Meet Our Partners

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Our Companion partners came together to further their common goal: to continually improve patient care and client service in veterinary medicine. Cutting-edge technology and ultramodern techniques, while certainly impressive, do not touch on the core of what truly makes a great animal practice. Not to be too wishy-washy, but to provide excellent care for your patients, you also need to provide excellent care for your clients.

The extraordinary doctors listed below have combined their skills and business acumen to promote higher quality in the areas of care and service. By improving these areas, they hope to build closer relationships with their clients and strengthen the bonds between animals and humans.


Dr. Dan Markwalder

Dr. Dan is a graduate of Purdue University School of Veterinary Medicine. He established Animal Care Clinic in Algonquin in March 1994 to provide an environment for high-quality care for his patients.

Dr. Dan has a passion to partner with clients in providing the best care for their pets. He attends over 80 hours of continuing education each year.

Dr. Dan married his college sweetheart; they have four sons and a daughter and a Mini Goldendoodle named Maggie.


Dr. Scott Petereit

Graduating from the University of Illinois College of Veterinary Medicine in 1991, Dr. Petereit brings over 25 years of clinical small animal medical experience to Companion Animal Hospitals. His interests include soft tissue surgery, internal medicine and employing diagnostic modalities such as ultrasound and endoscopy.

Dr. Petereit is a member of the American Animal Hospital Association, the American Veterinary Medical Association, and the Wisconsin Veterinary Medical Association. When he is not helping pets, he spends his time with his wife and three children and the family dog, Tyler. In his free time, he enjoys the remote outdoors, fishing, hiking and snowboarding.


Dr. Joe Whalen

Dr. Whalen is a graduate of the University of Illinois College of Veterinary Medicine. Although he graduated the same year as Drs. Petereit and Markwalder, he’s not sure why they look so much older. His special interests include acupuncture, veterinary chiropractic, rehabilitation and orthopedic surgery.

Dr. Whalen is a member of the American Animal Hospital Association, the American Veterinary Medical Association, and the American Holistic Veterinary Medical Association. He enjoys hanging out with his wife, their dog Sophie, and their two children, Nick and Natalie. His hobbies include running, working out, hiking, fishing, cooking and occasionally playing the guitar.


Dr. Kathy Anderson

Dr. Anderson obtained her DVM from St. George's University in 2005. She has been working as a general practitioner at Norwood Park Animal Hospital since graduation. In 2016, Dr. Anderson purchased the hospital from Dr. Hammer and changed the name of the practice to Companion Animal Hospital of Norridge.

Dr. Anderson has a special interest in Chinese medicine and obtained her acupuncture certification from the Chi Institute in 2009. She is passionate about providing high-quality medicine to her patients and being able to treat them using a combination of Eastern and Western medicine. On her days off, Dr. Anderson keeps busy with her husband Marty and their two children.


Dr. Cheryl Schoessow

Dr. Schoessow attended Rockford College for her undergraduate degree, graduating with a major in biology and minors in both chemistry and psychology. In 2005, she earned her veterinary degree from the University of Illinois. Her desire to be a vet started young at about 4 years old when she went with her mom to take the family dog in for a checkup. She has always enjoyed caring for animals, and after practicing for a while, she realized how much she enjoyed caring for people, too!

Dr. Schoessow has a special interest in imaging, particularly abdominal ultrasound. She has experience in treating exotic pets, too, from her time practicing in a hospital that saw prairie dogs, fennec foxes, serval cats, and even skunks! At home, Dr. Schoessow likes to keep up with family and friends, especially her two children. In her spare time, she enjoys being on the water boating or tubing.


Dr. Jeremy Williams

Dr. Williams attended the University of Illinois for both his undergraduate and veterinary degree. Ever since he was young, he would watch Mutual of Omaha's Wild Kingdom on Sunday mornings. When he and his family moved to the Chicago area, his new neighbor ended up being a veterinarian who would perform at-home veterinary services. The vet let him tag along to appointments, and ever since, he's been hooked on veterinary medicine!

