Persistent Right Aortic Arch, Megaesophagus and Tracheal Stenosis in a White-tailed Deer Newborn (Odocoileus virginianus ustus) at Antisana National Park, Ecuador

Abstract Persistent Right Aortic Arch (PRAA) with retention of the left ductus arteriosus constitutes the most prevalent clinically significant form of vascular ring anomalies in both dogs and cats, accounting for approximately 95% of aortic arch developmental anomalies. This anomaly causes esophageal compression in weaned animals, leading to restricted passage of solid food, postprandial regurgitation, and potential development of acquired megaesophagus. Notably, neonatal, or lactating animals usually do not exhibit these consequences. While PRAA is well-documented in dogs and cats, its occurrence in wild or domesticated ungulates is a rare and intriguing phenomenon, shedding light on congenital cardiovascular anomalies in such species. In this case, a female neonate White-tailed Deer, weighing 2 kg, was delivered to the TUERI Wildlife Hospital at San Francisco de Quito University, Ecuador, following its discovery by tourists in the Antisana National Park. Despite receiving substitute feeding and fluid therapy, the specimen faced challenges in milk transit to the abomasum, resulting in postprandial regurgitation. Imagenologic examinations aimed at elucidating the cause of regurgitation were hindered by forelimbs’ muscle contractions. Nonetheless, these procedures facilitated a presumptive diagnosis of secondary Megaesophagus attributed to a Persistent Right Fourth Aortic Arch (PRAA)., The specimen was euthanized, and the carcass underwent necropsy, revealing a PRAA with distinctive anatomical features, including esophageal dilation, tracheal stenosis, and a constricting vascular ring surrounding both esophagus and trachea. This unique case underscores the importance of considering congenital anomalies in wildlife health assessments and contributes to our understanding of cardiovascular anomalies in wildlife species.