MALIGNANT HEAD CATARRH OF THE OX 403 



resistance of the body tissues, especially mucous meinbranes, 

 through toxins which it eliminates. The ulcers and pseudo- 

 membranes may be due to secondary invading bacteria. 



Natural Infection. — ^The mode of infection is not yet under- 

 stood. Probably the germs harbored in damp, dirty stables 

 contaminate the food and water and thus are talcen in through 

 the digestive tract. Occasionally the disease appears among 

 cattle on pasture, but usually only when the available drinking 

 water is foul. 



The disease has not been transmitted by inoculation. It 

 does not spread by contact. Tn some stables, as noted, it 

 exists for years, appearing each spring and fall and in time 

 causing considerable losses. 



Young, fat cattle (one to three year old steers) are most 

 often attacked. One attack does not produce immunity 

 against subsequent ones. A given animal may suffer suc- 

 cessive attacks a few weeks or months apart. 



Symptoms. — ^The period of incubation is from twelve hours 

 to two days. 



The disease usually begins with symptoms of fever (104° to 

 107° F.). The surface temperature is unevenly distributed, 

 the poll of the head hot, the muzzle hot and dry. The fever 

 drops on the second or third day. Before death it becomes 

 subnormal. 



Nervous Symptoms. — ^The head is held low or rests on the 

 manger. In some patients on the second or third day there 

 is marked stupor, the animal lying on the ground unconscious. 



In other patients there is excitement, the animal bellowing, 

 rearing, and plunging. Locomotion is difficult, the gait 

 uncertain and staggering. Twitching of the muscles of the 

 neck, shoulders and body may occur. Epileptiform spasms 

 have been observed. The excitability of the patient is 

 increased by such external influences as bright sunlight, 

 sudden noise, etc. 



The eyes on the first or second day show conjunctivitis, 

 which may extend to the cornea causing keratitis. There are 

 photophobia and profuse lacrimosis. The cornea becomes 

 turbid or "milky," the clouding beginning at the periphery. 

 Iritis and cyclitis are also observed, the anterior chamber 



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