ERADICATION OF PULLORUM DISEASE 1931-32 23 



during a period of 12 months. The birds were maintained in small houses which 

 were cleaned out at long intervals so as to allow every opportunity of infection 

 taking place. Edwards and Hull (30") observed that the disease may spread from 

 infected to non-infected hens without the presence of male birds. Monthly 

 agglutination tests extending over a period of a year revealed reactors at the 

 third, seventh, eighth, and tenth months. Brunett (13, 14) found that the 

 disease was not transmitted from infected to non-infected hens during a period 

 of 7 months' contact. After the addition of 3 non-reacting mature male birds, 

 a number of non-reacting hens became reactors. Later he observed that among 

 13 reacting birds and 12 non-reacting birds with 2 non-reacting males, no evidence 

 of transmission of the infection was obtained for a period of 9 months. However, 

 among 14 reactors and 14 non-reactors without males being present, the infec- 

 tion was found to have spread to 1 bird during a period of 9 months. Beach and 

 Michael (3) reported that among 37 non-reacting hens kept in a pen with 61 

 reacting hens for 19 months, 12 became reactors. Kernkamp (55) found that 

 11 of 24 negative hens developed positive agglutination reactions while in con- 

 tact with infected birds for a period of approximately 13 months. In another 

 experiment, 8 of 17 negative hens became positive while in contact with infected 

 birds for 9 months. S. pullorum was isolated from 24 per cent of the birds that 

 were non-reacting at the beginning of the contact period. Warrack and DaUing 

 (941 observed in an experiment of 18 weeks' duration that transmission of pul- 

 lorum disease occurred among adult stock between reactors and non-reactors. 

 Furthermore, the smaller the space in which fowls are confined, the greater is 

 the chance of such transmission taking place. 



The presence of the organism in the intestinal and reproductive tracts of 

 infected adult birds has been observed. Kerr (56) isolated S. pullorum from the 

 feces of adult birds. Miessner (65) reported that Ansorg and others observed 

 the presence of S. pullorum in the cloacae of hens. Lesbouyries (58) stated that 

 it is probable that adult birds become infected through contaminated droppings, 

 in places where trap nests are not employed, by feed containing a debris of shells, 

 and through feed contaminated with 5. pullorum. 



Known non-infected birds may contract the disease by eating fresh or incu- 

 bated eggs laid by infected hens. Rettger and Stoneburn (72, 74) isolated S. 

 pullorum from incubated infertile and fertile eggs. The organism was also 

 recovered from fresh eggs. Jones (52, 53) was successful in isolating the organism 

 from fresh eggs laid by fowls that had overcome the disease during chicldiood. 

 He also observed an outbreak of the disease in an acute form in adult fowls caused 

 by the feeding of incubated eggs that contained S. pullorum. Mathews (63) 

 observed an outbreak of infection in a flock as a result of feeding incubated, 

 infertile eggs. He succeeded in bringing about infection in pullets by feeding 

 incubated eggs laid by infected hens. Van Heelsbergen (91) reported that an 

 important channel of pidlorum disease dissemination is through so-called "egg- 

 picking." In another part of this bulletin an investigation is reported which 

 shows that non-infected females may contract pullorum disease through eating 

 fresh eggs laid by infected hens. 



Experimental findings concerning transmission of the disease among sexually 

 immature pullets have not been found in our review of the Uterature. Pullets 

 that had not attained egg production were regarded as sexually immature. 

 Since a knowledge relating to the dissemination of the infection during this age 

 might be of value in the control and eradication of the disease, the following 

 problem was regarded worthy of investigation. 



Can sexually immature pullets infected with S. pullorum transmit the infec- 

 tive agent to non-infected pullets when both groups are maintained in close 

 contact? 



