MEDICAL ENTOMOLOGY — HOWARD. 575 



the Australasian life zone. In Formosa, Koizumi has inculpated 

 Desvoidea obturbans in the same relation. 



The spirochaetes, protozoal organisms of wide distribution, have, 

 however, been shown to be the cause of other diseases of man and 

 animals and to be insect-borne, but in nearly all of these the arthro- 

 pod carrier is a tick rather than a true insect, and it is interesting to 

 note that with at least one of these the infected tick transmits the 

 disease to its offspring just as Theobald Smith found to be the case 

 many years earlier with the Texas fever of cattle. 



The series of discoveries of spirochaete-tick diseases began shortly 

 after the establishment of yellow fever mosquito relation, by the 

 findings of Ross and Milne in Uganda, and Dutton and Todd in the 

 Congo, in 1904, of the spirochaete cause of the so-called "African 

 relapsing fever " and its tick vector— Ornithodoros moubata. That 

 this fever resulted from the bite of a special tick was long known 

 to the natives of Africa, but just as in the case of the Nagano, disease 

 of cattle, which will be referred to shortly, the fever was supposed 

 to be due to some special virulence of the tick. In this case the 

 carrier occurs abundantly in native huts and feeds upon birds and 

 mammals as well as upon man, resembling the bedbug in that it 

 works by night. 



Another spirochaete disease is the "European relapsing fever," 

 and as early as 1897 Tictin infected monkeys with this disease by 

 inoculating them with bedbugs which had fed upon a patient 48 

 hours earlier. Therefore bedbugs are supposed to be the carriers 

 of this disease, although the evidence is not complete. 



In 1903, however, Marchoux and Salimbeni, working in Brazil 

 under the auspices of the Pasteur Institute of France, secured con- 

 clusive evidence of the transference of another spirochaete disease, 

 known as the spirochaetosis of domestic fowls, by a tick known as 

 Argas persicus. Still another proved relation of the kind is that of 

 the spirochaetosis of cattle in the Transvaal, where the disease is 

 carried by a tick known as Margarofus decoloratus. 



Even antedating the work of the yellow fever commission was the 

 extremely important work of Col. David Bruce, of the British Army, 

 with the so-called Nagana or tse-tse fly disease of cattle in Africa. 

 In this case the causative organism was found to be another type of 

 protozoan of the genus Trypanosoma, and it was this organism, 

 transmitted by the bite of a tse-tse fly from sick cattle to healthy 

 cattle which caused the disease which had previously, just as in the 

 case of the "African relapsing fever," been attributed solely to the 

 virulence of the bite, " fly sickness of cattle " having been known to 

 all African explorers. Here, then, is another group of microorgan- 

 isms which cause disease in warm blooded animals and are trans- 

 mitted by insect bites. In this case it was long a matter of doubt 



