THE "DUMMY" FOAL
Dr Kirsten Neil BVSc (Hons) MACVSc MS Diplomate ACVIM
Specialist in equine medicine
Goulburn Valley Equine Hospital
Some foals exhibit unusual, bizarre and sometimes entertaining behaviour soon after birth. Signs can range from being slow to latch onto the teat and failing to bond to the mare to aimless wandering, hyperactivity and even seizures. These foals are often referred to as "dummy" foals. Other endearing terms include wanderers and barkers, the latter named after the abnormal vocalization made by some of these foals. Scientific terms include neonatal maladjustment syndrome, hypoxic ischemic encephalopathy (HIE), neonatal encephalopathy and perinatal asphyxia syndrome (PAS). This is a syndrome that encompasses not only the neurological and behavioural manifestations of the disease, but can also involve dysfunction of a number of other organ systems.
Affected foals may appear normal at birth and develop signs within the first few days of life, or they may be affected from birth. In addition to the signs previously mentioned, foals may hang their tongue out the side of the mouth, have difficulty swallowing, not learn to nurse, appear blind, suck on anything, be hyper-responsive to stimuli, be unable to stand or comatose. Foals may also "forget" how to lie down and stand until they collapse from exhaustion. Seizures may be focal such as lip chomping and twitching or the grand-mal seizures similar to the seizure activity we are used to seeing in human epileptic patients.
Signs of other organ dysfunction can include periods of apnea (holding breath), abnormal respiratory rates and patterns, not recognizing the need to urinate (which can result in bladder rupture), and gastrointestinal problems including colic and diarrhea. As you can see, the range of possible clinical signs is broad. However, remember that just because your foal displays one or a combination of the signs mentioned above does not automatically label it as a dummy - other conditions can have similar signs, and more importantly, foals can have more than one disease process going on at once. It is not uncommon for us to see a day old foal that hasn't nursed well if at all, is recumbent and needs assistance to stand, will suck on your arm and has some signs of infection such as pneumonia - these foals often have mild HIE signs, sepsis and by this stage failure of passive transfer as they haven't drunk enough colostrum!
Regardless of the name or term given to the dummy foal, the underlying etiology is thought to be the same - in its most simple terms, a degree of hypoxia or lack of oxygen. This may have been recognized during the foaling process by a long or difficult birth (dystocia), but affected foals can have an apparently normal birth or even a relatively quick foaling. Originally it was thought that the affected foal probably experienced a period of asphyxia during birth, either due to impaired blood flow through the umbilicus or poor perfusion of the uterus and placenta. However the events that lead to hypoxia or poor perfusion can occur before, during, or even immediately after foaling. Pre-partum (before foaling) causes and contributing factors include placentitis (inflammation/infection of the placenta), placental insufficiency (such as with twins - the placenta can't meet the demands of both fetuses), premature placental separation (red bag delivery where the placenta is delivered first before the foal), and disease in the mare such as severe anemia or illness. Intra-partum problems (during foaling) include dystocia, prolonged labour, induced labour, and caesarian section (don't not do a c-section because of this small risk - the aim is to hopefully produce a live foal and mare and the effects of prolonging this procedure can be more devastating). Post foaling respiratory problems or delayed or resuscitation can contribute also.
Whilst a period of hypoxia is implicated in HIE, it is not just the actual lack of oxygen or reduced blood flow (ischemia) that causes the problem. The body can compensate for a lack of oxygen or poor perfusion in the short term by redistributing blood flow to the vital organs - the heart and brain. If the hypoxia continues, this compensatory mechanism starts to fail and circulation to the brain is reduced. Oxygen has a critical role in normal cell and organ metabolism and function with its ultimate role being to supply energy at the cellular level, especially in the brain. A lack of oxygen leads to a lack of energy supply, and a switch to anaerobic metabolism. This in itself can directly affect the cell and lead to oedema, cell death, and ultimately organ compromise or failure. A second wave of cell death occurs when blood flow is restored or the hypoxia is corrected - referred to as ischemia/reperfusion injury. Restoration of blood flow also brings with it potentially damaging mediators including free radicals, degradative enzymes and inflammatory mediators that lead to cell injury and cell death.
