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Problems Arising in the Control of Bacillary White diarrhea*
POULTRY SCIENCE VOL. V
AUGUST-SEPTEMBER
No. 6
BY L . D . B U S H N E L L AND W . R . H I N S H A W
Department of Bacteriology Kansas State Agriculture Experiment Station This is a subject which has become more a n d more i m p o r t a n t with the increase in p o u l t r y population in the country a n d with the r a p i d transfer of p o u l t r y breeding stock from one locality to another. The problem m a y be considered from three angles—that of the laboratory worker, t h a t of the practical p o u l t r y producer a n d t h a t of the commercial hatcheryman. The relationship between the three groups must be close, otherwise no actual progress can be expected in the eradication of this disease. Below are enumerated some of the facts which should be brought u n d e r very careful study. 1. A standardization of the test. 2. The proper individual who is to make the test. 3. The development of an improved method of field diagnosis. 4. A correlation of the test with carefully controlled field results. 5. Factors predisposing to infection. 6. Influence of the incubator upon the spread of the infectious material. 7. A study of the rôle of the infected male, in the dissemination of the disease. 8. The minimum percentage of reactors which may be considered safe. 9. The amount of infection contracted by adults and the influence on dissemination of the disease. 10. Modes of introduction of the disease from the outside. 11. Methods of sanitation necessary for the control of the disease. 12. The length of time required to eradicate the disease from a flock. 13. The development of an immune flock by allowing the disease to run its course. *Read at the annual meeting of the A. A. of I. and I. in P. H., Manhattan, Kansas, August, 1925.
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PROBLEMS ARISING IN THE CONTROL OP BACILLARY WHITE DIARRHEA*
250
POULTRY
SCIENCE
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We may now consider some of these points in detail. I The value of a standardized test does not need to be discussed, but just what this test should be is not at all certain at present. Various writers differ as to what should be considered a critical reaction dilution. Some believe that a 1:10 dilution should be used, while others believe that a dilution of 1:80 is low enough, others use dilutions of 1:50 etc. Many are now beginning to believe that a two dilution test is preferable. From the work here we are inclined to believe that the technique of making the test is of little importance so long as the proper dilutions are maintained, proper ingredients are used, and the utmost care exercised in conducting the test. In a study of some 6000 comparative tests we have come to the conclusion that two dilutions are necessary. We have found that dilutions of 1:20 and 1:80 are both low enough and high enough to determine most of the dangerous carriers in a flock. It has been found that a dilution of 1:10 is so low that it is difficult to read the test accurately and many birds show a borderline reaction which is difficult to interpret. A dilution of 1:80 is so high that some birds, which are in the early stages of infection, or are in such a low state of vitality as not to be able to produce sufficient agglutinins, do not react at this dilution. In a comparison of a number of tests in 1924 we found evidence of about 8% more clear reactors in the 1:20 than in the 1:80 dilutions. In 1925 there was a difference of 9% in favor of the lower dilutions. On the other hand, the higher dilution of 1:80 will determine about 0.5% reactors not determined by the loAver dilution. This is in ease of high reacting birds in which the prozone will inhibit the action in low dilutions. In birds which are tested frequently this factor would probably never be encountered. For this reason we suggest at least two dilutions of the serum. The dilutions of 1:20 and 1:80 are easily made, they will determine a large number of the infected birds and appear to be quite feasible to employ in these tests. There are certain laboratory manipulations which are very important but which we do not need to discuss here, except to mention briefly. A. The strain of organisms used in preparing the antigens. B. The medium employed in growing the antigen.
