CHAPTER XII. 



TROPICAIi DISEASES. 



SURRA. 



This disease is caused by the Trypanasoma Evansi, an organ- 

 ism which is a low form of animal life and is fonnd in the 

 blood of afl'ected animals. It attacks and destro3's the red 

 blood cells, causing rapid loss of flesh and, sooner or later, 

 death. It is claimed by some authorities that the disease 

 originates from the use of w^ater and grass from low^ lands. 



Symptoms. — Variable temperature, ranging from normal 

 to 102° and even to 106° F. ; dullness; lack of vigor; sometimes 

 swelling of the submaxillary lymph glands ; thin, watery dis- 

 charge from the nostrils ; swelling of the sheath and legs, more 

 frequently the hind ones (Plate XIX), and swelling along the 

 belly; these swellings pit on pressure. The mucous membrane 

 of the eye, especially of the haw^, shows dark-red spots 

 (petechial spots) ; the urine is highly colored and is usually 

 passed in large quantities; the bowels are constipated in the 

 early stage, and profuse diarrhea occurs later. In chronic 

 cases paralysis of the hind extremities takes place, the animal 

 staggering when moved. The paralysis may later become com- 

 plete and the horse will be unable to rise. In the acute type of 

 the disease the animal dies in twelve or fifteen days, while in 

 the chronic case he may linger for one or two months. The 

 diagnosis is complete only when a microscopic examination of 

 the blood discloses the parasite (Plate XX). As a rule, the 

 parasite is seen only when the temperature is considerably 

 elevated. 



Surra is ahvays fatal, and as the danger to other animals is 

 great on account of its highly contagious nature, all animals 

 that have been proved to have the parasite in the blood should 

 be removed at once from contact with healthy stock and 

 destroyed. The carcasses should be saturated with oil and 

 l)urned. Measures to prevent the spread of the disease should 

 ahvays be enforced. "When in a district infested with siirra 

 the temperature of horses should be taken regularly every 



(102) 



