254 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 Peru would impress one 

 with the similarity to the distribution of the Rocky Mountain fever 

 and would lead to the conclusion that the aetiological 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. 