BACILLARY
WHITE
DIARRHEA
251
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C. The time of growing the antigens. D. The grade of distilled water and salt used in preparing the antigens, and in making the tests. E. The concentration of the antigen to be used. F. The method of preservation of the antigen. 6. The hydrogen-ion concentration of the antigen. H. The method of making the dilutions of serum. I. The length of time necessary for incubation çî the test. J. Temperature at which tests should be incubated. K. Interpretation of the tests. II. The proper individual who is to make the test is a question which will very soon confront the poultry breeders of this country. With the present technique the complete testing of all the birds in the country is entirely out of the question, unless each owner is prepared to do his own testing. Such a procedure will be almost useless since the average owner in many cases has not had sufficient training to make, or interpret, the tests. Until a much simpler test has been devised it should be placed only in the hands of those who are trained to some extent, at least, in laboratory manipulation. We also believe only Λvell trained in dividuals should be allowed to manufacture the antigens. Thus we may say that a simple test should be devised. III. The question of an improved field diagnosis is also of great importance. It is obviously impossible to send dead chicks to a laboratory from every flock in the country. Yet it is also impos sible at the present time to make an accurate diagnosis in the field. There are many factors which cause death in growing chicks. Nearly all chicks which die at a day or two of age have yelloΛv livers and a whitish diarrhea. Thus the problem of pro per diagnosis is of the utmost importance and we know of no simple method of diagnosis at the present time. IV. The correlation of the test with actual results obtained in the field. It is an unfortunate fact that it is not possible to obtain perfect correlation between any biological test and the re sults of field experience. Certain other factors enter which up set the predictions. We have records of one bird which would be considered a strong reactor but Which laid an average of 42 eggs per breeding season for four years, with an average fertility of 88.7%, and an average hatehability of 33.4%. On
252
POULTRY
SCIENCE
('Since this article was written the work of Hinshaw, Upp and Moore—Jour. Atn. Vet. Med. Assoc. Vol. 21, p. 631. 1926—has shown definitely that the disease may be transmitted through the air of forced draft incubators from infected to healthy chicks. They conclude in part—"That bacillary white diarrhea was disseminated by artificially infected chick-down, placed in the forced-air-draught-type of incubators," and that "chicks hatched in the compartment opposite to the one in which infected down was spread did not offer as high a percent*mortality as chicks, hatching in the infected compartments.")
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on April 6, 2015
the other hand we have had some birds which reacted no more strongly to the test but whose productivity, fertility and hatchability were almost zero. And again we have known of low reactors which have caused heavy losses, both within the shell and after hatching. We may conclude from this, that until we know more about this question the only safe mode of procedure is to eliminate all reactors froin the flock, regardless of their field performance. t V. There are undoubtedly certain factors which predispose chicks to infection by this organism. In one flock the owner had never had more than the ordinary losses, but chicks sent to neigh" boring farms from his flock suffered heavy losses. A test of this flock showed 51.6% reactors. There is no doubt but that the disease was present on this farm but the care used in brooding in one ease over that in another appeared to make the difference between success and failure in rearing these chicks. Losses in improperly brooded chicks will be much heavier when they are infected than when not infected, under similar conditions. The elimination of reactors will be of indirect if not of direct value. VI. The question of the distribution of the organisms in the incubator has not been determined, but it appears to be easily possible, especially in certain types of machines, as indicated by reports from custom hatcheries, in which eggs from diseased and disease-free flocks are hatched in the same incubators and all chicks become infected.^ VII. That the infected male is a potent cause of the dissemination of the disease is not easy to prove. In many eases in which known reacting males have been with non-reacting hens there was little evidence of a spread of the disease. Again, flocks have apparently been free from the disease until new males were introduced when trouble immediately de\'eloped. Prom the small
BACILLARY
WHITE
DIARRHEA
253
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amount of evidence which we have at hand it appears quite possible that the disease may be introduced through an infected male bird. Just how great this infection is should be determined. Of course there is no question about its being introduced through infected hens. VIII—The minimum percent of reactors which should be considered safe is zero percent. The fact must be borne in mind that we are dealing with an infectious disease, the cause, the mode of transmission, and portal of entry of which are all known. The folly of allowing any reactors to remain in the flock is shown by the following illustration. A flock was tested and all the reactors removed. Later chicks from this flock died of typical Bacillary White Diarrhea, and the organism was isolated from some of the dead chicks. A second test was made and two reactors were found. These had been introduced later without being tested. They were removed and no further trouble resulted. 