Mariano graduated from the National University of Costa Rica in 2011 and worked as a mixed animal veterinarian until 2013, when he moved to Canada to complete a large animal rotating internship at the Ontario Veterinary College, University of Guelph. He then relocated to Auburn University in Alabama (United States), where he completed a residency in large animal internal medicine (equine focused) and a Master of Science investigating the treatment of fungal keratitis in horses.

In 2018, he became a Diplomate of the American College of Veterinary Internal Medicine and remained at Auburn University, first as a clinical lecturer in equine emergency medicine and later, from 2022, as an Assistant Professor in Equine Internal Medicine. In 2023, he earned a PhD in Biomedical Sciences with a focus on regenerative angiogenesis in horses.

His main clinical interests include equine gastrointestinal disease, respiratory disorders, and neonatology, while his research interests broadly centre on clinical pharmacology and the development and application of ex vivo models to advance veterinary medicine.