High-Risk Pregnancies and Sick Foals
The January meeting of the Kentucky Thoroughbred Farm Manager's Club featured a topic that many in the room had seen all to much the past two foaling seasons. Fairfield Bain, DVM, Dipl. ACVIM, ACVP, ACVECC, said, "After two years of MRLS (mare reproductive loss syndrome), we all need a break!"
Bain, who is a board certified specialist in internal medicine, pathology, and equine critical care, practices at the Hagyard-Davidson-McGee medicine clinic in Lexington. He remembered when he first came to Kentucky and being astounded by the number of horses in the area. Bain said he remembered another vet saying, "Haven't seen it before? Just wait around a few minutes, you're in Kentucky now." He said it was true that veterinarians see more "unusual" things in Kentucky just because there is such a large population of horses.
In defining a high-risk mare, Bain said she is one which has had previous foaling problems such as dystocia (difficult delivery), hemorrhage, or a red bag delivery. He said a mare also could be at risk because of medical illness, surgery, colic, laminitis, or because she is an older mare. Colic can be related to fetal position, or be a primary GI tract problem. He said pregnant mares which have suffered problems during pregnancy or delivery might have the same problem in subsequent years.
Mares with excessive abdominal size often are suffering from hydrops allantois--hydrops meaning excessive placental fluids. These mares will have huge, pendulous abdomens. He said a uteroplacental fluid transport problem causes build-up of fluids in the allantoic space. "This usually results in termination of the pregnancy to save the mare," said Bain. "We're still trying to design a method of fluid drainage that can allow the mare to maintain the pregnancy."
Premature Mammary Development
Bain said that November, December, and January are peak months for this problem. While mammary development varies from mare to mare, normally two to three weeks prior to the due date the mare will start "bagging up" and her udder will fill.
If the mare shows premature mammary development, it usually is an indication of a placental problem, said Bain. "It amazes me how small an area of inflammation in the placenta can result in this process of early mammary development," he added.
Evaluation of the High-Risk Mare
He said a veterinarian will conduct a physical exam, rectal palpation, speculum examination, and ultrasound exam (both rectal and trans-abdominal). He said during the rectal ultrasound exam, the veterinarian is looking at the cervical region of the placenta in an effort to detect evidence of placental thickening. The transabdominal ultrasound is mainly a fetal biophysical profile.
One of the limitations of prenatal equine care is that it's difficult to predict the time of foaling and to realize when the fetus is in distress. Monitoring is highly dependent on people, he noted. The decision with high-risk mares is whether they can stay at the farm, or if they should be taken to a medical facility, and when that move should take place.
The risks of sending a mare to a medical facility include transportation, the "foreign" atmosphere of the clinic that might distress the mare, and the mare being fearful because she knows something isn't right. Fetal heart rate should be monitored with ultrasound.
Usually seen in geriatric mares, peripartum hemorrhage is when an artery along the uterus ruptures or begins to leak into the abdomen. This can occur prior to foaling, but is more commonly seen afterward. Signs include sudden onset of trembling, varying degrees of colic, profuse sweating, and pale white oral membranes.
Bain said after a diagnosis, his preferred treatment is to put the mare is a quiet, dark stall and leave her alone. She should not be stressed any more than necessary. If the bleeding continues uncontrolled, the mare could go into shock and die. At some point, medical treatment for hemorrhagic shock might become necessary in an effort to save the mare.
Unfortunately, said Bain, there is no surgery today that can be used to save these mares, "but one of these days!" He said some researchers in Germany are looking at endometrial biopsies to try and predict mares which might suffer from hemorrhage.
Bain said he was a little uncomfortable discussing foaling when there were probably more skilled foaling people in the audience than would be gathered together anywhere else in the world. He reminded the audience, however, that a mare with an abnormal labor will get up and down repeatedly and will roll. He said manipulation of the foal on the farm or in the clinic can result in a successful outcome. Sometimes the mare will have to be anesthetized in order to successfully manipulate the foal.