8. pullora was isolated from both these birds. One of the birds was a doubtful reactor and no eggs were obtained for examination. From the stronger reactor 14 eggs and day old chicks were sent to the laboratory and 8. pullora was found in nine; These nine were from the first ten eggs obtained from this hen. This is an illustration of trouble resulting from the introduction of untested carriers into a disease-free flock. Two hundred and twenty-five chicks were lost as a result of this introduction, most of which were from the disease-free birds. It seems equally logical to say that we should quarantine all but a small percent of children with scarlet-fever, small-pox or diphtheria and still consider a school safe, as to allow a small percent of carriers of Bacillary "White Diarrhea in a flock of chickens and consider it safe. IX. The infection of adult birds from other adult birds in the same flock is very difficult to determine. Such transmission, however, is possible. We have a few records in which non-reacting hens have been with reacting males for a breeding season, but the latter did not show the reaction two years later; also a few cases in which non-reacting males have been with reacting hens without showing subsequent reaction. We have not found any cases in our experimental pens in which adult infection could be proven. While this is a probability, we have no definite proof that such transmission actually occurs. It is a possibility
254
POULTRY
SCIENCE
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that adult birds which die of the septicemic form of this disease becomes affected during adult life and die before they have a chance to develop an immunity or localize the disease. X. There should be instituted an intensive program of education as to the means by which this disease is introduced into a flock. "We have had two flocks within this territory which were considered to have been freed from the disease by testing and rigid elimination of the reactors. These flocks have both been re-infected by the introduction of non-tested stock from the outside. In one strain of birds shipped to Kansas from an eastern state we have found the disease, either in birds shipped directly, or in the off-spring of these birds, in every case tested. The original shipper vigorously denies the presence of this disease in his own flock. So long as there is general distribution of nontested stock, this disease will continue to spread throughout the country. XI. "While the question of careful sanitation is of the utmost importance it is usually neglected. The removal of reactors without being followed by proper sanitation will not remove the disease. "While we believe that sanitation is one of the most important factors in the control of this disease we shall not do more than to call it to your attention here. XII. The question is frequently asked "How long will it take to eradicate this disease from a flock?" An answer to this question will depend on many factors : 1. The birds must be carefully tested. In our opinion at least twice each year until no reactors remain. 2. The reactors must all be removed immediately, regardless of value. 3. The houses and runs must be cleaned and disinfected. The longevity of these organisms in nature, outside the body of the bird, is entirely unknown. Judging from the length of life of the typhoid and dysentery bacilli, which are somewhat like 8. pullora, they will not live very long, but this point is an uncertain one even with the former organisms. For this reason strict sanitary measures are quite necessary. 4. All birds kept on the premises must be tested. This will apply to the utility flock as well as to the breeding flock. "We feel that as long as there are any infected birds on the farm there
BAGILLARY
WHITE
DIARRHEA
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will be more or less disease carried to the breeding flock. In many cases the organisms are eliminated through the intestine. They may be carried on the boots of the workmen, by sparrows and other birds, by wind and insects, and in various other ways. If vigorous measures of testing and sanitation are followed it seems possible to develop a disease-free flock from an infected flock in three years. To our knowledge this has been accomplished in two small flocks near here. One poultryman increased the percent of fertile eggs hatched from 35.2% to 97.1% in one year by following vigorous measures of culling all reactors, followed by sanitation. These measures decreased his losses from deaths due to the disease from almost 100% to no losses for the last year. The average owner will probably not be so successful as this and it will require from three to five years to completely remove the menace of this disease from a flock. If birds are tested and all reactors removed twice a year, three years should be suSicient for complete eradication. X I I I . Some owners of valuable flocks may hope to build up a disease-free flock of immune birds by allowing nature to take her course and thus eliminating the unfit. This is possible but not probable. The human race has suffered from tuberculosis for several thousand years, and while certain races are quite resistant to the disease, there is no race which is absolutely immune. We must also keep in mind the fact that we know very little about immunity. Today we do not know why certain individuals become naturally or artificially immune to typhoid-fever while others do not. We do know, however, that certain individuals never become immune to this disease regardless of treatment. We should not expect 100% result of any kind while dealing with living organisms. In conclusion we wish to call attention again to the facts : 1. That Bacillary White Diarrhea is an infectious disease; 2. That it causes much greater losses than are generally recognized ; 3. That it may be eradicated from a flock by vigorous measures ; 4. That it cannot be controlled until poultry breeders realize the fact that a " c a r r i e r " may be entirely harmless on one day and lay an infected egg another day ;
256
POULTRY
SCIENCE
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5. That the agglutination test is the only reliable means which we have at present for the detection of carriers ; and 6. That it will be impossible to eradicate this disease unless breeders are willing to eliminate all carriers from the flock regardless of their value. A more concerted effort is necessary on the part of all who come in contact with this disease. A few of the problems have been discussed in this paper, but there are many more which concern the producer, the hatcheryman and the laboratory worker. Without the co-operation of all these groups poultry will continue to suffer severe losses from this disease.
