Everyone at Tillema Veterinary Clinic takes pride in their work. We love animals and use our knowledge and compassion in the treatment of every patient we see. Helping your pet live a happy and healthy life is why we come to work each day so we welcome you to stop and see what we have to offer.


Dr. Tillema, DVM

Dr. Tillema grew up on a dairy in a small town in West Texas. Dr. Tillema served in the United States Navy and then when his tour ended, he began his studies to become a veterinarian where he worked three jobs and went to school. Dr. Tillema began practicing veterinarian medicine in upstate N.Y. where his patients were big and small. He soon moved to California where he opened his own mixed practice as a mobile unit. Seeing that he was limited on what he could do for his small animal clients, Dr. Tillema opened a small animal practice in Corona. Dr. Tillema was injured by a bull and acupuncture was the only pain of relief that he had, after that incident Dr. Tillema studied acupuncture at the Chi Institute where he found that Western and Eastern medicine worked better together than any one alone. Dr.Tillema also has an interest in orthopedic medicine as well as general practice. When the Doctor isn’t working he enjoys skydiving, zip-lining, hiking, fishing, barbeques and watching and playing sports.

Dr. Olmstead, DVM

Dr. Olmstead is our relief veterinarian here at Tillema Veterinary Clinic. She graduated from Ross University in 2006, and then went on to do a year internship with Willamette Valley Equine where she was hired on as an associate. With her specialty being equine, she is a very valuable addition to our practice. She likes to spend her free time with her three horses and two dogs. 

Maria, RVT

Maria graduated from Mt. San Antonio College with an Associate of Science Degree in Animal Health Technology. She has been a licensed Registered Veterinary Technician for 20 years. She has practiced in a variety of fields ranging from small animal hospitals to research and development. Prior to joining the Tillema Veterinary Clinic team, she worked for 12 years at an emergency and critical care facility. She has a large and varied family of pets in her household including dogs, cats, tortoises, rabbits, a chinchilla, a bird and a frog. Maria enjoys attending karate tournaments with her husband, son and daughter as well as collecting succulents and cacti and photography.

Jenn, Veterinary Assistant

Jenn graduated from Carrington College with an Associates of Science in Veterinary Technology in 2017. She has been involved in the equine industry for over 10 years and has shown on the breed show level and open circuit as a youth rider resulting in multiple year-end championships and circuit awards. She has two BLM mustangs, one of which she competed with in the 2009 Extreme Mustang Makeover in Norco winning 10th overall.  Jenn shares her life with her husband, five miniature dachshunds(yes, FIVE!), two horses, two goats, and a mini horse. In her spare time, she enjoys crossfit, running, and hiking.

Jenelle, Veterinary Assistant

Jenelle is in her second year at Cal Poly Pomona where she is studying pre-veterinary/animal science. Jenelle is working toward becoming a mixed animal practice veterinarian. When she is not studying or working at a diary, Jenelle likes to hang out with her three dogs, three cats, and two birds as well as hiking and being outdoors. 

Karina, Veterinary Assistant

Bio coming soon!

Brandi, Client Care Specialist

Brandi is another one of our very versatile team members.  She is helpful in many areas of the hospital, but is especially supportive of our clients at the front desk.  Ever since she was a little girl she always wanted to work with animals. It brings her joy to be able to do what she does here at the clinic and looks forward to coming to work every day! When Brandi is not at work she enjoys being outdoors and spending time with family, friends and her daughter.  Brandi also has four-legged babies.  She has two young dogs, and both are very hyper.  Her female pup is a pit bull and her male pup is a very cute husky.  Both are rescue dogs.  

LesLee, Practice Manager

LesLee McDowell was born in Nebraska and raised throughout the Midwest in states such as Kansas and South Dakota. Everywhere LesLee lived she has always be a big part of a local 4-H club as well as FFA. LesLee's love for animals started at a very young age and she has owned many different animals throughout the years such as horses, goats, Corriente roping steers, cats, dogs, quail and even some pheasant. Her passion however was definitely always horses.  Her entire life she has competitively shown horses at many different levels and in many different events, such as halter, western pleasure, trail and even some pony and cart classes. One of her most memorable classes was a pony and cart event she competed in with her Shetland Pony Floyd, whom her dad had trained. LesLee’s herd has since shrunk considerably down leaving her with two great dogs named Roxy and Harley and one very supportive husband John.