CHAPTER XII 



MYXOSPORIDIASIS : SOME OBVIOUS AND SOME 

 CONCEALED DISEASES OF FISHES 



PROTOZOA affect man roughly in three ways. 

 The first means by which their influence is felt 

 is when they attack him direct and produce illness 

 of greater or less severity. The malarial parasites, 

 trypanosomes, and Kala-azar parasites are examples 

 of this class. In the second case the Protozoa may 

 affect transport animals and thereby impede com- 

 merce. The tick belt for the prevention of the spread 

 of cattle ticks and the presence of trypanosome 

 diseases of horses and cattle in Africa are evidence 

 enough in this direction. The third method where- 

 by the influence of protozoal organisms upon the 

 human race is manifested, is when man's food- 

 supply is endangered by the attack of the parasites 

 on food animals. The Piroplasmata of cattle and 

 the Microsporidia of bees seem, perhaps, to be the 

 attackers of the two extremes in the animal kingdom, 

 with fatal results to each. While the protozoal 

 diseases of cattle are extremely important, it must 

 be remembered that they can be controlled to some 

 extent, and hence the danger from the use of con- 



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