Page 98 - August 2021

EQUINE HEALTH
“There is some belief that the genes associated with abnormal vascular formation may be hereditary, but that is still to be determined.”
PROGNOSIS
“Although we can drain the fluid and save the mare, we haven’t had much success in maintain- ing a viable fetus. Obviously the closer to parturi- tion, the more likely the fetus could potentially survive, but most of the time this problem occurs at eight to nine months of gestation, which is too early for the fetus to be viable,” she says.
“There have been a couple of cases reported that had live foals, but they were cases of hydrops amnios and not hydrops allantois. It is up to the owner to decide whether or not they want to try to save the mare or the foal, but they have to realize that the foal will be very compro- mised at the end of the process,” she explains.
Management of mares early in gestation in which fetal viability is not realistic includes induc- ing parturition. Close monitoring for impending parturition is necessary, since these mares may have poor cervical dilation and very weak uterine contractions, or uterine inertia. Malpositioning and malpresentations of the fetus are also com- mon. In most situations, the fetus cannot be saved, but prompt intervention will give the
Dr. Louise Lemonnier found that 90% of mares survived if the problem was addressed appropriately, and that 95% of those surviving mares
had a future foal.
best prognosis for survival and recovery of the mare, as well as her future fertility. “I do not ever recommend inducing the mare without drainage; usually both the mare and foal die.”
Conservative supportive management of mares with hydrops amnios can result in the birth of a live foal, though it may be deformed. In one report, the mare was monitored for signs of weakness in the prepubic tendon and abdominal wall, while the fetus and placenta were monitored for signs of stress and pending abortion. Anti-inflammatories and altrenogest were administered for pregnancy maintenance. With both hydrops allantois and hydrops amnios there are potential complications of hypovolemic shock and cardiac arrhythmias, or irregular heartbeat, that can be addressed by supportive care such as large-volume IV infusion. When the abdominal wall weakens or there is no viable foal, drainage of fluid and assisted delivery of the foal is necessary.
Horse owners wonder if the mare will be able to have another pregnancy and if it would be normal or not. “There is some belief that the
genes associated with abnormal vascular forma- tion may be hereditary, but that is still to be determined. My advice would be to not breed that mare back to the same stallion, since the problem might be due to the gene combination in that particular mating. Interestingly, there is a new study that was presented at the Society for Theriogenology in July 2021 that looked at 30 mares in a case study and shows that none of them had recurrence of hydrops.” Their subsequent pregnancies were normal.
“Dr. Louise Lemonnier found that 90% of mares survived if the problem was addressed appropriately, and that 95% of those surviving mares had a future foal. The key to success, however, is identifying the problem early and taking the appropriate measures. The good news is that if you identify the signs and treat these mares quickly and appropriately, they have a good survival rate and good future fertility. It’s only when they have ruptured prepubic tendons, abdominal wall tears, hemorrhage or peritonitis that the prognosis is poor,” Wolfsdorf explains.
96 SPEEDHORSE August 2021