LUNG PLAGUE OF CATTLE 409 



to extract the loose teeth, scrape away the necrosed tissue and 

 apply iodin tincture to the raw areas remaining. If per- 

 sisted in, healing can be produced usually in ten days. 



LUNG PLAGUE OF CATTLE. CONTAGIOUS PLEURO- 

 PNEUMONIA OF CATTLE. 



Definition. — ^Lung plague of the ox is a specific contagio- 

 infectious pleuropneumonia which may assume an acute, 

 subacute or chronic form and is due to a filtrable although 

 visible virus. 



Occurrence. — ^The disease does not exist in the United States 

 at the present time. In 1843 an outbreak occiu'red in New 

 York, which had its origin in an infected cow imported from 

 England. In the years following the disease spread through- 

 out the country, getting as far west as the Mississippi River 

 and south to Virginia. It was not until 1892 that it was 

 finally entirely stamped out. 



Lung plague is now well under control in Europe, although 

 still quite prevalent in Spain. Throughout Asia and Africa 

 the disease is general. Australia, New Zealand and Tasmania 

 are infected. In the Philippine Islands the disease is wide- 

 spread. 



Etiology. — ^Lung plague is due to a very minute micro- 

 organism which passes through coarse porcelain filters but 

 may be seen under the microscope when magnified over 1500 

 diameters. It is the smallest visible microorganism as yet 

 known, being almost ultramicroscopic. The organism has 

 been grown in artificial media. The virus is found in the 

 pleural exudate, diseased lung and in nasal discharge. The 

 blood rarely is infectious. 



Natural Infection. — ^Probably through the respiratory tract. 

 Experiments to produce typical lung plague in susceptible 

 animals by inhalation or feeding have not been successful. 

 The disease spreads usually by direct contact with infected 

 animals. Infected and emptied stables in which within a 

 year sick cattle had been kept ai'e common sources of infec- 

 tion. Where cattle are crowded together in a barn the dis- 

 ease spreads most rapidly. On the other hand, however, a 



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