240 Diseases of Poultry 



birds cannot see to eat. They get poor and die from exhaus- 

 tion. When the mucous membrane of the mouth develops 

 diphtheritic membranes, death occurs earher than in other 

 forms. 



Etiology. — The lesions of this disease resemble the lesions 

 of roup and many of the same micro-organisms are found in 

 the two cases. The organisms isolated from the lesions of 

 sore-head include several bacteria, a coccidium, a yeast and 

 several molds. The coccidium, one of the molds, and one 

 of the bacteria have each been considered the cause of the 

 disease by different workers. The real cause of the disease 

 and its relation to roup must be determined by further 

 investigations. 



Many recent investigations have indicated that the disease 

 is caused by a filterable virus.^ In regard to the etiology 

 and mode of transmission Gary ^ says : 



" It is evidently infectious ; because the disease in all its 

 forms, spreads rather rapidly from one chicken or pigeon to 

 another. Ward, Harrison and others have transmitted, in 

 some cases quite readily by carrying a small amount of dis- 

 eased material (exudate and blood), from a sore-head chicken 

 to healthy chickens. It is also quite certain that chicken pox 

 and pigeon pox are identical or one and the same disease. 



"Mosquitoes, gnat flies, chicken mites (ticks), chicken lice, 

 chicken foot mites {Sarcoptes mutans) and possibly cock- 

 roaches may sometimes be carriers of the real virus. It seems 

 quite certain that mosquitoes can transmit the virus from 



' For example see : 



Bruet, E., "Contribution a I'etude I'epithglioma contagieux des 

 Olseaux." Ann. I'Inst. Past., T. 29, pp. 742-765, 1906. 



Sweet, C. D., "A Study of Epithelioma Contagiosum of the 

 Common Fowl." Univ. of Calif. Public Zool., Vol. II, pp. 29-51, 

 1913. 



* Gary, C. A., "Chicken-pox or Sore-head in Poultry." Alabama 

 Agr. Expt. Stat. Bui. 136, pp. 17-56, 1906. 



