April, '13] TOWNSEND: VERRUGA AND TICKS 223 



and valleys. This may be done more or less by man and animals 

 on the trails passing the embouchures of these tributary quebradas 

 and canj'ons, the ticks becoming attached to their bodies or clothing. 

 Almost certainly great numbers of the infective adult ticks are washed 

 down the very steep inclines of these tributary quebradas during the 

 rainy season, and spread themselves over the surrounding areas in 

 their search for large animals on which to engorge. It is well known 

 that the newly transformed adult ticks will live for as long as a year 

 without food if the\^ do not find a host in the meantime. Thus man 

 and animals passing the mouths of these tributary canyons are apt 

 to gather these ticks unawares, and man is especially apt to be bitten 

 by them for hours at a time if he sleeps many consecutive nights in 

 such localities. The long life of the infective adult ticks, provided 

 they do not find a host, explains why verruga may be contracted at 

 various times of the year quite irrespective of seasons but in more or 

 less isolated cases. The March and April season of high prevalence 

 of verruga is probably due to the large numbers of ticks washed down 

 during the rainy season in the hills. An unusually rainy season, or a 

 season in which there is greater precipitation during a given time, caus- 

 ing swifter freshets which reach farther than usual, may be responsible 

 for the occasional extensions of the disease which have been noted, as 

 for instance, the Matucana occurrence of 1912. There are doubtless 

 many areas still unknown where the reservoir fauna breeds and the 

 tick transmitters are to be found on the ground in large numbers. 



Judging from the probabilities, it is therefore advisable to use much 

 caution in order to avoid the attachment to the person of ticks of 

 whatever kind throughout the western face of the central Andean 

 region below 11,000 feet. Any ticks of the genus Dermacentor to be 

 found on the ground or on large animals in this region may be infected 

 with verruga. Those already attached to large animals will hardly 

 leave them of their o^Yn. accord for man, but those on the ground that 

 are still searching for hosts are particularly to be feared. The danger is 

 always greatest at night, while man is asleep, for their attachment does 

 not wake him and is therefore not felt. Two species of ticks, Mar- 

 garopus australis from the bodies of cattle, and Ornithodoros megnini 

 from the ears of horses, cattle and sheep, have been taken by me in 

 the Chosica region, but neither one has any relation to verruga. Both 

 pass all stages including engorgement on the same host. It is the 

 ticks which drop from the small hosts in the nymph stage and seek 

 new hosts in the adult stage that are to be guarded against as possi- 

 ble verruga carriers. These may belong to any one of the genera Der- 

 macentor, Rhijncephalus , Hoemaphysalis, and Amblyomma, one or more 

 species of all of which are known to drop to the ground for both moults. 



As to the possible identity of the native fauna which constitutes 