AUGUST-SEPTEMBER
No. 6
BY L . D . B U S H N E L L AND W . R . H I N S H A W
Department of Bacteriology Kansas State Agriculture Experiment Station This is a subject which has become more a n d more i m p o r t a n t with the increase in p o u l t r y population in the country a n d with the r a p i d transfer of p o u l t r y breeding stock from one locality to another. The problem m a y be considered from three angles—that of the laboratory worker, t h a t of the practical p o u l t r y producer a n d t h a t of the commercial hatcheryman. The relationship between the three groups must be close, otherwise no actual progress can be expected in the eradication of this disease. Below are enumerated some of the facts which should be brought u n d e r very careful study. 1. A standardization of the test. 2. The proper individual who is to make the test. 3. The development of an improved method of field diagnosis. 4. A correlation of the test with carefully controlled field results. 5. Factors predisposing to infection. 6. Influence of the incubator upon the spread of the infectious material. 7. A study of the rôle of the infected male, in the dissemination of the disease. 8. The minimum percentage of reactors which may be considered safe. 9. The amount of infection contracted by adults and the influence on dissemination of the disease. 10. Modes of introduction of the disease from the outside. 11. Methods of sanitation necessary for the control of the disease. 12. The length of time required to eradicate the disease from a flock. 13. The development of an immune flock by allowing the disease to run its course. *Read at the annual meeting of the A. A. of I. and I. in P. H., Manhattan, Kansas, August, 1925.
249
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PROBLEMS ARISING IN THE CONTROL OP BACILLARY WHITE DIARRHEA*
250
POULTRY
SCIENCE
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on April 6, 2015
We may now consider some of these points in detail. I The value of a standardized test does not need to be discussed, but just what this test should be is not at all certain at present. Various writers differ as to what should be considered a critical reaction dilution. Some believe that a 1:10 dilution should be used, while others believe that a dilution of 1:80 is low enough, others use dilutions of 1:50 etc. Many are now beginning to believe that a two dilution test is preferable. From the work here we are inclined to believe that the technique of making the test is of little importance so long as the proper dilutions are maintained, proper ingredients are used, and the utmost care exercised in conducting the test. In a study of some 6000 comparative tests we have come to the conclusion that two dilutions are necessary. We have found that dilutions of 1:20 and 1:80 are both low enough and high enough to determine most of the dangerous carriers in a flock. It has been found that a dilution of 1:10 is so low that it is difficult to read the test accurately and many birds show a borderline reaction which is difficult to interpret. A dilution of 1:80 is so high that some birds, which are in the early stages of infection, or are in such a low state of vitality as not to be able to produce sufficient agglutinins, do not react at this dilution. In a comparison of a number of tests in 1924 we found evidence of about 8% more clear reactors in the 1:20 than in the 1:80 dilutions. In 1925 there was a difference of 9% in favor of the lower dilutions. On the other hand, the higher dilution of 1:80 will determine about 0.5% reactors not determined by the loAver dilution. This is in ease of high reacting birds in which the prozone will inhibit the action in low dilutions. In birds which are tested frequently this factor would probably never be encountered. For this reason we suggest at least two dilutions of the serum. The dilutions of 1:20 and 1:80 are easily made, they will determine a large number of the infected birds and appear to be quite feasible to employ in these tests. There are certain laboratory manipulations which are very important but which we do not need to discuss here, except to mention briefly. A. The strain of organisms used in preparing the antigens. B. The medium employed in growing the antigen.
