396 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 3 



distribution does not appear to tally exactly with that of any one 

 species of possible vector, but experimental work indicates that the 

 disease is carried by several species of ticks and probably by other 

 arthropods, notably flies. The investigations of Dr. Gerald Dikmans 

 of the Bureau of Animal Industry showed that anaplasmosis can be 

 carried by the cattle tick. In the case of this tick the malady is trans- 

 mitted through the egg to the next generation. Dr. C. W. Rees, also 

 of the Bureau of Animal Industry, has demonstrated the transmis- 

 sibility of the disease by the brown dog tick, Rhipicephalus sanguin- 

 eus Lat. While this is interesting scientifically, apparently it has 

 little practical bearing, as this tick, especially in thisi country, is re- 

 stricted very closely to the dog as a host, although it can be forced to 

 attach to cattle. It is markedly domestic, being closely associated 

 with the habitat of dogs. Rees' subsequent demonstration that ana- 

 plasmosis can be conveyed by the American dog tick is more signifi- 

 cant, as that tick freely attacks cattle and has a rather wide distribu- 

 tion in nature. Rees has also shown that the disease may be con- 

 veyed by B. annulatus cmstralis Fuller and by Ixodes recinus 

 scapularis Say. 



The results thus far obtained in transmission experiments strongly 

 suggest that many species of ticks may be concerned in the trans- 

 mission of this disease and that any of those commonly attacking 

 cattle should be regarded with suspicion. 



TICKS IN RELATION TO TULAREMIA 



Tularemia or rabbit fever is widespread in this country, and it is 

 regarded as a serious malady. While it is most commonly contracted 

 by handling diseased rabbits, ticks are clearly of importance as car- 

 riers of it. Parker and Spencer, of the United States Public Health 

 Service, have established the fact that the Rocky Mountain spotted 

 fever tick and the common rabbit tick can transmit the disease, and 

 that these ticks are the chief carriers of it among rodents in the 

 Northwest. Parker and Green and Wade have also shown that 

 the disease occurs in quail and other game birds, and it may well be 

 the cause of the epizootics which devastate the wild bird and animal 

 life from time to time. Since these ticks are biological hosts for the 

 disease organism, Pasteurella tularense^ that is, the infection acquired 

 in one tick stage is passed on to the next, they constitute a sure means 

 of perpetuating and spreading the disease among lower animals, 

 thus increasing the danger to man. A number of instances where 

 human cases have been contracted from the bite of the American dog 

 tick and the Pacific Coast tick {Berniacentor occidentalis Neum.) 

 have been found. Probably a number of other species of ticks play 

 a part. 



