468 THE SPIROCHETES 



MODES OF TRANSMISSION 



The transmission of the blood-inhabiting spirochetes to man is effected through 

 the bite of an infected blood-sucking insect or arthropod. The transmitting agent in 

 each instance is under natural conditions specific. Other blood-suckers may be in- 

 fected, but the artificially infected insects are not good transmitting agents. Both 

 body lice and bedbugs, for example, can be infected by sucking the blood of a patient 

 with European relapsing fever, but only the lice are able to transmit the disease. The 

 survival of the infecting organism in the bedbug can be demonstrated by inoculation 

 of the crushed body of the insect into a susceptible animal. It is possible, therefore, 

 that bedbugs may bring about infection if crushed on an injured skin surface. 



Treponema recurrentis, of European relapsing fever, is transmitted by the body louse, 

 Pediculus vestimenti.^ Infection can be transmitted in experimental animals per os as well 

 as subcutaneously. T. duttoui, of African tick fever, is normally carried by Ornithodoros 

 moubala,' and hereditary transmission occurs in the tick. T. anserinum, of fowl relapsing 

 fever, is transmitted by the tick Argas persicus (miniatiis).^ L. iderohaemorrhagiae (Weil's 

 disease, or hemorrhagic jaundice) is carried by rats^ and thought to be disseminated through 

 the urine; L. hebdomadis (seven-day fever of Japan) is carried by the field mouse.s L. ic- 

 terohaemorrhagiae has, however, been artificially transmitted by insects.* L. interrogans, of 

 yellow fever, is conveyed by the mosquito, Aedcs aegyptiJ T. pallidum is usually transmitted 

 directly through contact. It was once thought that excoriation of the mucous membrane 

 was necessary for invasion, but the investigations of Brown and Pearce^ show that the or- 

 ganism can penetrate the unbroken skin. Extragenital infections are not uncommon among 

 physicians and nurses, for direct contact with Hving T. pallidum in any way may lead to in- 

 fection. Hereditary transmission occurs to the second and even to the third generation. In- 

 fection with 2\ pcrtciiuc probably occurs through direct contact with the secretion of the 

 yaws lesion. T. cuniculi, of spontaneous rabbit venereal disease, is apparently transmitted 

 as a rule by coitus.' 



IMMUNITY 



The phenomena of immunity in spirochetal diseases vary with the type of or- 

 ganism. In general, it appears that the spirochetes which produce an acute febrile 

 disease, ending in crisis, or of short duration, leave in the convalescent man or animal 

 a state of more or less complete immunity of variable duration. The organisms of 

 the relapsing fever group confer upon man active immunity lasting about one and a 

 half years, while the leptospiras give an immunity enduring for many years. The tis- 



' NicoUe, C, Blaizot, L., and Conseil, E.: Compt. rend. Acad, dc sc, 155, 481. 191 2. 



^Button, J. E., and Todd, J. L.: Bril. M. J., 2, 1259. 1905. 



3 Marchoux, E., and Salembeni, A.: Ann. dc I'lnsl. Paslcur, 17, 569. 1903. 



4ldo, Y., Hoki, R., Ito, H., and Wani, H.: /. Expcr. Med., 26, 341. 1917. 



sido, Y., Ito, IL, and Wani, 11.: ibid., 28, 435. 1918. 



'' Uhlenhuth, P., and Kuhn, 1'.: Zlschr. Ily!^. 11. Infcklionsknnikli., 84, 517. 1917; Blanc, G.: 

 Compt. rend. Soc. dc bioL, 83, 263. 1920; Bonne, C: ibid., 91, 242. 11)24. 



' Noguchi, H.: J. E.xpcr. Med., 30, 401. 1919; Koshina, M., Shiozawa, S., and Kitajama, K.: 

 ibid., 42, 873. 1925. 



^ Brown, W. H., and Pcarcc, L.: Proc. Soc. E.xper. Biol, c^ Med., 18, 200. 1921. 



' Kolle, W., and Ritz, II.: Dermal. Zlschr., 27, 319. 1919. 



