Our Staff

Ivanov Castellanos

DVM, Practice Owner

Education: National University of Colombia, Iowa State University

Better known as Dr. Ivanov, he finished veterinary school at the National University of Colombia were he also acted as a clinical lecturer for almost four years. In the USA, he went to Iowa State University for additional training and certification and also performed as a clinical instructor for four months.

Dr. Ivanov has an Internship in Medicine and Surgery of small animals from The Ohio State University. He joined Norbeck Animal Clinic as a relief veterinarian in 2004 but soon after, he fell in love with the clientele, the pets and the area, which motivated him to buy the practice in 2007.

Dr. Ivanov still participates actively in academia; he is currently (as of May 2011) an international lecturer for veterinary programs at University of Caldas, in Colombia and on-line lecturer for the Association of Veterinarians Specialized on Small Animals, in Colombia – South America.

Santiago Jimenez Gonzalez


Education: National University of Colombia

Santiago was born in Bogota, Colombia. He studied veterinary medicine at the National University of Colombia, where he met Dr. Ivanov Castellanos as his professor and mentor. When he obtained his degree in 2003, he started working as a zoo vet where he conducted research on large cats including tigers, lions, jaguars, pumas and ocelots. In 2005 Santiago started his PhD in Science working in demographics, genetics and reproduction of jaguars. His dissertation was approved in 2012. He moved to the US in 2009 when he was accepted at the Smithsonian National Zoo where he did his internship in reproduction of clouded leopards. Dr Ivanov invited him to work at Norbeck where he has been part of the staff since 2013. His areas of interest are soft tissue surgery, feline and canine internal medicine and exotics.

David Tuthill


Education: University of Maryland, Virginia-Maryland Regional College of Veterinary Medicine

Dr. Tuthill grew up in College Park, MD, and attended the University of Maryland where he earned his Bachelor’s degree in Biochemistry in 1982. He then attended the Virginia-Maryland Regional College of Veterinary Medicine from 1984-1988, earning his Doctorate in Veterinary Medicine. Dr. Tuthill has devoted much of his professional career to the practice and study of emergency medicine. After a couple years in mixed animal practice, he started working full-time as an emergency vet and found he enjoyed the excitement and challenges of emergency medicine and surgery. During this time he also engaged in research activities with the National Zoo and the National Institutes of Health where he performed laparoscopic artificial insemination of exotic small Asian Leopard Cats for a genetic mapping project. In addition to his many years in both emergency and family veterinary practice, he spent ten years in research and academia: first as a Scientist for the American Red Cross with a special focus on trauma and wound healing; and later as a Biology Professor at Kent State University where he taught microbiology and physiology to nursing and pre-med students. Most recently, Dr. Tuthill owned and operated an emergency hospital in Prince George’s County for 7 years. After closing this clinic, he joined us as a part time relief doctor, and he liked the staff and the clientele so much here at Norbeck that he decided to come on board with us full-time, and we feel lucky to have him. Dr. Tuthill and his wife, Sheila, have 3 boys. His four legged family members consist of an old black Lab named Molly, a Tuxedo cat named Noche, and two guinea pigs, Jasper and Barnaby. His main hobby is music; he plays a little jazz and blues on the piano and guitar.