INFECTIOUS LARYNGOTRACHEITIS CARRIERS 165 



into the feed in both cages, clawing it over and picking out pieces to nibble. 

 Since the susceptible chickens showed no signs of the disease, the mice and 

 sparrows did not serve as mechanical carriers under these conditions. 



Ten pigeons from two widely separated flocks were inoculated intratracheally 

 with a virulent strain of the California infectious laryngotracheitis virus. The 

 pigeons were not affected by the disease, although two pullets inoculated with 

 the same virus at the same time died in five days. The virus lived only a few 

 hours in the tracheas of the pigeons, for after one day tracheal exudates from 

 them did not infect susceptible chickens. Beach (1931) was imable to reproduce 

 the disease by inoculation in pigeons. 



A goose sent to the diagnostic service, apparently suffering from infectious 

 laryngotracheitis, was killed and necropsied. The gross and histopathological 

 lesions indicated infectious laryngotracheitis, but four chickens inoculated intra- 

 tracheally with fresh tracheal exudate failed to develop the disease, although 

 they readily succumbed to a natural infection later. Graham and Thorp (1931) 

 have reported a similar experience with a wild goose. As yet it is uncertain 

 whether or not geese are susceptible to the disease or act as carriers of the virus. 



An attempt was made to determine whether man could serve as a mechanical 

 carrier of infectious laryngotracheitis. In this experiment 24 susceptible pullets 

 and cockerels were placed in separate cages. The cages were set on three double- 

 deck stands well isolated from one another. The birds on the first stand were 

 numbered Al, A2, A3, A4, A5, A6, A7, and A8, respectively; those on the second 

 stand, Bl, B2, etc.; and those on the third stand, CI, C2, etc. Al and Bl were 

 inoculated intratracheally with a virulent strain of infectious laryngotracheitis, 

 while CI was kept as an uninoculated control. Six days after inoculation both 

 .\1 and Bl showed symptoms of infectious laryngotracheitis and were emitting 

 trachea! exudate tinged with blood during paro.xysms of coughing. Apparently 

 the conditions were right for the next step in the experiment. Accordingly, the 

 experimenter carefully washed his hands and arms in warm, 2 per cent compound 

 cresol solution, hnally rinsing in running tap water, and drying with paper towels. 

 He then put on a recently laundered laboratory coat and handled the pullets and 

 cockerels in the A cages as in a poultry judging contest, beginning with Al and 

 taking each bird consecutively. After disinfecting hands and arms and changing 

 to another laboratory coat, he handled the birds in the B cages just as he had 

 those in the A cages. The same procedure was repeated for the birds in the last 

 group, begiiming with CI. All of the pullets and cockerels in the A cages, five 

 in the B cages, and none in the C cages came down with infectious laryngotra- 

 cheitis within the period of incubation for this disease, indicating that man may 

 serve as a mechanical carrier of the virus when the excretions are fresh and 

 carried directly from sick to healthy susceptible birds. Later the controls (C 

 birds) and B5, B7, and B8, which did not take the disease by handling, were 

 inoculated intratracheally Avith virulent tracheal exudate from A2 and A3. B8 

 and all of the controls came down with infectious laryngotracheitis in due season 

 and died. B5 and B7 did not contract the di.sease, and were later found to be 

 resistant to it. 



Acute Cases 



The most important distributor in infectious laryngotracheitis, as in most 

 acute infectious diseases, is the recently infected individual. The virus is nearly 

 always found in the tracheal exudate during the acute stages, and it has been 

 demonstrated in the internal organs in a limited number of cases in which an 

 especially virulent virus was used and special laboratory methods employed. 



