CONTROL OF FLUKE DISEASES BY DESTRUCTION OF 

 THE INTERMEDIATE HOST 1 



By Asa C. Chandler 



Instructor in Biology, Rice Institute, Houston, Tex.; formerly Assistant Professor of 



in Zoology and Physiology, Oregon Agricultural College and Experiment Station 



Flukes have long been known as causative agents of disease in ani- 

 mals, especially sheep; in fact the loss resulting from their ravages in 

 some sheep-raising countries can be estimated in millions of dollars an- 

 nually. Within comparatively recent years flukes have been discovered 

 to play an important role in some countries in the production of human 

 disease. At present human fluke infections are known to be more or 

 less prevalent in nearly all tropical and subtropical countries and in 

 some countries of temperate climate. The blood flukes, Schistosoma, 

 occur in the oriental countries and throughout most of Africa and trop- 

 ical America. Human liver flukes, Clonorchis, and the lung flukes, 

 Paragonimus, are primarily diseases of the Orient, but epidemic cases 

 have been reported from other countries. The various species of intes- 

 tinal flukes which are habitual or accidental human parasites occur in 

 both Asia and Africa and probably in other tropical countries, but these 

 are of minor importance. 



The important relation of fluke infections to the public health in en- 

 demic countries is not generally realized. In Egypt, for instance, over 

 half the population is said to suffer from schistosomiasis, and in an ex- 

 amination of 54 boys in the village of El Marg, near Cairo, Leiper {id) 2 

 found 49 to be infected. Cawston (j) states that in some districts in 

 South Africa 80 per cent of the school boys and 10 per cent of the girls 

 are infected and that Schistosoma infections seriously retard both the 

 physical and mental development of the school children. Troops oper- 

 ating in endemic regions are much affected by the disease unless strin- 

 gent preventive measures are taken. The British army suffered severely 

 in the Boer war, and in 1914 the British Government was still under 

 heavy expense for pensions for soldiers invalided by schistosomiasis. 

 Laning, of the United States Navy, states that it is not uncommon for 

 large proportions of the crews of patrol gunboats operating on the Yangtze 

 River to be completely disabled by Schistosoma japonicum infections. 

 Nakagawa (13) states that lung flukes are harbored by as high as 50 per 

 cent of the population in some districts in Formosa, and in parts of 

 Japan the infection is hardly less prevalent. Clonorchis, a human liver 



1 Contribution from the Zoological Laboratory, Oregon Agricultural Experiment Station, Corvallis, 

 Oreg., and from the Biological Laboratory, Rice Institute, Houston, Tex. 



2 Reference is made by number (italic) to "Literature cited," p. 208. 



Journal of Agricultural Research, Vol. XX, No. 3 



Washington, D. C Nov. 1, 1920 



vi Key No. Oreg.~5 



(193) 

 9507°— 20 3 



