THE PROTOZOAN SUBGROUPS 349 



will be influenced by climatic conditions. If the larval 'ticks are already 

 present and at once attach to the exposed animals symptoms of the fever 

 may develop ten to twelve days later. Where the susceptible animals 

 are placed upon pastures, in pens, or other places immediately after 

 these have been infected with ticks from southern cattle, a period must 

 intervene covering egg-laying and hatching of the larvae before the 

 northern animals become inoculated. In summer this period may oc- 

 cupy from twenty to forty days; in cooler weather it takes longer for the 

 eggs to hatch, and under such conditions sixty days or longer may be 

 required before the infective generation of ticks appears. Thus, de- 

 pending upon season and temperature, the disease may appear in twelve 

 days to two or three months after exposure (see life history of Texas 

 fever tick, page 148). 



Sjmiptoms. — Two distinct types of Texas fever are presented, — an 

 acute fatal and a chronic form, from the latter of which the animals 

 usually recover. Whether the fatal or the milder type appears will de- 

 pend upon season and the susceptibilty of the animals. When northern 

 cattle and those raised in tick-free districts in the South are attacked in 

 the hot weather of summer, the acute form occurs. If the susceptible 

 animals are affected in the latter part of autumn the milder chronic sym- 

 ptoms appear, and it is by this type of the disease that partly immune 

 southern cattle are affected at any season, the fatal form rarely attack- 

 ing these animals. 



The Acute Tjrpe. — In this form of the disease the onset of the symp- 

 toms is rapid. The animal is depressed and stands or lies down apart 

 from the herd, there is loss of appetite and rumination ceases. The tem- 

 perature rises within twenty-four to forty-eight hours to 107° or 108° F., 

 the fever accompanied by increase in the rate of pulse and respiration. 

 During the early stages of the disease there is constipation which 

 is generally followed by diarrhea. The hemoglobin released by the 

 disintegration of the corpuscles causes a blood-stained urine (hemoglobi- 

 nurea), from which symptom is derived the name "red water," some- 

 times given to the disease. Cerebral disturbances, exhibited by stag- 

 gering, disorders of- vision, or delirimn, may appear in some cases. A 

 conclusive diagnosis may be made upon finding the parasites within the 

 corpuscles by microscopic examination of the blood. 



A fatal termination is usually reached within three or four days. If 

 recovery occurs, it is much prolonged, due to the time required for the 

 generation of new corpuscular elements to replace those destroyed. 



The Chronic Type. — The difference in the symptoms of the chronic 

 type of the disease from those of the acute is one of degree. Further, 

 there is a seasonal difference, the milder chronic form usually appearing 

 in the late fall and early winter, the acute in the hot summer months. 

 The temperature does not go as high, remaining at about 103° F. and 



