9i8 



THE ANIMAL CARRIERS OF DISEASES 



They therefore behave more like the bacteria than like animal 

 parasites in the carrier. 



For our present purpose relapsing fevers may be divided into 

 two groups as follows: — 



I. The Louse Group, which is characterized by being carried by 

 the louse. These are the European, the North African, the Indian, 

 and the American types. 



From the infective blood the spirochsetes pass into the alimentary 

 canal of the louse, and from thence into its coelom, where they 

 remain, and from there they find their way into the eggs, which are 

 infective, as are their larvae. 



Infection of man is brought about by contaminative means — i.e., 

 the louse in biting causes irritation, the man scratches his skin, 

 causing abrasions, and at the same time kills a louse, crushes it, 

 and rubs it into the abrasions, which become infected. Nicolle 

 and Blaizot believe that the organisms which are infective are 

 granules just before they reappear as spirochaetes. Sergent and 

 Foley have stated that there were very small virulent forms in man 

 during apyrexia. 



In this life-cycle there is no definitive host, merely two hosts 

 of equal value. Only the insect is the preservative host and the verte- 

 brate the intermediary host. 



I. The Louse Group of Relapsing Fevers. 



Parasites. 



Preservative 

 Host. 



Preservative 

 Reservoir. 



Infection. 



Inter- 

 mediate 

 Host. 



Trans- 

 mission. 



S. recurrentis, 

 S. herhera, 

 S. carteri, 

 S. novyi. 



Pediculus 

 corporis. 



Lice by 

 hereditary 

 transmission. 



Small forms in 

 body cavity. 



Co ntaminative . 



Man. 



Small 

 blood 

 forms. 



Ingestive. 



Spirochaital Epidemic Jaundice. — This is caused by Spiroschau- 

 dinnia icterohcBmorrhagicB, which may have its reservoir in rats, 

 from which it probably escapes in the urine, and after living in 

 water enters via the alimentary canal or the skin. It is believed to 

 have been caused, but very rarely, as the result of a rat -bite. It is 

 introduced here as a convenient place, though not known to be due 

 to lice. 



Parasite. 



Host. 



Reservoir. 



Method of Infection. 



Spiroschaudinnia 

 icterohismorrhagice. 



Man. 



Rats (?). 



Contaminated water (?). 



