512 RELAPSING FEVER 



Varieties. As already stated, relapsing fever has been studied 

 in different parts of the world, and, apart from the African tick 

 fever, European, Asiatic, and American types have been dis- 

 tinguished. Differences have been made out with regard to 

 clinical features, pathogenic effects, and immunity reactions. 

 It has been shown, for example, by the work of Novy, Strong, 

 and Mackie, that the American spirochsete is probably a distinct 

 species, as animals immunised against it are still susceptible to 

 infection by the European and Asiatic organisms, and vice versa. 

 The relationship between the two latter is certainly closer, and 

 no distinct immunity differences have been established. Re- 

 lapsing fever in Asia is evidently a much more severe disease 

 than in Europe ; Mackie gives the mortality in Bombay at the 

 comparatively high figure of 38 per cent. But differences in this 

 respect, as well as in pathogenic effects, may simply depend on 

 variations in virulence. At present no definite statement can be 

 made on this point. Sergeant and Foley have recently described 

 a type of relapsing fever occurring in Algiers, which they consider 

 to be different from the recognised forms, and have given the 

 name sp. berbera to the organism concerned; and Balfour has 

 observed cases in Khartoum which he thinks are probably of the 

 same nature. 



The fact that tick fever) and other spirilloses are con- 

 veyed by the bites of insects makes it extremely probable that 

 relapsing fever is transmittedjin this way. At first the bed-bug 

 was believed to be the vehicle of transmission, and the experi- 

 ments of Karlinski and of Tictin, which showed that the spiro- 

 chsetes might remain alive and virulent in the body of this 

 insect for some time after it had sucked the blood of a patient, 

 lent some support to this view. ; Attempts to transmit the 

 disease by means of the bites of bugs were, however, generally 

 unsuccessful ; Mackie produced the disease in only one out of 

 six monkeys used for this purpose, though large numbers of bugs, 

 which had bitten relapsing fever patients, were used. On in- 

 vestigating an epidemic of the disease, however, he obtained 

 a considerable amount of evidence on epidemiological grounds 

 that the disease was carried by the body louse. He also found 

 that the spirochsetes in the blood which had been ingested under- 

 went great multiplication about three days afterwards, and 

 formed large tangled masses in the stomach contents. The 

 view that the louse is the agent of transmission of the human 

 disease is strongly supported by the experiments of Manteufel, 

 who was able to transmit infection from rat to rat in nearly 

 60 per cent, of the experiments made, whereas he obtained 



