presence of Ehrlichia riticii in the lymphoid tissue along with colitis. The mare is also predisposed to retaining fetal membranes often leading to the development of endotoxemia & laminitis.
Bacterial Metritis and Placentitis
Abortion associated with bacterial metritis and placentitis is usually caused by ascending bacterial infection from the . The most common pathogens are Streptococcus spp., Salmonella spp., E. coli, pseudomonas spp., Klebsiella spp., Staphylococcus spp., Actinobacillus spp., and Nocardia spp. Infection of the uterus and the placenta cause placentitis and metritis, which triggers an immune response from the mare that results in abortion at about 6-8 months. In most cases the bacteria cross the placenta to enter the fetus causing autolysis of fetal tissue. The aborted fetus is severely or mummified, there is edema of the placenta, and there is fibronecrotic exudate from the fetus, the placenta and the uterus. In most cases there is retardation of fetal growth as the fetus may have died weeks before being aborted.
Fungal Causes
Equine Mycotic Placentitis
Abortion associated with equine Mycotic placentitis is caused by ascending infection from the vagina. Infection is caused by Aspergillus spp., Mucor spp. or Candida spp. The fungus grows in the surface of the placenta and passes hyphae through the placenta into the fetal fluids and eventually into fetal circulation. Placentitis triggers an immune response that results in abortion of the fetus. Abortion occurs late in gestation and is accompanied by a thickened chorioallantoic membrane and the finding of exudate within the placenta. The aborted fetus is fresh and shows growth retardation and dermatitis. Necropsy reveals that the liver is pale and elongated, and that fungal hyphae are present in the placenta as well as the fetal lungs, liver or stomach.
Disorders Related to Pregnancy
Uterine Torsion
Uterine torsion is considered rare in mares but may be caused by violent
of the
mare or an over-active fetus.
The motion of the mare rolling causes the uterus to twist, crossing the ligaments. One broad ligament passes dorsal to the uterus while the other one lies ventral to the uterus. This can affect blood supply to the uterus resulting in hypoxia and ischemic necrosis. Displacement of the ovaries may accompany uterine torsion in some cases, but the positioning
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