§54 Infectious Anemia of Horses. 



ing an intermediate action by any parasitic insects. Contrary 

 to this Ries asserts that the infection is transmitted by the 

 larvae of gad-flies or mosquitoes. He failed however to sub- 

 stantiate his contention by experimental proof. 



Infection only results when either large quantities of viru- 

 lent material are taken at one time, or from the taking of smaller 

 quantities at frequent times. Accordingly the occasional in- 

 gestion of a mouthful of contaminated hay or straw does not 

 appear at all dangerous (Ostertag). 



Whether the affection which sometimes occurs in the suck- 

 ing foals of affected mares, results from an intrauterine con- 

 tamination or an infection through the milk cannot be decided. 



The introduction of the disease in previously uninfected 

 premises invariably occurs through newly bought, affected or 

 apparently recovered horses, whose blood however continues to 

 retain its infectiousness (Marek). As long remissions are by 

 no means rare in the chronic forms of the disease, and as in 

 the cases of slow course only very few apparent s;sanptoms 

 are generally noticeable, it happens not infrequently that liorses 

 suffering with the disease are offered for sale. 



Anatomical Changes. The infectious anemia of horses is 

 characterized by the anatomical changes of an acute or chronic 

 septicemia, with visible changes of the blood, in wdiich the 

 changes depending on the duration of the disease may show 

 very pronounced variations. 



The spleen in acute cases, or in animals Avhich have died 

 during a relapse of the disease, appears considerably enlarged, 

 sometimes double or four times its size. Its capsule is tense 

 and covered with hemorrhages, the pulp is blackish-red, dis- 

 tended, mushy, sometimes even liquefied, as in anthrax. Some- 

 times in the otherwise normal or more or less enlarged spleen, 

 various sized nodulated protuberances are found, which repre- 

 sent softened areas of a blackish-red color. The slower the 

 course the less marked is, as a rule, the swelling of the spleen, 

 while in a very protracted course it may be entirely absent, 

 but in such cases the consistency of the organ is rather some- 

 what increased. All of the lymph glands of the body show 

 acute swelling and a hemorrhagic condition is noted in cases 

 in which hemorrhages have occurred in the corresponding 

 organs; in chronic cases however the hanph glands either fail 

 to show an edematous swelling or it is but slight. Subserous 

 hemorrhages are usually found. In chronic cases however 

 they are not prominent. Hemorrhagic ppots up to the size 

 of a silver dollar are especially numerous under the peri- 

 toneum of the cecum and colon, they occur also, but in 

 smaller numbers in other parts of the peritoneum. A yel- 

 lowish or reddish serous fluid may be present in small quan- 

 tity in the abdominal cavities. Usually numerous hemorrhagic 

 spots are seen in acute cases under the capsule of the more 



