CHAPTER IV 



The Behavior of the Bacteriophage in Epidemics 



1. AVIAN TYPHOSIS 



In the preceding chapter we have dealt with the behavior of the 

 bacteriophage protobe within the intestinal tract of animals having the 

 disease avian typhosis. Let us now see what happens in those animals 

 which live in regions where this disease is prevalent but which resist 

 infection. 



Let us consider first a fact bearing on the territory involved in the 

 epizootic. During the period involved in this study eighty-one 

 examinations were made upon the feces of barn-yard animals, not only in 

 France but also in Indo-China, in regions where avian typhosis had not 

 occurred in epidemic form among the fowls for several years. In each 

 of these examinations a bacteriophage active for one or several of the 

 bacilli of the colon-typhoid-dysentery group was isolated, but in no 

 instance has the bacteriophage shown any detectable activity for B. 

 gallinarum. 



In contaminated regions the situation is quite different. As an 

 example, observations made on a farm located at Pougy-sur-Aube may 

 be cited, where the disease was followed very closely. The disease 

 appeared in 1917 in July. Within the period of a month fifty-one of 

 the ninety-eight fowls died; then the epizootic disappeared. In May, 

 1918, it reappeared in less violent form. Twenty-five of one hundred 

 and four fowls died in the period from May to September, and it again 

 disappeared. In 1919 it broke out again early in April. On the 21st 

 of May, twenty-one of eighty had died. At this time I beganmy obser- 

 vations. 



On May 21, specimens of the excrement of thirty of the fifty-nine 

 survivors were taken. Examination made later in the laboratory, 

 showed in twenty-six a bacteriophage of weak or moderate activity for 

 B. gallinarum (23 were +, 3 were + + ), in four it was absent. On May 

 22, two chickens contracted the disease. The specimens taken the day 

 before were numbered and examination showed that an active bacterio- 

 phage had not been found in these two animals. On May 23 one of the 

 two chickens affected the day before died. On May 24, a third chicken, 

 sick in the morning, died in the following night. Its excrement, col- 



