88 INFECTIOUS AND PARASITIC DISEASES. 



Most of these have as yet a circumscribed distribution, 

 so that the diseases which they cause are hmited to 

 certain regions. Examples of such diseases are parasitic 

 haemoptysis (pulmonary distomiasis), which is found 

 almost exclusively in China, Japan, and Formosa; 

 bilharziosis (endemic or Egyptian haematuria), pre- 

 vailing particularly in Egypt, North Africa, Arabia and 

 Persia; hook-worm disease (ankylostomiasis, uncin- 

 ariasis), common in Porto Rica, Southern United States, 

 the Philippine Islands and Egypt ; guinea- worm disease 

 (dracontiasis), occurring principally in Africa, East 

 Indies, and Panama. These examples suffice to show 

 the relationship between insects and disease on the one 

 hand, and regions and insects, upon the other. It is 

 because the physical characteristics in so large a measure 

 determine the insect and animal life of a country that 

 we include them among the predisposing causes of 

 disease. 



In tropical and sub-tropical countries many more 

 diseases are due to animal infectious agents, and animal 

 parasites, than in temperate latitudes, and larger 

 numbers of both agents are transmitted by insects. 

 This fact again emphasizes the danger to the peoples 

 of temperate climates in that either pathogenic parasites 

 themselves, or their insect-hosts, may be imported dur- 

 ing the period of greatest heat and moisture, find the 

 conditions propitious for multiplication, and sow their 

 virus promiscuously. Moreover, a few may become 



