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Arthropod Transmission of Disease 
The disease is confined to South America and to definitely limited 
areas of those countries in which it does occur. It is especially 
prevalent in some parts of Peru. 
The causative organism and the method of transfer of verruga 
are unknown. Castellani and Chalmers pointed out in 1910 that the 
study of the distribution of the disease in Pem would impress one 
with the similarity to the distribution of the Rocky Mountain fever 
and would lead to the conclusion that the astiological cause must in 
some way be associated with some blood-sucking animal, perhaps an 
arachnid, and that this is supported by the fact that the persons 
most prone to the infection are those who work in the fields. 
More recently, Townsend (1913), in a series of papers, has main¬ 
tained that verruga and Carrion’s disease are identical, and that they 
are transmitted to man by the bites of the Psychodid fly, Phlebotomus 
verrucarum. He succeeded in producing the eruptive type of the 
disease in experimental animals by injecting a physiological salt 
trituration of wild Phlebotomus flies. A cebus monkey was exposed 
from October 10 to November 6, by chaining him to a tree in the 
verruga zone, next to a stone wall from which the flies emerged in 
large numbers every night. Miliar eruption began to appear on the 
orbits November 13 and by November 21, there were a number of 
typical eruptions, with exudation on various parts of the body 
exactly like miliar eruptive sores commonly seen on legs of human 
cases. 
An assistant in the verruga work, George E. Nicholson, contracted 
the eruptive type of the disease, apparently as a result of being bitten 
by the Phlebotomus flies. He had slept in a verruga zone, under a 
tight net. During the night he evidently put his hands in contact 
with the net, for in the morning there were fifty-five unmistakable 
Phlebotomus bites on the backs of his hands and wrists. 
Townsend believes that in nature, lizards constitute the reservoir 
of the disease and that it is from them that the Phlebotomus flies 
receive the infection. 
Cancer 
There are not wanting suggestions that this dread disease is 
carried, or even caused, by arthropods. Borrel (1909) stated that 
he had found mites of the genus Demodex in carcinoma of the face 
and of the mammas. He believed that they acted as carriers of the 
virus. 
