April, '13] TOWNSEND: VERRUGA AND TICKS 215 



Central railway, 2,000 men were employed in tunnel work during the 

 year. Among these there occurred 200 known deaths from verruga, 

 and it is practically certain that still further deaths occurred among the 

 many laborers who left the works and whose history was not followed 

 up. The general experience with laborers on the Central railway has 

 been that five or six nights passed successively within the verruga 

 district causes the fever to appear in 75 per cent to 80 per cent of the 

 workmen in a camp. In a week or so nearly all are certain to contract 

 the disease. No animals of any kind were employed by the laborers 

 in any of this work. Mosquitoes and buffalo gnats in abundance, as 

 well as bedbugs and fleas, occur at Chosica and throughout the greater 

 part of the verruga districts. 



During the early stages of the work in the building of the Central 

 or Oroya railway up to 1876, when the road was completed into Chicla, 

 thousands and tens of thousands of laborers Avere emploj^ed, largely 

 strong healthy Chileans, as many as 8,000 being carried on the pay- 

 rolls at one time. During this period the recorded mortality from 

 all causes — disease and accident — was some 7,000. A large majority 

 of these deaths was doubtless due to verruga, the result of carrying 

 the road through the verruga district of the Rimac which has given its 

 name to Verrugas Bridge. 



After this hurried historical survey of verruga we may proceed to 

 make certain deductions from the data at hand, which may throw some 

 light on the etiology and transmission of the disease. It seems prac- 

 tically proved that Oroya or quel^rada fever and verruga eruption are 

 the same disease. The history of the case of the American engineer 

 Wilson who contracted the fever in the seventies of the past century 

 and developed the eruption after returning to North Am.erica, indi- 

 cated the identit}^ of the two, and this was verified by Carrion's ex- 

 periment upon himself in the eighties. Carrion produced the fever 

 in himself by inoculation, after the manner of a vaccination, with 

 blood from a verruga tumor. This experiment, which unfortunately 

 terminated fatall}', not only clinched the etiological identity of the 

 fever and eruption phases, but also demonstrated that the disease is 

 transmissable by inoculation. 



The apparently established inoculability of the disease is the basis 

 on which rests the arthropod- transmission theory. Dr. Julian Arce, 

 of the National Academy of Medicine at Lima, was the first to suggest 

 that verruga may be contracted through the agency of some animal 

 bloodsucker. Later Dr. Darling, in the paper above mentioned, sug- 

 gested "a tick or mosquito, or other suctorial invertebrate having a 

 peculiar altitudinal distribution" as the carrier of verruga. It is well 

 known that the disease can not be transmitted by mere contact as long 



