Infectious bronchitis control Immunization of chicks

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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