846 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



In Central America a spirochaete, which causes a disease almost identical 

 with tick fever, is carried by Ornithodoros chinche. 



Spirochceta duttoni is a slender organism measuring from 14/i to i6jii in length; its 

 thread-like body lies in a number of waves, which vary greatly in number, according 

 to the way in which the preparation is made; consequently, the number of waves is 

 , not a constant character which can be relied upon for the identification of this species 

 of spirochaete. This spirochaete is composed of an outer ectoplasmic sheath, and of 

 an interior composed largely of chromatin; the sheath extends at either end into 

 flagellum-like prolongations. Multiplication is accomplished 

 by transverse binary division. Sometimes, perhaps most 

 often toward the end of an attack of fever the spirochaetes 

 coil up tightly, within a cyst-like matrix. Such encysted 

 forms may lie within cells, i.e., liver cells, and spleen cells; 

 they are seen most frequently in the liver and spleen, and 

 they are always present in the alimentary canal of ticks 

 which have ingested spirochaete-infected blood. The chro- 

 matin of both free and encysted spirochaetes may be frag- 

 ' mented, more or less regularly. In the tick, cysts, containing 



, ,j \,'~t'J'?.'^ a spirochaete with fragmented chromatin, burst and set free 

 hata duttom. (After ^, '^ , j- . .• c ■ j.- ^ u v 



Doflein.) '■"^ granules of chromatm. Some mvestigators believe 



that each granule develops into a spirochaete, others that 

 this represents a degeneration and destruction of the parasite. It is not impossi- 

 ble that some such method of multiplication occurs in man. 



The form and the exact way in which the spirochaete is transmitted by the tick is 

 not known. It is probable that a tick, once infected, never loses its power to trans- 

 mit the disease; the infection may be transmitted^from mother to daughter, through 

 at least three generations of ticks. 



The ticks hide during the day and feed at night. The wound produced by theil 

 bite is insignificant. 



An incubation period of about five days intervenes between the tick 

 bite and the appearance of symptoms. The fever is characteristic; it 

 rises rapidly to, perhaps, 105° and it remains high for from three to five 

 days. It then falls suddenly and there is no fever for from five days 

 to two weeks. Then the temperature rises again and there may be from 

 three to six such recurrences of fever before the illness ends. The 

 definite periodicity of the relapses probably depends upon some more 

 or less regular developmental change in the spirochaetes since the latter 

 are always most numerous in the blood during the height of the fever. 

 The disease is not often fatal and "606" is a specific treatment for it. 

 It can be easily prevented by avoiding tick bites. 



