoculated intra-
Farm Advisors W . F. Rooney, Tulare County, Willful Infection Trials tracheally-in the windpipe-with IB
Ralph Pfost, Fresno County, W . W . Mitchell,
Sacramento County, and Dr. M . A . Nilson, act- Field trials were started in 1952 to de- virus as illustrated by the photograph.
ing extension poultry pathologist, helped plan termine if a program of immunization If the birds were immune, no symptoms
and conduct the trials. by willful infection of the chicks before developed. If they had not had bronchitis
Infectious bronchitis - IB - was they began to lay would fill the need in
California as a similar program has in
and were not immune, there would be a
first recognized in California as a dis- take. That is, the birds would sneeze,
ease of young chicks which occasionally many other states. In Massachusetts- gurgle or cough.
caused high mortality but resulted in a the first state to use this plan-over three All replacement chicks on ranches
lasting immunity in recovered birds. million pullets were immunized in 1953, where the adult layers were immune were
There is considerable evidence that by swabbing the windpipes of a small willfully infected-immunized-with IB
uncomplicated IB is not of major con- per cent of the birds with IB virus and virus.
cern to fryer producers since it results allowing the infection to spread. Detailed records were kept for two
in only minor or temporary setback in The California trials were organized weeks and general effects were noted for
the growth of chicks. Death loss from on an area basis with the Orange Cove- the duration of the trial.
IB has not been a serious problem. It Orosi area-in Fresno and Tulare coun- To determine if the immunity induced
is of greatest importance as an economic ties-selected for the first series of was satisfactory to prevent a drop in egg
hazard to table egg producers. experiments. Infectious bronchitis in lay- production certain growers submitted
In California, the greatest need has ing chickens had been definitely diag- their flocks to IB challenge on the ranch
been to prevent outbreaks of hronchitis nosed in that area. Most of the a year later.
in laying hens because it is in this group poultrymen produced table eggs and all In 1952 there were 87 age groups of
of birds that economic loss due to dis- the growers wanted information on im- chickens-from 34 flocks-tested for im-
rupted egg production and lowered egg munization. Also, it is well isolated from munity to bronchitis by challenge. Based
quality has been most severe. Birds that other poultry areas by extensive fruit on the challenge-test results, 62 groups
have not had the disease as chicks are or field crop operations or by mountains were immune, nine were not immune,
still susceptible when they come into the with the prevailing winds toward the and 16 were questionable-where one or
laying period. mountains. The number of birds in- two birds in the test group developed
A state-wide survey in 1951 indicated volved were within the limits of practical bronchitis-had takes-while the other
that the diesase was present in all major field experimentation. chickens did not.
poultry producing areas and, while most To determine the immunity status of Because of the number of questionable
Inoculation of chick with infectious bronchitis virus. A few drops of the virus fluid are squirted into the windpipe.
12 C A L I F O R N I A AG R I CU L T U RE, J U N E , 1 9 5 5
groups, it was decided to inoculate intra- poor management or brooder failure These trials were begun before any
tracheally all of the growing chicks- contributed to high mortality. commercial IB vaccines were available
before 14 weeks of age-in each brood On-the-ranch challenge of the laying and-as of May 1, 1955-no effective
of laying bird replacements to be immu- hens-9-12 months after their inocula- immunizing strain of infectious bron-
nized. This 100% inoculation was done tion as chick-howed that the im- chitis virus is available which does not
to insure that each chick would become munity induced provided adequate pro- cause symptoms following its use on sus-
infected and develop immunity. tection during the following laying year; ceptible birds or which does not spread
Challenge of laying flocks which as challenge did not affect egg production from the vaccinates to susceptible birds
chicks had gone through a natural out- or quality. Similarly, field outbreaks of nearby.
break-as well as those inoculated lOO‘i;, definitely diagnosed bronchitis resulted
in the trial-indicated that good protec- in satisfactory protection as shown by
later challenge of such flocks except that Satisfactory Control
tion was obtained through at least a year.
