CHAPTER XXVI 



HEMOERHAGIC SEPTICEMIAS AND PLAGUE— THE GENUS 

 PASTEUKELLA 



The genus Pasteurella includes all of these bacteria which 

 are aerobic, nonmotile, Gram-negative rods, not producing 

 spores which show -usually a decided tendency toward polar 

 staining and possess a comparatively slight power of fer- 

 mentation. The organisms belonging to this genus are 

 closely related to certain forms of the genus Bacterium and 

 in some cases it is quite difficult to differentiate between the 

 two genera. The first organism described belonging to this 

 group was that of chicken cholera, studied by Pasteur. 

 Other organisms closely related were found later and 

 Lignieres created the genus Pasteurella to include them all. 

 The term pasteurellosis is a designation of the disease caused 

 by any member of this group. 



Bacteria of this group have been found associated with 

 a great variety of diseases in animals and in man. The most 

 important are the Jiemorrhagic septicemia of cattle and of 

 sheep ; the septic pleuropneumonia of calves ; fowl cholera; 

 swine septicemia and swine plague, and iubonic plague in 

 man. The organisms causing these diseases in various ani- 

 mals are so closely related and so difficult if not impossible 

 to differentiate in the laboratory, that some authors have 

 regarded all as belonging to a single species and have 

 designated as varieties merely those forms of causing dis- 

 eases in the various animals. 



In the present discussion the hemorrhagic septicemia of 

 birds caused by Pasteurella cholerce-gallinarum, of cattle 

 caused by Pasteurella ioviseptica, of swine caused by Pas- 



345 



