12 BULLETIN 986, U. S. DEPARTMENT OF AGBICTJLTTJRE. 



In this country Prof. Herrick (.£, 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 liable 

 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 larvae 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 larvae 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. As a 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 so 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 show 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, chiefly field mice, as only a small percentage 

 of the larvae 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 



