OUR VETERINARIANS
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Bret Peterson, DVM
Owner and Veterinarian
Dr. Bret Peterson grew up near Chicago, which is when he developed his love for the Chicago Cubs. He earned his Bachelor's in Biology from Knox College and his doctorate of veterinary medicine from Iowa State University. Dr. Peterson worked as a small animal veterinarian and surgeon in Wisconsin before relocating to Springfield and becoming the owner of Laketown Animal Hospital in 2018. He has a special interest in soft tissue and orthopedic surgery, along with internal medicine, and he takes great pride in building a staff who is passionate about what they do. During his free time he enjoys woodworking and spending time with his wife and daughter. They especially enjoy beach days where they can rediscover the simple pleasures through their daughter's eyes such as building sandcastles and playing in the waves. They recently adopted a kitten, named Meowy.
Aaron Felgenhauer, DVM
Associate Veterinarian
Dr. Aaron Felgenhauer (Fell-ghen-how-er) joined the Laketown veterinary staff in 2018. Originally from central Illinois, Dr. Felgenhauer earned his BS and DVM degrees from the University of Illinois. He has a special interest in internal medicine and nutrition. When he isn't working, Dr. Felgenhauer enjoys spending time with his family, especially his daughter. He also loves traveling, playing sports, and watching sports. A few of his favorite teams are the St. Louis Cardinals, Green Bay Packers, and the Fighting Illini.
Susan Fisherkeller, DVM
Associate Veterinarian
Dr. Susan Fisherkeller was born and raised in Springfield and is proud to have spent her life getting to know the ins and outs of the capital of Illinois. She graduated with her Bachelor's in Biology and her doctorate of veterinary medicine from the University of Illinois. Dr. Fisherkeller loves kayaking, traveling (especially to Europe), and has a special interest in pairing wines with different cuisines. She is extremely close with her friends and as she likes to say, the "young-ins" who work with her. Dr. Fisherkeller has opened her home to many rescue dogs in the past, with Sam being the most recent.
Cassie Vespa, DVM
Associate Veterinarian
Dr. Vespa, originally from Springfield, IL, has always felt a deep connection to animals. Growing up surrounded by a variety of pets, she found herself more at home with animals than people. Her strong bond with her cat, Tiger, who was her companion from age 10 to 30, inspired her to pursue a career in veterinary medicine and become an advocate for the voiceless.
Dr. Vespa’s educational journey began at Saint Louis University, where she majored in Nutrition and Dietetics with a focus on culinary arts. Initially planning to attend medical school for humans, she ultimately decided to follow her passion for animals and switched her path to veterinary medicine. She went on to attend the University of Illinois College of Veterinary Medicine, where she also served as the manager of the Wildlife Medical Clinic.
After earning her veterinary degree, Dr. Vespa worked for two years at a small animal practice in Boulder, CO, further honing her skills and gaining experience in diverse aspects of veterinary care. Her professional interests include wildlife, zoo species, conservation, pain management, and dentistry.
In her free time, Dr. Vespa enjoys outdoor activities like walking and hiking, as well as cooking, baking, crafting, and relaxing. She loves spending time with her husband, playing video games, and attending comedy shows.
At home, Dr. Vespa shares her life with her 5-year-old dog, Shiya, and her 7-month-old kitten, Poppy. Her favorite travel destination is the Caribbean, though she dreams of exploring Europe in the future.
Dr. Vespa is passionate about helping animals and looks forward to continuing her journey in veterinary medicine, advocating for the well-being of all creatures, big and small.
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Lauren Steininger, DVM
Associate Veterinarian
Dr. Steininger is originally from Petersburg, Illinois, and her passion for animals began at a very young age—by the time she was four or five, she already knew she wanted to become a veterinarian. That dream led her to Southern Illinois University Carbondale, where she attended on a local agricultural scholarship and earned her degree in Animal Science with a pre-veterinary focus and an emphasis in equine science.
From there, she was accepted into the veterinary program through Colorado State University in partnership with the University of Alaska Fairbanks. She was honored to be part of the second class of ten students to complete the first two years of the program in Fairbanks. The experience was incredibly hands-on—they had unique opportunities to work with musk oxen and reindeer, and Dr. Steininger particularly loved working with sled dogs. After two years in Alaska, she finished her clinical training at CSU and graduated in 2020, right at the height of the COVID-19 pandemic.
Although her professional work since graduation has primarily been in small animal medicine, Dr. Steininger has a deep-rooted love for livestock—especially horses and sheep. After vet school, Dr. Steininger returned to Alaska for a few years, which gave her even more opportunities to work with sled dogs and enjoy the outdoors.
Outside of work, Dr. Steininger enjoy spending time in nature—hiking, fishing, camping, and riding her horse. At home, she shares her life with a lively crew that includes a horse, two dogs (one of whom is her three-legged wonder, Winnie), a flock of chickens, a fluffle of rabbits, and some fish.
Alaska remains one of her favorite places in the world. Even after living there for over four years, there’s still so much to explore—and she and her family always look forward to returning to visit the friends and landscapes they love.
Phillip Gillen, DVM
Associate Veterinarian
Dr. Gillen is originally from the Decatur area and grew up in Warrensburg, Illinois. His early years were spent next door to his grandparents’ farm, where he was constantly surrounded by animals—livestock, chickens, sheep, hogs, cows, dogs, and cats. That environment had a lasting impact on him, and even though his family later moved closer to Decatur, his connection to animals remained strong.
Dr. Gillen began his college journey at Millikin University, studying pre-med for two years before transferring to the University of Illinois at Urbana-Champaign. There, he completed a year of undergraduate work in Animal Science before earning his Doctor of Veterinary Medicine in 1980. It was during that final year of vet school that Dr. Gillen met his wife, who was completing her degree in Animal Health Technology.
While Dr. Gillen had dreams of becoming an astronaut during junior high, a pivotal moment changed his path: his family had to put their dog to sleep when he was in 8th grade. That experience led Dr. Gillen to pursue veterinary medicine, where he has since developed special interests in dermatology, gastroenterology, endocrinology, and internal medicine—especially in small animal care.
Dr. Gillen practiced for many years at Lincoln Animal Hospital in Lincoln, Illinois, and after selling the practice, he officially retired in 2021. In 2022, he and his wife moved to Chatham to be closer to two of their children’s families. Dr. Gillen returned to veterinary practice part-time in the fall of 2024.
Outside of work, Dr. Gillen enjoys reading, movies, biking, flying radio-controlled airplanes, and playing pickleball. Family is very important to Dr. Gillen—he and his wife have four children and eleven grandchildren, and they look forward to their annual summer trip with whomever can make it. While they used to have multiple pets, Dr. Gillen currently has only one dog at home. Losing their beloved golden retriever to cancer last year led his wife to insist: one dog at a time!
Dr. Gillen and his wife enjoy occasional travel within the U.S., especially to national parks and scenic destinations.