BACILLARY
WHITE
DIARRHEA
251
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on April 6, 2015
C. The time of growing the antigens. D. The grade of distilled water and salt used in preparing the antigens, and in making the tests. E. The concentration of the antigen to be used. F. The method of preservation of the antigen. 6. The hydrogen-ion concentration of the antigen. H. The method of making the dilutions of serum. I. The length of time necessary for incubation çî the test. J. Temperature at which tests should be incubated. K. Interpretation of the tests. II. The proper individual who is to make the test is a question which will very soon confront the poultry breeders of this country. With the present technique the complete testing of all the birds in the country is entirely out of the question, unless each owner is prepared to do his own testing. Such a procedure will be almost useless since the average owner in many cases has not had sufficient training to make, or interpret, the tests. Until a much simpler test has been devised it should be placed only in the hands of those who are trained to some extent, at least, in laboratory manipulation. We also believe only Λvell trained in dividuals should be allowed to manufacture the antigens. Thus we may say that a simple test should be devised. III. The question of an improved field diagnosis is also of great importance. It is obviously impossible to send dead chicks to a laboratory from every flock in the country. Yet it is also impos sible at the present time to make an accurate diagnosis in the field. There are many factors which cause death in growing chicks. Nearly all chicks which die at a day or two of age have yelloΛv livers and a whitish diarrhea. Thus the problem of pro per diagnosis is of the utmost importance and we know of no simple method of diagnosis at the present time. IV. The correlation of the test with actual results obtained in the field. It is an unfortunate fact that it is not possible to obtain perfect correlation between any biological test and the re sults of field experience. Certain other factors enter which up set the predictions. We have records of one bird which would be considered a strong reactor but Which laid an average of 42 eggs per breeding season for four years, with an average fertility of 88.7%, and an average hatehability of 33.4%. On
252
POULTRY
SCIENCE
('Since this article was written the work of Hinshaw, Upp and Moore—Jour. Atn. Vet. Med. Assoc. Vol. 21, p. 631. 1926—has shown definitely that the disease may be transmitted through the air of forced draft incubators from infected to healthy chicks. They conclude in part—"That bacillary white diarrhea was disseminated by artificially infected chick-down, placed in the forced-air-draught-type of incubators," and that "chicks hatched in the compartment opposite to the one in which infected down was spread did not offer as high a percent*mortality as chicks, hatching in the infected compartments.")
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on April 6, 2015
the other hand we have had some birds which reacted no more strongly to the test but whose productivity, fertility and hatchability were almost zero. And again we have known of low reactors which have caused heavy losses, both within the shell and after hatching. We may conclude from this, that until we know more about this question the only safe mode of procedure is to eliminate all reactors froin the flock, regardless of their field performance. t V. There are undoubtedly certain factors which predispose chicks to infection by this organism. In one flock the owner had never had more than the ordinary losses, but chicks sent to neigh" boring farms from his flock suffered heavy losses. A test of this flock showed 51.6% reactors. There is no doubt but that the disease was present on this farm but the care used in brooding in one ease over that in another appeared to make the difference between success and failure in rearing these chicks. Losses in improperly brooded chicks will be much heavier when they are infected than when not infected, under similar conditions. The elimination of reactors will be of indirect if not of direct value. VI. The question of the distribution of the organisms in the incubator has not been determined, but it appears to be easily possible, especially in certain types of machines, as indicated by reports from custom hatcheries, in which eggs from diseased and disease-free flocks are hatched in the same incubators and all chicks become infected.^ VII. That the infected male is a potent cause of the dissemination of the disease is not easy to prove. In many eases in which known reacting males have been with non-reacting hens there was little evidence of a spread of the disease. Again, flocks have apparently been free from the disease until new males were introduced when trouble immediately de\'eloped. Prom the small
BACILLARY
WHITE
DIARRHEA
253
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on April 6, 2015
amount of evidence which we have at hand it appears quite possible that the disease may be introduced through an infected male bird. Just how great this infection is should be determined. Of course there is no question about its being introduced through infected hens. VIII—The minimum percent of reactors which should be considered safe is zero percent. The fact must be borne in mind that we are dealing with an infectious disease, the cause, the mode of transmission, and portal of entry of which are all known. The folly of allowing any reactors to remain in the flock is shown by the following illustration. A flock was tested and all the reactors removed. Later chicks from this flock died of typical Bacillary White Diarrhea, and the organism was isolated from some of the dead chicks. A second test was made and two reactors were found. These had been introduced later without being tested. They were removed and no further trouble resulted. 