A Caesarian section is sometimes necessary in order to deliver the foal. If the foal is alive, planning ahead and proper organization is needed should the foal require resuscitation. On occasion, this procedure might, unfortunately, need to be a terminal one for the mare due to some catastrophic injury or illness and rapid decision for the procedure required to salvage the foal.
Bain cited the ABCs of resuscitation: Airway, Breathing, and Circulation. He said human research has shown that room air is just as effective during ventilation as oxygen, although it is nice to have oxygen for a distressed foal. He said the key to resuscitation is lung expansion.
"Mouth to nose is probably the best way, even though they're slimy," said Bain, getting a chuckle from the audience. There are other types of resuscitation aids available, but the key in the emergency situation is to make sure that the foal's lungs are being expanded.
Red Bag Presentation
Premature separation of the placenta results in the placenta not tearing to allow the birth of the foal, but rather the intact placenta coming out first with the foal still inside. "This is a critical situation," emphasized Bain. "That foal needs out now!"
However, he said, "not all red bags are created equal." He said with MRLS, it was common to have a red bag presentation. He said the greatest unknown with red bag presentation is that you don't know how long problems existed prior to detection. "That may explain the difference in the outcomes of different red bag foalings," he added.
With MRLS, he said you would see a red bag presentation, and get a weak foal. The signs of illness in the affected foals were basically consistent with a systemic inflammatory response, and there were consistent changes seen on the umbilical cords. Bain showed images of placentas from mares with MRLS, where the discoloration and inflammation of the fetal end of the umbilicus could easily be seen.
The major problem with a red bag delivery is that the foal does not receive oxygen for a period of time. How long that period is will determine if the foal survives, and what condition it will be in if it does live.
Birth asphyxia is caused by oxygen deprivation with blood flow impairment. "It is a common denominator in many foaling problems," he said. This "dummy foal" syndrome is known as hypoxic/ischemic encephalopathy. It has multiple organ involvement, and the clinical signs are due to organ dysfunction, said Bain. When it affects the brain, the foal exhibits sleepiness, abnormal behavior (the "barking" foals), seizures, or coma. If it involves the GI tract, you might see colic or ileus (lack of gut motility). You also can see respiratory problems and general weakness.
"The key point is that this is a biochemical injury that eventually results in organ dysfunction," emphasized Bain. He said there are risks in waiting until a foal involved in a dystocia or red bag delivery shows signs of illness. "That's like watching while Rome burns! We need to do something early on to stop this biochemical injury. Most foals (that suffered from foaling difficulties) will shown problems even if it is three to five days later," said Bain. "This is a major cause of foal death in neonatal intensive care units."
He said recumbent foals require intensive nursing care, including feeding and prevention of secondary problems such as pressure sores and pneumonia.
"Nursing care is the key to survival of the sick neonate," he stressed.
Medical care is focused on blocking the biochemical injury. This might include treatment with magnesium (which might help block damage to nerve cells), drugs from human stroke treatment, anti-seizure medications, DMSO and mannitol to help reduce edema, and antioxidants such as vitamins C and E.
"Future efforts will be on early identification of risk factors for birth asphyxia, treating foals before signs occur in at-risk foals, and the use of antioxidants," said Bain.
One of the new therapies that is being used at the medicine clinic is hyperbaric oxygen therapy. This is exposure to 100% oxygen at greater than one atmosphere, he explained. This treatment is most often used for decompression sickness--when deep-sea divers get the "bends" from surfacing too quickly and suffering from a gas bubbles forming in the blood stream and obstructing blood flow.
"We're trying to get more oxygen to the cells and to the injured tissues," said Bain. "Hyperbaric therapy is an adjunctive therapy (adjunctive meaning in addition to other medical therapy) for asphyxial injuries and other problems, such as bone infections. It helps in tissue salvage for wounds, and for brain and spinal trauma cases.
As Bain said earlier, there is a problem with trying to determine whether a foal is physically ready to be born. Most other species, he explained, are ready to be born long before birth; a horse is only ready two to three days before birth. That profoundly affects decisions on what to do with a compromised pregnancy, he said. "There is a difference in viability versus athletic ability," said Bain, explaining that while in human medicine it is enough to save the baby, in equine medicine, the athletic ability of that foal sometimes must be taken into account.
