PREVENTIVE MEDICINE 333 



since been seen in Germany and other parts of Europe. It possibly 

 occurs in Great Britain, but absolute proof is wanting. The fowl 

 is most commonly attacked, and the disease does not show a great 

 tendency to spread amongst other birds, these often escaping though 

 exposed to infection. Experimentally, the disease can be trans- 

 mitted with difficulty by inoculation and by ingestion to other 

 poultry. Freese* failed to infect old and young ducks and old geese. 

 The pigeon enjoys a high degree of immunity and the domesticated 

 mammals are not susceptible. Freese has described outbreaks 

 among geese in Germany, and has recorded the fact that sparrows 

 may become infected by contact with fowls suffering from the 

 disease. Birds become infected by the ingestion of faeces, which 

 always contains the virus and which is the chief agent in the spread 

 of the disease. The important discovery by Freese that sparrows 

 may become infected indicates one method by which outbreaks may 

 be originated. The period of incubation is 3 to 5 days in natural 

 cases, and the disease often runs its course in 2 to 4 days or it may be 

 longer. 



The mortality is high and few cases recover. According to 

 Leclainchef the virus does not live long in soil or water but is relat- 

 ively insensitive to desiccation, dried blood remaining infective for 

 20 to 25 days. The virus is more easily destroyed by disinfectants, 

 but is very resistant to glycerine. Maggiora and Valenti$ found 

 that blood hermetically sealed in pipettes and kept in a cool, dark 

 place retained its virulence for at least 45 days. Exposed to air 

 and diffuse sunlight the virus remained active for 15 days, and on 

 a hot summer day virulence was lost in 40 hours. The virus in 

 blood is destroyed by 5 minutes' exposure at 65 C. 



AVIAN DIPHTHERIA (diphtheritic roup) is a specific disease of 

 birds characterised by the production of false membranes on the 

 throat and nasal passages. Some have held that avian and human 

 diphtheria are one and the same disease, and have cited instances 

 in which it was alleged that birds had originated outbreaks of 

 diphtheria in the human subject. In some instances examination 

 of the evidence has shown no valid grounds for the assertion, and 

 in other instances the evidence was at least doubtful. The disease 

 has also been held to be a form of epithelioma contagiosum of birds 

 (Hutyra and Marek). The truth of these assertions also seems 

 to be very doubtful and, at the present time, it can be laid down 



*Journ. Comp. Path., 1918, Vol. XXL, p. 212, Trans. 



t/ourn. Comp. Path., 1904, Vol. XVII., p. 83, Abs. 



Uourn. Comp. Path., 1918, Vol. XXL, p. 169, Ref. 



Hutyra and Marek, Spec. Path., Vol. I., p. 424, Trans. 



