488 THE SPIROCHETES 



fever. The majority of cases seen in Europe are mild,' the mortality being only 2-4 

 per cent, but during the World War severe cases resembling yellow fever were oc- 

 casionally reported.^ In Scotland, among miners, Buchanan found the mortality to 

 be as high as 30 per cent. 



The incubation period is six to twelve days; the initial fever is high and is fol- 

 lowed by nausea and vomiting, headache, epistaxis, and muscular pains in the limbs. 

 Bronchitis of moderate severity, jaundice, and mild or severe parenchymatous ne- 

 phritis develop, and spots of hemorrhage appear on the skin. In most cases there 

 is a second rise of temperature late in the second week of illness. In severe cases the 

 vomitus or stools may contain fresh or altered blood, and hematuria is not uncom- 

 mon; a moderate degree of anemia is usual. Convalescence is slow, and the patients 

 suffer weakness for months. After several days of illness the spirochetes appear in 

 the urine, being most numerous about the fifteenth day. They have usually disap- 

 peared by the fortieth day, though in one case they were excreted as late as the sixty- 

 fifth day. In fatal cases death occurs during the second or third week, occasionally 

 as early as the eighth or ninth day. 



One attack prevents reinfection for a long time, immunity being as durable as 

 that from yellow fever. A specific lysin for L. icterohaemorrhagiae appears in the 

 blood and may be detected several years after recovery.^ 



The natural reservoir of infection in the case of L. icterohaemorrhagiae is the wild 

 rat, as first pointed out by Inada and Ido and their collaborators,^ and substantiated 

 by numerous observers in various parts of the world. s The organism may be directly 

 demonstrated in the kidneys of apparently healthy wild rats, or transmitted to guinea 

 pigs by inoculation of suspension of the kidney tissue, and the strains from rats have 

 the same morphological, pathogenic, and immunological properties as those isolated 

 from human cases. The proportion of rats infected varies in different places. In 

 New York'' it was only 4 per cent, in Guayaquil'' it was 60 per cent, in England and 

 Scotland it was about 30 per cent. The Japanese workers believed that the occurrence 

 of infectious jaundice among miners was due to contamination of the stagnant water 

 and soil of the mines with rat urine, and their theory was substantiated by the rapid 

 decline in the incidence of the disease after drainage of the mines and disinfection of 

 the soil. The actual presence of L. icterohaetnorrhagiae in the water of mines was 

 proved only recently by Buchanan. 



There is, however, another theory regarding the source of infection with L. ic- 



' Ryle, J. A.: Quart. J . Med., 14, 139. 1921. 



^Dawson, B., and Hume, W. E.: ibid., 10, 90. 1916-17. 



3 Inada, R., Ido, Y., Hoki, R., Ito, H., and Wani, H.: loc. cit. 



t Ido, Y., Hoki, R., Ito, H., and Wani, H.: J. Exper. Med., 26, 341. 1917. 



s Courmont, J., and Durant, P.: Bidl. el mem. Soc. med. d. hop. de Paris, 41, 115. 1917; Jobling, 

 J. W., and Eggstein, A. A.: J.A.M.A., 69, 1787. 1917; Coles, A. C: J. Parasitol., 11, i. 1918; 

 Ribeyro, R. E.: Cron. med., Lima, 35, 157. 1918; Smillie, W. G.: Bull. Soc. path, c.vo!., 13, 56. 1920; 

 Pereiro da Silva, E.: Ccmpt. rend. Soc. de biol., 86, 1043. 1Q22; Carrieu, IM. F., and Sollier, N.: 

 ibid., p. 99. 1922; Anigstein, L.: 7. Trop. Med., 26, 81. 1923; Bonne, C: Compt. rend. Soc. de biol., 

 go, 668. 1924. 



^Noguchi, H.: J. Exper. Med., 25, 755. 1917. ' Noguchi, H.: ibid., 30, 95. 1919. 



