The Transmission of Leprosy by Mosquitoes and its Prophylaxis*

This paper was presented to the Section of Tropical Medicine, of the 7 CruiseCongress of Pan American Medical Association, whose invitation to be present at the meeting held at Havana, in January 1938, I was unable to accept. The subject was chosen as leprosy is one of the most important medical problems as yet unsolved and I do not believe its eradication to be possible until methods of prophylaxis are subjected to an entirely different approach. Following the paper a series of experiments are suggested for the demonstration of the possibility of the transmission of pathogenous germs belonging to the same group as that of leprosy by mosquitoes. They and the methods to be used were first suggested by me at a meeting of the Brazilian Academy of Science, when I received its Einstein Prize (1935). The idea of the transmission of leprosy by blood-sucking insects is not new. It was stated by various observers already at a time when our knowledge of their importance was still quite rudimentary. The supposition then prevalent was that the insects functioned somewhat like vaccine-lancets, first inserting their mouth-parts in the diseased tissue of a leper, then in the healthy skin of another person, thus infecting him or her. This simple point of view did not, however, agree sufficiently with the mechanism of propagation observed in other important mosquito-transmitted diseases, to make it generally acceptable. Let us recall some of these, for instance the first observations on human blood-parasites developing in mosquitoes. These were made as early as 1877 on Filaria bancrofti by Manson. The process of transmission however, was only explained in 1900 by Bancroft and Low. Before this (1888-1889), Smith and Kilbourne had already demonstrated the transmission of Texas fever by ticks, and Ross and Grassi that of malaria by mosquitoes (1898). Finally the transmission of yellow-fever by a house-mosquito was experimentally established in Cuba by Reed and Caroll and confirmed in the same year in São Paulo (Brazil), by some volunteers, among whom Dr. E. Ribas and the author of this paper. It was only after these investigations had taken place and were confirmed by the results of anti-mosquito prophylaxis that the importance of blood-sucking animals in the spreading of infectious diseases was understood. It also became evident that this is no simple process of puncture and inoculation but that the change of hosts is essential to the development of the blood-parasite, and also that a lapse of time is necessary before the intermediate blood-sucking host becomes The Transmission of Leprosy by Mosquitoes and its Prophylaxis*