488 OTHER BLOOD-SUCKING FLIES 



but only immediately after the infective feed. Human trypano- 

 some diseases have been suspected of being transmitted likewise, 

 but there is yet no proof that this takes place. 



The most important disease disseminated by tabanids is an- 

 thrax. This is a bacterial disease to which nearly all herbivorous 

 animals and man are susceptible, and which is very destructive, 

 sometimes killing over 75 per cent of its victims. The bacilli 

 which cause the disease gain entrance to the body either through 

 abrasions of the skin to the blood, through spores in the air to 

 the lungs, or through contaminated food to the intestine. The 

 bacilli have been found in the alimentary canal of tabanids 

 which have fed on dying or dead victims, and animals inoculated 

 with these bacilli died of anthrax. That these flies could trans- 

 mit the disease not only when crushed so that the contents of the 

 digestive tract could contaminate the wound, but also by their 

 bites, has been stated many times, and has recently been observed 

 in China under conditions which placed it beyond doubt. The 

 method of transmission is purely mechanical and probably oc- 

 curs only when a fly which has been feeding on a diseased animal 

 finishes its meal on a healthy animal or on a human being, the 

 disease germs adhering to the mouthparts long enough to be 

 transferred to the new animal. The stable-flies, Stomoxys, and 

 other biting flies which will attack two or more animals in quick 

 succession are equally as dangerous as anthrax carriers. 



Tabanids have often been accused of causing diseases similar 

 to, if not identical with, oriental sore. In the intestines of vari- 

 ous tabanids there exist flagellate parasites belonging to the 

 genus Herpetomonas, and it is believed that if these should ac- 

 cidentally gain entrance to the flesh of a human being by contami- 

 nation of the puncture made by the host fly, they might assume 

 the form of Leishman bodies and multiply to a sufficient extent to 

 cause a local sore. Obviously such implanted parasites would 

 be permanently side-tracked, and would stand little chance of 

 ever being released by a fly of the species in which they nor- 

 mally live. Such a theory is proposed to explain the sporadic 

 cases of leishmaniasis of the skin which occur in Panama and 

 other places, and which are usually reported to develop at the 

 site of a horsefly bite. In Sao Paulo, Brazil, a form of leish- 

 maniasis is very common among forest workers, even in wild 

 uninhabited regions. The fact that the disease is contracted 



