60 THE EEPOET OF THE No. 36 



Insects as Essential Hosts of Pathogenic Okganisms. 



Beyond the mere statemenf that a number of tapeworms undergo their sexual 

 stage in some insect or other Arthropod, and that of these at least two are occasional 

 parasites of man, while others commonly affect domestic animals, it may be well 

 to point out that one of these species, Hymenolepis diminuata, living comnionl; 

 in the intestines of rats and mice, has as its alternate host certain insects which 

 feed in meal, and that man may become infected by eating the dejecta of such 

 insects in dirty cereals. 



It should also be stated in passing that several nematode worms have this 

 dual relation. Sir Patrick Manson's discovery of the carriage of Filaria iiodurna 

 by Culex fatigans, thus producing filariasis, is exemplified most terribly by cer- 

 tain forms of elephantiasis. Further, recently Dr. Eansom, of Washington, has 

 shown- that a common nematode parasite of the house fly. known as Hahronema 

 muscce, is, in another stage, a stomach parasite of the horse, and that 

 the- embryos produced by the parent worms in the stomach of the horse pass out 

 with the fseces and enter- the bodies of fly larvte, which are developing in the 

 manure. Infested flies, dead or alive, are accidently swallowed by horses, and 

 the parasite completes its development to maturity in the stomach of this defini- 

 tive host. , 



There is still another nematode which may be mentioned on account of the 

 fact that it brings in an entirely new type of insect host, namely Echinorhynchus 

 gigas, a common parasite of the pig, and reported as occurring in man. In Europe 

 the usual intermediate hosts are the larvse of the cockchafer, and in the United 

 States the common white grub or larva of the so-called June-bug. 



Mosquitoes and malaria. (Discussion and lantern slides). 



Mosquitoes and yellow fever. (Discussion and lantern slides). 



Insects and try pano so myiasis. The curious, flagellate protozoa known as Try- 

 panosomes are coming more and more to the front as causative organisms of various 

 diseases, especially in the tropics. It is one of these organisms which causes, the 

 nagana of African cattle, and is carried hy the tsetse fly known as Glossina morsi- 

 ians. As noted above, this insect is not only a direct inoculator of the disease, but 

 is an essential host .of the parasite. Sir David Bruce, of England, discovered the 

 causative organism, and established the fact of its transfer by tsetse flies, but it 

 was a German observer, Kleine, who demonstrated in 1909, that a part of the life 

 cycle of the parasite takes place in the fly, which becomes infective again after ten 

 days, and able to transmit the disease for weeks thereafter. 



Another trypanosome disease which has become famous is the one which 

 causes the sleeping sickness of Africa, and of this disease the tsetse fly Glossina 

 palpalis is the necessary secondary host. This disease is said to have caused thirty 

 thousand deaths between 1902 and 1905, in the British Province Bugosa on the 

 Victoria ISTyanza. 



Down in Brazil it has been quite recently discovered that a disease known as 

 Opilagao. a wasting disease of children, is caused by Trypanosoma cruzii, and that 

 the definitive host of this organism is one of the la'rge biting true bugs known as 

 Conorhinus megistus, a close relative to the so-called giant bedbug of this country. 

 Conorhimis sanguisuga. This discovery by Chagas, of the Oswaldo Cruz Institute, 

 was considered so important that another learned member of the Institute, Arturo 

 Neiva, visited the United States and Europe just before the war, in order to mono- 

 graph competently the biting bugs of this group. 



Insects and Leishmanioses. The Leishmania organisms are intracellular 



