12 BULLETIN 986, U. S. DEPARTMENT OF AGRICULTURE. 
In this country Prof. Herrick (4, p. 317-325) has made observa- 
tions on chiggers in various parts of the United States. He says: 
Very often a slight fever accompanies the eruptions and the patient is liabie 
to lose sleep and suffer almost unbearable torture. 
In regard to the general disturbances caused chickens the same 
authority states (5, p. 258-260) : 
The chicks seem to contract a diarrhea, grow weaker and weaker, and 
finally die. 
Where the attacks from chiggers are slight, as a rule, no general 
symptoms are produced. When there is a sudden attachment of 
several hundred larve general symptoms may result. The irritation 
produced by such a large number may prevent sleep for several nights 
in succession and thereby upset or disturb digestion. Also, a peculiar 
nervous disturbance may be caused. This may be brought about by 
toxins injected by the larvee or by some other cause. 
During the months of July, August, and September, 1919, the 
writer on many occasions was attacked by chiggers. Some of these 
attacks were severe and on more than one occasion blood-red spots | 
larger than a half dollar were left. Asa result of these repeated at- 
tacks a peculiar nervous effect was produced. During parts of the 
day a feeling of lethargy was noticed, yet to many things a hyper- 
sensitiveness was produced. This irritable state became sd pro- 
nounced at times as to make productive work all but impossible. 
With this upsetting of the nerves, interference of bodily processes 
was observed to a considerable extent. It was only after the cool 
days of November that a normal condition was restored. 
RELATION TO DISEASE. 
Until the work was begun in Japan on the cause of flood or river 
fever (“ tsutsugamushi-krankheit ”) some 15 years ago, chiggers had 
enjoyed an almost complete freedom from suspicion as actual disease 
carriers. As the work on this deadly disease progressed, however, 
they were soon held to be implicated in some way and finally shown 
to be the active carriers of the virus of this disease. 
The results of various Japanese workers shew that this disease is 
caused by a nonfilterable virus which is transmitted by means of the 
chigger bites to man. The natural reservoir is apparently the normal 
hosts of the chiggers, chiefiy field mice, as only a small percentage 
of the larvee are infected. Kitashima and Miyajima (7, p. 232) state 
that while “ tsutsugamushi-krankheit ” is similar to typhus fever and 
Rocky Mountain spotted fever in that the virus is nonfilterable and 
arthropod-borne, yet the disease itself is quite different from either. 
River fever is a very deadly disease, as about one-third of all the 
cases are fatal. The only regions of the country affected are those: 
along the water courses or in lowlands. Various attempts have been 