To conserve time and costs it was in one such case there was a very slight The data obtained from over 315,000
decided in 1953 to test the practicability drop in production. chicks in broods with takes indicate that
of inoculating 10% of each brood and The lowest mortality reported in the the Massachusetts L-43 strain of IB virus
allowing the infection to spread to pen- trials-O.O% for the two weeks following. used in the trials by veterinarians on an
mates, thus inducing immunity through- inoculation-occurred in chicks inocu- area basis-after the immune state of
out the brood or group. As was the case lated 100% at two weeks of age and with all flocks had been determined-pro-
in previous years, such flocks showed no good takes. However, there is a definite vided satisfactory control of infectious
drop in production or any adverse effects indication from the data that the mor- bronchitis in laying hens. The cooper-
when challenged-on the ranch-1 1 tality from all causes for the two week ating poultrymen were thus protected
months after this type of immunization. period following inoculation was much against economic loss.
lower in chicks inoculated at five weeks It must be emphasized that this
of age or older than in chicks inoculated method of immunization is not without
Rio Linda Area at three to four weeks of age. It was also hazard, since the virus spreads-as do
Following the satisfactory results in obvious that IB virus should be used other symptom-producing IB viruses -
Orange Cove-Orosi, poultrymen in the only on growing birds in good health. to susceptible birds in the area. It should
more intensive poultry area of Rio Linda IJS use on chicks infected with other therefore be used only under carefully
offered their cooperation to obtain ex- agents may precipitate increased losses. controlled conditions.
tensive data. Where all chicks in a brood were inoc- The goal must be to find vaccines and
The Rio Linda area was organized ulated directly into the windpipes, the methods which produce immunity-
along lines similar to those of Orange symptoms occurred within 24-48 hours without perpetuating the diseasewith
Cove-Orosi. The assistance of veterinary and were over within a week or tcn days a view toward its elimination. Research
practitioners in each area was enlisted to except where prolonged by complicating is continuing on this and other infectious
do the immunization. To coordinate the respiratory infections. When only 10%- bronchitis virus strains as immunizing
trials, a steering committee of poultry- 20% of the brood were similarly treated agents.
men was formed in each area. Only 10% and the infection allowed to spread, the
A . S. Rosenwald is Extension Poultry Pathol-
of the birds were actually inoculated in beginning of marked signs oceurred a ogist, University of California, Davis.
each of the broods to be immunized. little later and the duration of the out- D. V . Zander is Assistant Professor of Vet-
A survey by challenge of the laying break spread out over a longer period. erinary Medicine, University of California,
flocks to be included in the Rio Linda Results of the trials indicate that under Davis.
area showed that all were immune. Thus the conditions encountered in the two The above progress report is based on Proj-
the trial and inoculation could go ahead test areas willful exposure of 100%- ect No. 3966.
without endangering any susceptible lay- or of 10% of the birds in replacement The strain of infectious bronchitis virus
ing flocks. Cooperating flock owners flocks-by inoculation with Massachu- used for both challenge and inoculation and
could have groups of replacement chick- setts L-43 strain of infectious bronchitis designated Massachusetts L 4 was obtained
from Dr. Henry Van Roekel of the University
ens challenged by veterinarians to de- virus provides adequate protection dur- of Massachusetts. Since October 1953 the virus
termine the immunity status. If a group ing the first year of production. The used was prepared and donated for the trials
proved to be resistant to IB-as a result procedure as carried out proved eco- by the Cutter Laboratories, Berkeley. Prior to
of a natural outbreak-inoculation was nomical and practical. It was not con- that time the v i r w was prepared in University
of California laboratories at Davis.
not done. Thus, there were more flocks sidered to harm the welfare or income
The poultrymen in both areas and Drs. Ian
in the trials than are shown in the table of the few fryer producers operating McDonald. Jack Pjlock, and S. F. Exstrom co-
because broods immune on challenge- within the trial areas. operated in the trials reported.
therefore not inoculated-are not shown.
Results of Willful Infection Trials
Results of All Trials Totals Inoculated Flocks w x takes
Trial
The over-all mortality from all causes Mortalit Mortalit
Flocks Birds 2 wk. post Lo,. 2 wk. post rnoc.
for the two weeks following willful in-
. ... .
~ ~~
fection was about 1% the range was be-
; 100% 77 84,505 91 1 1.08% 69 77,355 851 1.10%
Orange
tween 0% and 8.5%. Chicks in 86.8% Cove-Orosi
of all flocks inoculated developed symp- 1952-1953
toms while in the remainder there were 10% . . . . . . 59 64,110 401 0.63 46 50,090 383 0.77
no, takes. Orange
Cove-Orosi
A careful check revealed that con- 1953-1955
current infections-Newcastle Disease,
chronic respiratory disease, or others- 10-20Yo
Rio Linda
. . . 89 213,726 2,735 1.28 78 188,820 2,452 1.29
were present in many of the broods 1953-1954
where mortality following immunization
exceeded 1%to ll/z%. In some broods,
Totals . . . .225 362,341 4,047 1.12% 193 316,265 3,686 1.16%
CALIFORN I A AGRICULTURE, JUNE, 1955 13
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