252 Arthropod Transmission of Disease 



Service summarize their conclusions in the statement, (i) that it is 

 dependent on some yet undetermined fault in a diet in which the 

 animal or leguminous protein component is disproportionately large 

 and (2) that no pellagra develops in those who consume a mixed, 

 well-balanced, and varied diet, such, for example, as that furnished 

 by the Government to the enlisted men of the Army, Navy, and 

 Marine Corps. 



Leprosy 



Leprosy is a specific, infectious disease due to Bacillus lepra, and 

 characterized by the formation of tubercular nodules, ulcerations, 

 and disturbances of sensation. In spite of the long time that the 

 disease has been known and the dread with which it is regarded, 

 little is known concerning the method of transfer of the causative 

 organism or the means by which it gains access to the human body. 



It is known that the bacilli are to be found in the tubercles, the 

 scurf of the skin, nasal secretions, the sputum and, in fact in prac- 

 tically all the discharges of the leper. Under such conditions it is 

 quite conceivable that they may be transferred in some instances 

 from diseased to healthy individuals through the agency of insects 

 and other arthropods. Many attempts have been made to demon- 

 strate this method of spread of the disease, but with little success. 



Of the suggested insect carriers none seem to meet the conditions 

 better than mosquitoes, and there are many suggestions in literature 

 that these insects play an important rdle in the transmission of 

 leprosy. The literature has been reviewed and important experi- 

 mental evidence presented by Currie (1910). He found that mosqui- 

 toes feeding, under natural conditions, upon cases of nodular leprosy 

 so rarely, if ever, imbibe the lepra bacillus that they cannot be 

 regarded as one of the ordinary means of transference of this bacillus 

 from lepers to the skin of healthy persons. He believes that the 

 reason that mosquitoes that have fed on lepers do not contain the 

 lepra bacillus is that when these insects feed they insert their probos- 

 cis directly into a blood vessel and thus obtain bacilli-free blood, 

 unmixed with lymph. 



The same worker undertook to determine whether flies are able 

 to transmit leprosy. He experimented with five species found in 

 Honolulu, Musca domestica, Sarcophaga pallinervis, Sarcopkaga 

 barbata, Volucella obesa and an undetermined species of Lucilia. 

 The experiments with Musca domestica were the most detailed. 



