INFECTIOUS ANEMIA OF THE HORSE 195 



years (10-15) where annually it causes losses among the 

 horses. 



Etiology.^ — ^Infectious anemia is due to a filtrable virus 

 which cannot be demonstrated by staining methods nor by 

 cultivation. The virus is contained in the blood, urine, and 

 feces of both clinical cases of the disease and apparently 

 healthy horses. According to some authorities the feces, 

 however, will not transmit the disease. It is very probable 

 that the feces are infectious only when mixed with infected 

 urine. 



The disease may be transmitted by virulent blood or urine 

 given intravenously, subcutaneously or orally. Other domes- 

 ticated animals and guinea pigs do not seem susceptible. 



Natural Infection. — ^The disease seems to be taken up 

 through the digestive tract in food, water, stable litter, etc., 

 which have become contaminated with the urine and feces 

 of infected animals. On poorly drained pastm-e fields pools 

 of water may easily become polluted with the discharges of 

 infected horses, especially with urine, thus serving as sources 

 of infection. The disease does not seem to be directly com- 

 municable. Cases are recorded where healthy horses have 

 been confined in stables and mingled freely for months with 

 sick ones without evidence of any transmission of the disease. 

 It is possible that patients are not eliminating the virus 

 continuously and during all stages of the disease. 



Suckling colts are not infected through nm-sing diseased 

 mothers nor has an intra-uterine infection been observed. 



The disease is usually introduced into a community by 

 the purchase of either a clinical case or an apparently healthy 

 horse ("missed case")- 



r Necropsy. — In general the postmortem findings are those 

 of an acute or chronic septicemia. Depending upon the dura- 

 tion of the disease they offer great variations. There are no 

 postmortem changes which can be considered pathogno- 

 monic. The principal changes noted are: Petechise and 

 ecchymoses occurring under the serous membranes especially 

 of the epicardium and endocardium, spleen and bowels; 

 swelling of the lymph glands which are usually blood-shot; 

 changes in the color and structure of the bone marrow 



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