Interestingly enough, Bain said that in utero infections seem to improve the viability of foals which have not reached gestational maturity. There seems to be something about placental infection that hastens the maturity process of the fetus.
"Orthopedic issues remain a big hurdle for the premature foal," said Bain. "You can have crushing of the immature cuboidal bones in the hocks (and other problems with a skeleton that isn't mature enough to stand up to the foal's weight)."
He emphasized the importance of colostrum not only for the antibody protection it offers the newborn, but because "it does things we don't yet understand," said Bain. He said plasma therapy for neonatal foals is popular, with the main reason for that treatment the failure of passive transfer of colostral antibodies.
The question of when to treat a foal for low levels of IgG (antibodies) has long been debated, noted Bain. He said 400 is probably okay, but if you have a sick foal, you should try and get the numbers higher, to at least 800.
There also are some foals being treated with disease-specific plasma or hyperimmune plasma in an effort to prevent disease later in life, such as pneumonia from the Rhodococcus equi bacteria.
An immune condition sometimes seen is titled jaundiced foals (also known as neonatal isoerythrolysis or NI). This disease occurs when the antibodies from the mare's colostrum destroy the foal's red blood cells because the foal inherited the stallion's red blood cell type (which was different from that of the mare).
"The foal may be breathing hard due to decreased oxygen-carrying capacity," said Bain. "His membranes may be varying degrees of yellow depending on the timeframe and severity of the problem. You need to identify at-risk mares with NI screening and have an alternate colostrum source. You also have to muzzle the foal to prevent him from ingesting the mare's colostrum.
"When can the foal nurse?" questioned Bain. Typically, one to two days is sufficient to milk out a mare and provide an alternate colostrum and milk source to the foal.
If the foal suffers from NI, he might have to have a blood transfusion. Bain said there is a new product that eliminates the need to search around frantically for either a universal donor or take the time to transfuse the foal from his dam's blood. The product is called Oxyglobin (Biopure Corporation). "This is a polymerized bovine hemoglobin," explained Bain. "It doesn't damage the kidneys, has a long shelf life, and no refrigeration is needed." He said he thinks this product will have widespread human use in the future, and is already being used in military settings. He said the drawback is that it is expensive; however, the initial investment might be offset by reduced length of illness and a shorter hospital stay.
Unusual Immune Problems
Other immune-mediated conditions that are occasionally seen in foals can include immune-mediated thrombocytopenia and neutropenia. "Thrombocytopenia" means a low blood platelet count, which can result in hemorrhages in the first few days of life. Immune-mediated neutropenia is when a foal has a low white blood cell count because of antibodies that are destroying the white cells called neutrophils.
"The biggest issue is differentiating this from a septic foal or a herpes foal," said Bain. "These (neutropenia cases) are clinically normal foals, and they recover on their own in a few days."
Bain reminded the audience that checking the placenta is necessary because "it is part of the fetus." He stressed it should be looked at carefully for meconium staining (an indicator of oxygen deprivation, which could mean a high risk foal for pneumonia and other problems), and missing pieces of placenta, which if retained could be disastrous for the mare.
The Race for Education
The Farm Managers Club makes a donation to a charity of the speaker's choice as a "thank you." Bain is on the Board of Directors for a newly formed group called The Race for Education. This group is working to provide educational opportunities to families of workers on the horse farms and at the racetracks; increase awareness of careers within the industry; and attract better-educated and more qualified individuals to the industry.
He said the group wants to introduce racing to a younger group of individuals through a positive program based on education, and begin to develop fans of the future. The contact person for the Race For Education is Elisabeth Jensen, P.O. Box 2093, Lexington, Ky. 40588; 859/252-8648. The office is located in Dudley Square in downtown Lexington.
About the Author
Kimberly S. Brown was the Publisher/Editor of The Horse: Your Guide To Equine Health Care from June 2008 to March 2010, and she served in various positions at Blood-Horse Publications since 1980.
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