The behavioural and neurological signs shown by dummy foals are due to the damage that occurs at the cellular level in the brain. However the effects of a period of hypoxia are not restricted to the brain, with the kidneys and gastrointestinal system also targeted. The most common signs of kidney problems are fluid overload and generalized oedema of the body and reduced urine output. As mentioned earlier, often these foals are not aware that they need to urinate, and bladder rupture can occur. Abnormalities within the gastrointestinal tract can include colic, diarrhea, and some foals do not tolerate feeding and nursing. Foals often have a range of metabolic and endocrine abnormalities including poor regulation of body temperature and blood glucose levels. Blood tests will not identify a foal as a dummy but are recommended for all such affected foals to identify other problems such as sepsis/infection and to establish if the foal has ingested enough colostrum and hence antibodies. Further, some of the pre-partum conditions which can predispose to HIE will be reflected by changes in the blood profile of the new born foal, e.g. foals born from mares with placentitis will often have abnormal white cell count and fibrinogen (acute inflammatory protein) levels
Treatment of dummy foals is heavily reliant on good nursing and supportive care. There is no single injection or treatment that will "fix" the foal. A number of medications are used in an effort to combat oedema and inflammation (DMSO, mannitol) and to provide immediate energy sources for the brain cells or for their anti-oxidant properties (thiamine, magnesium, vitamin E). The mildly affected foal may simply need assistance to stand and nurse from the mare. Some may have no idea how to nurse. Be cautious if bottle feeding these foals - they often do not swallow well and are at high risk of aspirating milk and developing pneumonia. Foals that cannot nurse need urgent veterinary attention - some foals need to be fed via an indwelling stomach tube for the first few days until they are strong enough and have worked out how to nurse. Foals that do not drink enough within the first few hours will often have failure of passive transfer due to lack of colostrum and are at increased risk for infection and sepsis. These foals may require supplementation with colostrum or a plasma transfusion by your veterinarian.
Respiratory support may be needed. These foals may show periods of breath holding and need to be stimulated to breathe. Foals should sit sternally and not be recumbent as this greatly improves their oxygen levels and lung capacity. Some require respiratory stimulants and oxygen therapy. Intravenous fluid therapy may be needed to maintain adequate perfusion and blood pressure. Foals that are not urinating well may need a catheter placed into the bladder to enable continual drainage of urine so that the bladder doesn't become overly full and rupture. Foals may be more tolerant of small frequent feeds and should never be force fed. Seizuring foals need urgent veterinary attention and will often need medications such as valium to control the seizures. If your foal is having a seizure and you are waiting for your veterinarian, try to protect the foal from injuring itself with leg wraps and protective padding. Foals may need antibiotics to treat concurrent diseases such as sepsis or aspiration pneumonia. Foals that are recumbent and lying down a lot need good nursing care and hygiene to prevent pressure sores. Umbilical infections are also more common in recumbent foals. Affected foals should be monitored closely - if in doubt, call your veterinarian.
Management practices during foaling that may reduce the incidence of HIE include foaling observation, assisting delivery of the foal, intra-nasal oxygen and rapid veterinary intervention in difficult foalings. The prognosis for affected foals varies depending on the severity of disease, response to treatment and the development of secondary problems. The survival rate of these foals is generally 70 - 80% with supportive care. The prognosis if often poorer if the foal is also septic, there has been no neurological improvement within 5 days, the foal is comatose and unresponsive or suffers from severe, recurrent seizures. Often by 3-5 days of age you can no longer recognize that there has been a problem, but some foals can take a few weeks before they are normal. Some may continue to be docile or suffer from intermittent seizures. However, many of these foals survive and go on to lead productive and useful athletic lives.
Early recognition, appropriate supportive care and aggressive treatment will influence the outcome for these foals. Uncomplicated cases may resolve spontaneously within a few days if treated appropriately. Consult your veterinarian if you are concerned about your foal - the "dummy" foal can become a completely normal foal and successful athlete.