Dr. Williams sees a variety of animals and has a special interest in exotic pets and surgery. Making connections with owners and educating them on their pet's health and husbandry (especially exotic pets) are rewarding experiences as well. When he's not at the clinic, Dr. Williams enjoys watching movies, A LOT! He'll watch just about any genre, including foreign films. He also enjoys exploring the city of Chicago and visiting different neighborhoods when he has the time.


Dr. Derek Williamson

Dr. Williamson obtained his DVM from the University of Wisconsin in 2003. He practiced small animal medicine and surgery for eleven years after graduating at a mixed animal practice in Elkhorn, WI. He always knew he wanted to get into a science-related field, but found the specializations required in human medicine too restrictive. With veterinary medicine, Dr. Williamson enjoys being a surgeon, general practitioner, anesthesiologist, and more—sometimes all in the same day!

Dr. Williamson has a special interest in soft tissue and orthopedic surgery, ultrasonography, and solving complex medical cases. He also finds that interacting with pets and their people on a daily basis is very rewarding. Outside of work, he’s done some pretty incredible things such as summiting Mt. Kilimanjaro with his brother and being an active part of his church’s outreach program in Honduras.


Dr. Amanda Schnitker

Dr. Schnitker graduated from Iowa State University with Honors and then continued her education with two small animal rotating internships: one at the University of Illinois at Champaign-Urbana, and the other at Veterinary Surgical Associates (now Sage Centers) in San Francisco. Since the age of 9, she’s always felt compelled to help animals, so a veterinary career was a chance to do what she loved with her time and talents.

Outside of work, she enjoys gardening, traveling, running, and reading. She and her husband are both adventurers and connoisseurs of interesting foreign foods, too! They love to spend time in different countries to learn more about the people, culture, and food.

Dr. Marrinan

Dr. Mike Marrinan

Dr. Mike Marrinan received his Bachelor of Science and Doctor of Veterinary Medicine degrees from Michigan State University. As a teenager, he wanted to be a veterinarian, stemming from the love and bond that he shared with his childhood dog, Tootsie. Yet, veterinary medicine is a second career for him, as he initially received a business degree and was working in commercial finance. He loves helping animals (and their fur-less family members). Every day is a new adventure and you never know what to expect!

Outside of work, he enjoys all things outdoors (especially fishing, hiking and camping) and spending time with family and good friends.

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Dr. Megan moser

Dr. Moser attended St. George's Veterinary School and settled down after graduation in San Francisco. While there, she worked at a 24-hour emergency hospital and general practices for 12 years. Growing up, she knew she wanted to be involved with animals as much as she could, and as her career evolved as a veterinary technician, she soon realized that she wanted to be even more involved in their health and wellbeing as a veterinarian.

Her special interests include surgery, and she takes great pleasure in solving the most complex cases and providing comfort to both pets and their people. When she’s not at work, Dr. Moser enjoys exploring Chicago’s neighborhoods and the many wonderful restaurants the city has to offer.

Dr. Lin

Dr. Chris Lin

Dr. Chris Lin received his DVM from University of Illinois, Urbana-Champaign – College of Veterinary Medicine in 2015. He received his BA in Economics and minored in Cognitive Science as an undergraduate at University of California, San Diego in 2008. Like many others in veterinary medicine, he has always loved animals and grew up with pets. However, he originally wanted to innovate and introduce technological products that change people’s lives for the better. Over time, he realized that he enjoyed working with his hands and bringing a product from concept to market simply took too long. He was fortunate to have a veterinarian sibling, so he shadowed her to learn what being a veterinarian means. The rest is history.

Dr. Lin loves working with the client and his team and working together to treat the patient. It is important to him to take care of the owner or “pet parent” while helping their beloved family member.

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Dr. Shannon Kofoed

Dr. Shannon Kofoed graduated from University of Illinois Champaign in 2016. After initially starting to work in the veterinary field in 2006, Dr. Kofoed realized her she wanted to become a veterinarian and followed her passion, graduating 10 years later as a DMV with a special interest in veterinary surgery. Her love of animals inspired her to become a veterinarian and she enjoys witnessing the human and animal bond.

Dr. Kofoed grew up in Lake County Illinois and currently calls it home. When she is not practicing high-quality veterinary medicine at Companion Animal Hospital, she enjoys staying healthy and going to the gym.