THE RELATION OF MOSQUITOES TO MAN. 

 THE CARRIAGE OF DISEASE BY MOSQUITOES. 



That certain mosquitoes are an essential factor in the propagation of certain 

 diseases is now well demonstrated and generally accepted. In every case where 

 such relation of the mosquito has been proved the role of the insect is not that of 

 a purely mechanical carrier or transmitter, as is, for example, the conveyance of 

 typhoid fever by the house fly. The diseases in question are caused by organisms 

 which have a complex life-cycle, part of which is passed in man and part in the 

 mosquito, and in the absence of one or the other of the hosts their existence or 

 continuance is impossible. In other words, the causative organisms of these 

 diseases, as far as we know them, are animal parasites. These parasites can 

 exist only in definite hosts. This restriction goes so far that a given parasite is 

 restricted, on the one hand to a certain vertebrate host (for example, man, the 

 dog, the sparrow), on the other to a certain species of mosquito. It is the full 

 recognition of these facts that has made the thorough investigation of mosqui- 

 toes, systematically and biologically, such an important study. 



In the following, the causative organisms, their life-cycles, and the mosquitoes 

 concerned in each case, are discussed under the heading of the respective diseases. 



EARLY IDEAS. 



The idea that mosquitoes carry disease is not only very old historically, but 

 occurs among primitive nations in various parts of the world. Eeferences have 

 been found in the very early literature of India, in writings that are practically 

 prehistoric, that indicate that the idea was held in those early days, especially 

 with reference to malaria. The natives of different parts of Africa and in Assam 

 are said to hold the same idea, and it has been pointed out that the belief has 

 long been prevalent among the Italian peasants and among those in the southern 

 Tyrol. According to Humboldt the inhabitants of the upper Orinoco at the time 

 of his visit accused the mosquitoes of being the cause of the febrile maladies from 

 which they suffered. Koch points out that the negroes of the Mschamba tribe 

 on Mount Usambara in Africa do not descend into the lower regions on account 

 of fear of fever. Fever in their language is called mhu and mhu is also their 

 name for mosquito, indicating that they understand the connection between the 

 two so perfectly that they have but one name for both. 



Dr. A. F. A. King, of Washington, in an important paper published in 1883, 

 called attention to an article by John Crawford entitled : " Mosquital Origin 

 of Malarial Diseases," said to have been published in the Baltimore Observer in 

 1807, but subsequent investigations by Dr. King and Dr. W. S. Thayer, of 

 Baltimore, have failed to find the article, either in the newspaper itself, or in a 

 review of Crawford's papers published in the Baltimore Medical and Physio- 

 logical Recorder, 1809. 



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