CHAPTER XXII 



TEXAS FEVER, CONTAGIOUS ABORTION, AND 

 FOOT-AM) MOUTH DISEASE 



Communicable discuses of both man and the lower ani- 

 mals are caused not only by microorganisms usually classed 

 as plants, but by microscopic animals, the protozoa. Ma- 

 hiria and sleeping-sickness are among the important human 

 diseases caused by protozoa, and Texas fever is the most 

 important protozoal animal diseasr. 



The pathogenic protozoa may be found in the intestines, 

 and are then eliminated in the feces, from which there is 

 opportunity for them to find, their way into the bodies of 

 healthy animals. Another class of protozoa are to be found 

 in the blood, and are transmitted from one animal to an- 

 other by biting insects. The anopheles mosquito is re- 

 sponsible for the transmission of the malarial organism, and 

 one of the cattle ticks for the transmission of the Texas 

 fever organism. In the case of diseases transmitted by in- 

 sects, there is opportunity for widespread distribution, 

 while in the case of the diseases caused by intestinal forms, 

 the chance of the organism gaining entrance to the tissues of 

 a susceptible host is much smaller. The fight against the 

 spread of the insect-borne protozoal diseases is a fight 

 against the transmitting insect, the tick in the case of Texas 



fever. 



Texas fever. The parasite is found in the red blood- 

 ceils, which are destroyed by it, and the red coloring mat- 

 ter, the hemoglobin, is set free to be eliminated from the 

 body in the urine, to which it imparts a red or black color. 



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