﻿382 ^^6 Philippine Journal of Science wu 



section of the naturally infected mosquitoes or by experimental 

 infections, to be capable of transmitting malaria. The remaining 

 species either have not been investigated or the evidence of their 

 susceptibility is inconclusive or contradictory. Furthermore, it 

 has been demonstrated that among the anophelines capable of 

 transmitting malaria the different species vary widely in their 

 susceptibility to infection with the malarial parasite and that 

 the same species may not be capable of serving as vector of all 

 three types of human malaria. Finally, it should not be over- 

 looked that the same species of anopheline may vary in its sus- 

 ceptibility to infection with the malarial parasite in different 

 countries or under different ecologic conditions. Such variations 

 have been recorded in the susceptibility of Glossina morsitans 

 to infection with Typanosoma 7'hodesiense' A similar variation 

 in susceptibility may account in part for the contradictory results 

 obtained by different authors in their dissections of, or exper- 

 iments with, certain anopheline mosquitoes. 



These facts and possibilities make it impossible to predict the 

 susceptibility of any species of Anophelinse to infection with the 

 malarial parasite, and render it imperative that every species 

 be tested experimentally in order to be certain of the role played 

 by it in the dissemination of malaria in any country. 



There are two methods of determining the susceptibility of an 

 anopheline mosquito to infection with the malarial parasites. 

 One of these is the dissection of anophelines caught in houses 

 harboring malarial patients, in order to determine the presence 

 of oocysts or sporozoites of the parasites in the mosquitoes : the 

 other consists in experimentally infecting mosquitoes bred from 

 larvae, and afterwards dissecting the mosquitoes for the discovery 

 of the developing parasites, or allowing them to bite healthy 

 persons to prove their ability to transmit the infection. 



It is frequently stated in the literature that such a mosquito 

 has been experimentally infected with malarial parasites but 

 has not been found infected in nature, with the implied conclu- 

 sion that experimental infections furnish a less reliable index 

 of the ability of the species to transmit malaria. However, we 

 believe that the experimental infections, if properly conducted, 

 supply the more reliable index of the relative susceptibility of 

 different species. In mosquitoes examined for natural infection 

 with malarial parasites it is impossible to determine whether or 

 not the mosquito has had an opportunity to bite an infected 

 person, whether or not if the opportunity presented itself it 



'Kinghorn and York, Ann. Trop. Med. & Parasit. (1912), 6, 269-285. 



