Prepping for Foaling Season
By Sally Silverman
It’s spring. Daffodils, red-wing blackbirds and foals are arriving. In their first few weeks of life, foals are gangly newborns and highly susceptible to illnesses. At New Bolton Center clinicians are investigating diagnostic and treatment options for sick foals.
Gastrointestinal disease is common in equine neonates, and necrotizing gastrointestinal disease, where a portion of the gastrointestinal tissue actually dies, can be fatal. One study focuses on the usefulness of abdominal ultrasonography in the assessment of these conditions. “It’s a serious and poorly understood disease,” says Dr. Cristobal Navas de Solis, LV, DACVIM. “The human counterpart of this disease, necrotizing enterocolitis (NEC), is the most common GI complication of premature babies.”
The results of the first part of the study, by Drs. Navas, Palmer, Boston and Reef, were recently published in the Equine Veterinary Journal, 44. For this study, records of foals seven days or younger with signs of gastrointestinal disease were studied. Abnormalities in all parts of the gastrointestinal tract and abdominal viscera were found in the sonograms, supporting the importance of performing comprehensive abdominal ultrasound exams in this group. In some of the foals gas was seen in the bowel wall reflecting a necrotizing disease. This was the first such report of the sonographic detection of gas in the bowel wall, and the evaluation of its prognostic value in neonatal foals. The investigators were encouraged by the results.
The objective of the current project is to prospectively describe the appearance of the gastrointestinal tract in ultrasound examinations of normal foals and foals with gastrointestinal disease seven days of age and younger. Normal ultrasound characteristics of the gastrointestinal tract have been previously obtained in adult horses and ponies; however a similar study has not been performed in foals. In horses, as in other species, the wall of the gastrointestinal tract is thinner and has a different appearance in young animals when compared to adults. Understanding the sonographic appearance of the gastrointestinal tract in normal foals will assist in evaluating ill foals in clinical practice. The bowel can change in thickness, contents, and appearance of its four main layers, or have abnormal blood flow. All of these characteristics can potentially be evaluated in a sonogram.
The data is being gathered from normal, healthy foals and those that are ill. Michelle Abraham BVMS is scanning the abdomens of healthy foals at three local farms. Dr. Navas is scanning abdomens of sick foals in the New Bolton Center Neonatal Intensive Care Unit (NICU). When compilation of the data is complete, they will be compared. The New Bolton Center clinicians hope that the knowledge gained will help identify early changes resulting from disease, and that that information can be used to guide the treatment before the disease becomes severe.
Dr. Abraham says that this project is a solid example of the positive results of collaborative efforts. “We are gaining information from the farms that are allowing us to scan their foals, and hopefully the results of the studies will help those farms and their local veterinarians. As an internal medicine resident, I am gaining information from our own NICU and, analyzing that information alongside the information from the farms will help all of us develop protocols for early diagnosis and treatment of NICU patients.” Dr. Navas says that much of what is already known about necrotizing GI disease comes from human medicine; it is difficult, however, to apply that knowledge directly to foals. “We are hoping to learn the specific characteristics of GI disease in foals. The diseases between the two species are similar in many aspects, and what is learned through the equine research could impact the human side of this illness someday.”
Another recent project, led by Melissa MacKinnon DVM, investigated the causes, management and outcomes of foals admitted to the hospital with signs of colic. The study included 137 foals thirty days or younger admitted between 2000 and 2010 with signs of colic. Most were treated medically with intravenous fluids and supportive care. Signs of colic in such young foals can be very subtle, particularly if the foal has a concurrent disease process. Many of those with more severe, constant pain were diagnosed with small intestinal strangulating obstruction (SISO), such as an intestinal twist, evidence of which can also be seen on a sonographic exam. SISO was the most common reason for surgery in the neonates. The overall short-term survival rates for foals undergoing colic surgery was comparable to those managed medically for non-surgical causes of colic. “The decision to perform colic surgery in neonates,” concluded Dr. MacKinnon, “should not be negatively influenced by their young age. Long-term survival was good and neonates surviving to maturity were likely to be used as intended.” The study highlighted the importance of recognizing foals with a SISO early so that the obstruction to the blood supply can be corrected quickly with surgery.