334 VETERINARY HYGIENE 



as nearly certain that avian diphtheria is a distinct and definite 

 morbid entity. 



The cause is not known with certainty, though according to the 

 researches of Bordet and Fally* it is an extremely small organism, 

 which is always present in the false membranes and which produces 

 hardly perceptible growths on special culture media. Others (Guerin, 

 Nocard) considered the cause to be a pasteurella. The disease is 

 conveyed by inoculation and by ingestion, but infection does not 

 easily occur and long contact with virulent material is necessary. 

 It usually lasts from 2 to 3 weeks ; recovery is sometimes complete 

 and occasionally relapses occur. Friedbergerf places the mortality 

 at 50 to 70 per cent, and much higher in young birds. 



EPITHELIOMA CONTAGIOSUM (avian variola, fowl pox). A 

 contagious disease of poultry characterised by the occurrence of 

 wart-like eruptions on the unfeathered portions of the body and 

 particularly on the comb, wattles and eyelids. Outbreaks occur 

 among fowls, pigeons, turkeys, geese, &c. Marx and StickerJ. 

 showed in 1902 that the virus of the disease will pass through a 

 bacterial filter. According to the later researches of Borrel, Burnet 

 and others it seems to be rather uncertain whether the disease 

 should be classed among those due to ultravisible viruses. Accord- 

 ing to Burnet the cause, which can be readily shown by inoculation 

 to be present in the lesions, is at least as large as the organism 

 of bovine pleuro-pneumonia and can be detected microscopically. 

 At the same time it has frequently been found to pass through the 

 more open-grained bacterial filters. Natural infection may occur 

 either by contact or by ingestion of scales which drop off diseased 

 birds. Experimentally the disease can be conveyed by inoculation 

 or by feeding. Marx and Sticker|| have shown that the virus is 

 very resistant, thus material from the lesions was infective after 

 being heated to 60 C for 3 hours. A crust containing the virus 

 was infective after exposure for 2 months to desiccation and light 

 and, at times, to direct sunlight. The virus was destroyed in half 

 an hour by 2 per cent, carbolic acid, but not by 1 per cent. The 

 nodules in glycerine are infective after 30 days. The disease appar- 

 ently becomes adapted to one species of bird, the transmission from 

 one species to another is not always easy. The period of incubation 

 is 5 to 6 days. The disease is not usually fatal, the warty lesions 



*Ann. Inst. Past., Vol. XXIV., p. 563. 

 t Hutyra and Marek, Spec. Path., Vol. I., p. 434. 

 $ Journ. Comp. Path., 1918, Vol. XXL, p. 171, Ref. 

 Journ. Comp. Path., 1918, Vol. XXI., p. 173, Ref. 

 II Journ. Comp. Path., 1918, Vol. XXL, p. 172, Ref. 



