860 Infectious Anemia of Horses. 



several months; not infrequently however it may even extend 

 over several years (Marek). 



Course and Prognosis. The acute form of the disease 

 usually leads to a gradual aggravation of the symptoms, death 

 ensuing without any struggle. Sometimes however it passes 

 into a chronic form. Death may occur unexpectedly in the 

 acute as well as in the chronic forms. The chronic form de- 

 velops from the acute, with a gradual diminution of the severe 

 general symptoms, or the disease may have developed from 

 the beginning with a chronic character, when periodical im- 

 provements or aggravations of varying duration may be ob- 

 served. The fatal termination results either after the develop- 

 ment of the cachectic condition or because the disease assumes 

 an acute course. 



Recovery is observed only exceptionally (Carre & Vallee, 

 Ostertag, Marek). One should not be deceived by the some- 

 times very lasting improvement in the chronic form, as later 

 a relapse, or a progressive anemia with emaciation usually 

 occurs. 



In a large stud in Hungary with a great number of horses, in which the 

 disease prevailed for five years, there were several horses which originally were 

 affected visibly, but for several years had showed no symptoms whatsoever, but . 

 even in those rare cases recovery occurred only in a clinical sense, as in one case 

 blood from one of the apparently recovered animals proved infectious (Marek). 

 A similar occurrence had previously been observed by Carr§ & Valine. 



The epidemiology of the disease varies greatly with the 

 duration of the individual cases. Usually, in connection with 

 the introduction of new horses, only isolated affections occur 

 at first, the disease taking a rapid course from its onset, while 

 in very chronic cases the disease is only recognized when a 

 large number of the horses have already become infected and 

 affected because the symptoms are for a long time very obscure. 

 If in such cases no preventive measures are introduced, their 

 number increases from week to week and the animals become 

 attacked without reference to age or breed. In stables how- 

 ever, which have been infected for a long time, the newly in- 

 troduced animals become affected first and most severely. For 

 this reason the disease is usually acute in newly , infected 

 stables (Carre & Vallee). At the same time animals in other 

 stables, or of the same stable kept in other pastures and 

 watered in separate places, remain temporarily free from the 

 disease at times even for several years. 



In a stud in Hungary the disease did not appear among foals, which had been 

 kept in an isolated stable or on a separate pasture, until four years after 

 apparently recovered mares had been placed among them. 



Diagnosis. In infected localities or in infected stables, the 

 clinical symptoms, the course of the disease, and the negative 



