TRANSMISSION OF RELAPSING FEVER 399 



tensive fight against lice. It is practically certain that no nation 

 which profits by the discoveries of science will ever again be 

 cursed by a great typhus epidemic. 



The r61e of lice in the transmission of the European and North 

 African form of relapsing fever has long been suspected but was 

 not proved until 1913, when Nicolle and his fellow-workers 

 scientifically demonstrated it in Tunis and Algeria. Noting 

 that the louse was the only constant factor affecting the occur- 

 rence of the disease, these French workers undertook extensive 

 experiments which resulted in proving that the body louse, and 

 probably also the head louse, serves as a medium for the develop- 

 ment of the spirochsetes of relapsing fever, and that these insects 

 transmit the disease not by biting but by inoculation of the 

 wounds which they make with the infected contents of their 

 bodies when crushed. 



Nicolle and his associates also showed that sometimes, at least, 

 the spirochaetes, probably in the granule stage, are hereditarily 

 transmitted through the eggs to the young of the next generation, 

 as is the case with the African relapsing fever parasites in the 

 tick. Experiments on the transmission of the relapsing fever of 

 Algeria with other parasites such as bedbugs, fleas, biting flies 

 and ticks were negative. Some observers, however, believe that 

 in Europe other insects also, notably bedbugs, may be instru- 

 mental in transmitting relapsing fever. The evidence furnished 

 by the epidemiology of the disease is, however, very strongly in 

 favor of lice as the normal transmitters. The Indian form of 

 relapsing fever is also probably transmitted by lice. Further 

 details of the development of the spirochsetes in the lice are 

 given in Chapter IV, p. 44. 



Being transmitted by lice, relapsing fever shows the same pe- 

 culiarities of occurrence as does typhus; epidemics always rage 

 fiercest in winter, and usually break out during war times. 

 Serbia, which was so stricken by typhus, was held in the grip 

 of an epidemic of relapsing fever earlier in the war. 



Lice may also serve as mechanical transmitters of still other 

 diseases. The bacilli of bubonic plague have been found alive 

 in both body lice and head lice taken from victims of the disease, 

 and both this species and the body louse have been experimen- 

 tally proved to be able to transmit plague from rodent to rodent 

 in Java. De Raadt in Java infected rodents with plague by in- 



