INFECTIOUS ABORTION OF MARES 477 



jennets. The bacillus belongs to Subgroup II of the colon 

 typhoid group and has been named the Bacillus abortivo- 

 equinus. 



Natural Infection. — The disease is usually introduced by 

 an infected mare whose discharges pollute food, especially 

 grass. The disease therefore spreads readily among mares 

 on pasture, especially where an aborted mare has soiled the 

 grass with fetal membranes and discharges. The part played 

 by the stallion as a transmitter is a matter of dispute. Ob- 

 viously intermediary agents, such as grooming utensils, 

 blankets, harness, etc., may carry the infection. 



S3rmptoms. — The period of incubation is about two weeks. 

 The symptoms of the disease are in general similar to those 

 in the cow. During the early stages of pregnancy they may 

 pass unnoticed, as the small fetus, dropped on the pasture, 

 may not be found. Even in the advanced stages the first 

 symptom noticed is usually the aborted dead fetus. In some 

 mares, in. the latter stages of gestation, restlessness and 

 colicky pains occur. As the fetus is not usually fully de- 

 veloped, it is expelled easily and as in normal parturition. 

 Occasionally, however, probably due to the weakened con- 

 dition of the mare, the last stage of parturition is not com- 

 pleted and the fetus is found lodged in the os uteri and vagina. 

 In a large stud a few mares will show symptoms follow- 

 ing abortion, such as fever, marked depression and vaginal 

 discharge. 



The aborted fetus and the fetal membranes usually present 

 pathological lesions. A peculiar "sour" odor emanates from 

 the placenta, and also from the stomach contents of the fetus. 

 The fetal ovaries (testes) are much enlarged, the lungs often 

 hepatized, spleen swollen, the mesenteric lymph glands 

 congested, and petechiee occur on the serous membranes. 

 Small abscesses may invade the myocardium. 



Following the abortion, and often prior to it, a chocolate 

 colored, fetid discharge from the vagina is noted. Retention 

 of the afterbirth is a common sequel, in some cases leading to 

 peritonitis and septicemia. Mares do not usually abort 

 several times in succession. As a rule, a live foal is delivered 

 the following year. 



Digitized by Microsoft® 



