INFECTIOUS LARYNGOTRACHEITIS CARRIERS 



By Charles S. (Jibbs, 

 Research Professor of \'eterinary Science 



Chronic carriers of tlie virus of infectious laryngotracheitisl were suspected a< 

 the beginning of this study, because cleaning and disinfecting the houses and 

 moving apparently recovered birds to new quarters had failed to control the 

 disease in more instances than could be accovmted for by accidental infection. 

 Moreover, on several poultry farms, the annual appearance of the disease among 

 pullets and cockerels brought in from the range in the fall and mixed with older 

 birds strongly indicated the presence of carriers among the adult birds. Then, 

 in an examination of 144 birds by means of intratracheal swabs, two convalescent 

 birds were observed (Gibbs, 1931) eliminating virus longer than usual while show- 

 ing no symptoms of disease. Although these observations did not actually 

 reveal the existence of chronic carriers, they signified the possibility of such, and 

 the investigation was continued until the 14 chronic carriers described in this 

 bulletin were found and studied. 



Since these experiments on carriers of infectious laryngotracheitis were 

 completed, Komarov and Beaudette (1931) report the finding of chronic carriers 

 by the same method. While these investigators did not state the total number 

 of birds examined, they concluded: "P'inally, in a population of 25 birds which 

 had infectious bronchitis 16 months previously, 3 carriers of the virus were 

 determined." 



For some time chronic carriers of infectious laryngotracheitis have been 

 suspected. Now experimental evidence from two independent sources shows 

 that such carriers actually exist. 



Experiments on subjects closely related to chronic carriers, such as mechan- 

 ical carriers, the channel of infection, the viability of the virus imder natural 

 conditions, and practical suggestions for the control of the disease are included 

 in this bulletin. 



Mechanical Carriers 



Experiments have been conducted with sparrows and mice as possible carriers 

 of infectious laryngotracheitis. Thus far the results indicate that these pests 

 are not important in the transn)ission of the virus, as neither of them is suscepti- 

 ble to the disease. However, both sparrows and mice .served as mechanical carriers 

 when (he feathers and hairs were smeared with fresh exudate from the tracheas 

 of birds dying of acute infectious laryngotracheitis, a condition not likely to occur 

 under natural circumstances. In another experiment two cages, one containing 

 diseased birds, the other healthy birds, were placed twenty inches apart and 

 connected with a wire runway, arranged so that only the sparrows and mice 

 could pass from cage to cage, as shown in Figure 1. During the day the spar- 

 rows were seen passing hack and forth in search of feed. At night the mice got 



1 This name was .^uggestprl by Dr. H. J. Htafseth, at the 1929 Confoionco of State and Fod- 

 cral Research Worker-s in Animal Diseases; and it has heen reoorninended by the Special Com- 

 mittee on Poultry Diseases appointed to report at the 19.31 meeting of the .\merican Veterinary 

 Medical Association. In order to assist the movement for standardized nomenclature in poultry 

 disea.ses, the name infectious laryngotracheitis is, therefore, used in this bulletin for infectious 

 trachitis and infectious bronchitis. 