8. pullora was isolated from both these birds. One of the birds was a doubtful reactor and no eggs were obtained for examination. From the stronger reactor 14 eggs and day old chicks were sent to the laboratory and 8. pullora was found in nine; These nine were from the first ten eggs obtained from this hen. This is an illustration of trouble resulting from the introduction of untested carriers into a disease-free flock. Two hundred and twenty-five chicks were lost as a result of this introduction, most of which were from the disease-free birds. It seems equally logical to say that we should quarantine all but a small percent of children with scarlet-fever, small-pox or diphtheria and still consider a school safe, as to allow a small percent of carriers of Bacillary "White Diarrhea in a flock of chickens and consider it safe. IX. The infection of adult birds from other adult birds in the same flock is very difficult to determine. Such transmission, however, is possible. We have a few records in which non-reacting hens have been with reacting males for a breeding season, but the latter did not show the reaction two years later; also a few cases in which non-reacting males have been with reacting hens without showing subsequent reaction. We have not found any cases in our experimental pens in which adult infection could be proven. While this is a probability, we have no definite proof that such transmission actually occurs. It is a possibility
254
POULTRY
SCIENCE
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on April 6, 2015
that adult birds which die of the septicemic form of this disease becomes affected during adult life and die before they have a chance to develop an immunity or localize the disease. X. There should be instituted an intensive program of education as to the means by which this disease is introduced into a flock. "We have had two flocks within this territory which were considered to have been freed from the disease by testing and rigid elimination of the reactors. These flocks have both been re-infected by the introduction of non-tested stock from the outside. In one strain of birds shipped to Kansas from an eastern state we have found the disease, either in birds shipped directly, or in the off-spring of these birds, in every case tested. The original shipper vigorously denies the presence of this disease in his own flock. So long as there is general distribution of nontested stock, this disease will continue to spread throughout the country. XI. "While the question of careful sanitation is of the utmost importance it is usually neglected. The removal of reactors without being followed by proper sanitation will not remove the disease. "While we believe that sanitation is one of the most important factors in the control of this disease we shall not do more than to call it to your attention here. XII. The question is frequently asked "How long will it take to eradicate this disease from a flock?" An answer to this question will depend on many factors : 1. The birds must be carefully tested. In our opinion at least twice each year until no reactors remain. 2. The reactors must all be removed immediately, regardless of value. 3. The houses and runs must be cleaned and disinfected. The longevity of these organisms in nature, outside the body of the bird, is entirely unknown. Judging from the length of life of the typhoid and dysentery bacilli, which are somewhat like 8. pullora, they will not live very long, but this point is an uncertain one even with the former organisms. For this reason strict sanitary measures are quite necessary. 4. All birds kept on the premises must be tested. This will apply to the utility flock as well as to the breeding flock. "We feel that as long as there are any infected birds on the farm there
BAGILLARY
WHITE
DIARRHEA
255
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on April 6, 2015
will be more or less disease carried to the breeding flock. In many cases the organisms are eliminated through the intestine. They may be carried on the boots of the workmen, by sparrows and other birds, by wind and insects, and in various other ways. If vigorous measures of testing and sanitation are followed it seems possible to develop a disease-free flock from an infected flock in three years. To our knowledge this has been accomplished in two small flocks near here. One poultryman increased the percent of fertile eggs hatched from 35.2% to 97.1% in one year by following vigorous measures of culling all reactors, followed by sanitation. These measures decreased his losses from deaths due to the disease from almost 100% to no losses for the last year. The average owner will probably not be so successful as this and it will require from three to five years to completely remove the menace of this disease from a flock. If birds are tested and all reactors removed twice a year, three years should be suSicient for complete eradication. X I I I . Some owners of valuable flocks may hope to build up a disease-free flock of immune birds by allowing nature to take her course and thus eliminating the unfit. This is possible but not probable. The human race has suffered from tuberculosis for several thousand years, and while certain races are quite resistant to the disease, there is no race which is absolutely immune. We must also keep in mind the fact that we know very little about immunity. Today we do not know why certain individuals become naturally or artificially immune to typhoid-fever while others do not. We do know, however, that certain individuals never become immune to this disease regardless of treatment. We should not expect 100% result of any kind while dealing with living organisms. In conclusion we wish to call attention again to the facts : 1. That Bacillary White Diarrhea is an infectious disease; 2. That it causes much greater losses than are generally recognized ; 3. That it may be eradicated from a flock by vigorous measures ; 4. That it cannot be controlled until poultry breeders realize the fact that a " c a r r i e r " may be entirely harmless on one day and lay an infected egg another day ;
256
POULTRY
SCIENCE
Downloaded from http://ps.oxfordjournals.org/ at Library, University of Guelph on April 6, 2015
5. That the agglutination test is the only reliable means which we have at present for the detection of carriers ; and 6. That it will be impossible to eradicate this disease unless breeders are willing to eliminate all carriers from the flock regardless of their value. A more concerted effort is necessary on the part of all who come in contact with this disease. A few of the problems have been discussed in this paper, but there are many more which concern the producer, the hatcheryman and the laboratory worker. Without the co-operation of all these groups poultry will continue to suffer severe losses from this disease.