Arthropods and Disease Transmission 349 



insects and insect-transmitted diseases. Interested students are 

 referred to this work for additional background material, but a few 

 historical highlights will be presented here. 



One of the earliest proposals that insects might be instrumental 

 in the dissemination of disease was made in 1577 when Mercurialis 

 expressed the idea that bubonic plague could be transmitted by 

 flies which had been in contact with the corpses of persons who 

 had succumbed from this disease. Relatively few significant con- 

 firmatory studies were conducted for about three centuries, but a 

 sudden impetus was provided to this field of science by a series 

 of fundamental discoveries near the close of the nineteenth century. 

 The finding in 1893 by Smith and Kilbourne that the cattle tick 

 Boophilus annulatus transmits Babesia bigemina, the etiological 

 protozoan in Texas cattle fever, is a milestone in insect micro- 

 biology. These workers also discovered that the protozoan is 

 transmissible through the egg of the tick to succeeding generations. 



Other significant discoveries during this same period included 

 the finding by David Bruce ( 1895 ) that the tsetse fly transmits the 

 trypanosome of sleeping sickness; the discovery by Ronald Ross 

 in 1897 that malaria is carried by the Anopheles mosquito; 

 Simond's report in 1898 that plague organisms are transmitted to 

 rats by infected fleas; and that yellow fever virus is spread by 

 the mosquito Aedes aegypti (Finlay 1881; Reed 1900). 



Each of these discoveries opened up new fields of attack for 

 man in his fight to control debilitating and killing diseases. Re- 

 search aimed at the destruction of the vectors and the development 

 of therapeutic measures once a patient has contracted the disease 

 has paid rich dividends during the last fifty years. These diseases 

 have not been eradicated, but their control is better today than 

 ever before in man's history. 



IMPORTANT INSECT VECTORS 



FLIES 

 Insects have long been considered to be undesirable as far as 

 human habitation is concerned. In addition to their being a 

 nuisance, these arthropods may also serve as passive or as active 



