How Brookfield Zoo Chicago is exploring the possibility of the world’s first frozen red blood cell bank for zoo and aquarium animals
Have you ever gotten your blood drawn at a doctor’s appointment, or even donated your blood? Maybe you learned a little bit about your blood: what type it is, some information on your red and white blood cells, or, if you donated it, what it might be used for. For humans, the process of donating, storing, and transfusing blood from one to another has saved countless lives in medical emergencies. Today, the procedure is routine.
In zoos, aquariums, and even the wild, animals also need blood rushed to them in an emergency. Scaly and dangerously trafficked pangolins, giraffe calves in need of antibodies, elephants at risk for disease — for all kinds of species in and out of professional care, blood in an emergency could save not only their lives, but their population.
But where humans can rely on blood banks, which follow established and timely procedures, getting an animal the blood it needs is a race against the clock. Each animal species has unique blood, and identifying blood compatibility and transporting donor blood in time to save a life is often difficult or impossible with limited information.
At Brookfield Zoo Chicago, clinical veterinarian Dr. Lily Parkinson is searching for a solution. And no one is better suited for the job: she is currently the only zoo veterinarian in the country who specializes in both zoo medicine and emergency and critical care medicine. This is why she’s working to create the first long-term frozen red blood cell bank for zoo and aquarium animals.
Studying Animal Blood Types
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When Dr. Parkinson was working on plasma transfusion and crossmatching projects for giraffes and elephants, she didn’t know the moment would define her upcoming research. When performing this research, Dr. Parkinson really wanted to be able to store the plasma and red blood cells to continue studying these blood components beyond the first day of the research.
Blood is made up of red and white blood cells, platelets, and plasma, a mix of proteins and liquid. Plasma storage and transfusions, even in animals, are more well established because plasma freezes well, unlike red blood cells. This is because red blood cells can’t even go in a freezer as they will burst. They can go in the fridge, but they have to be used within 30 to 42 days. Red blood cells can be particularly impactful in emergency situations, such as a traumatic injury or previously undetected illness. Because those situations aren't as frequent, zoos and aquariums typically can’t use the blood cells within that 30-day refrigeration timeframe.
But when Parkinson experimented on leftover giraffe red blood cells during the course of her original projects, she discovered she could stabilize them with a solution — making it possible to freeze red blood cells and save them for a later date. This changed the game. She began to ask herself what other animal red blood cells could also freeze without bursting under these conditions.
“What studies that came before this — mainly dogs and cats — show us is that every type of blood reacts differently to getting frozen,” said Parkinson. “Which is why it is so important to do this study.” So began her 2024 experiment of freezing and thawing different animal blood types, supported by the American Association of Zoo Veterinarians’ Wild Animal Health Fund and the Chicago Board of Trade Endangered Species Fund (CBOT). At the end of the project, Parkinson will know whether or not a bank of animal red blood cells is even possible.
“When all is said and done, I won’t be surprised if the study says, yes, this is going to work for giraffes and elephants and polar bears, but it isn’t going to work for emus, for example,” Parkinson explained. “That’s why we have to include as many animals in this project as possible.”
Crossmatching Across Zoos
Koala, bottlenose dolphin, polar bear, brown bear, pangolin, emu, orangutan, gorilla, giraffe, elephant — in the Zoo’s state-of-the-art animal hospital, these are just some of the nearly 15 species with blood bags of varying sizes stacked in the hospital’s negative 80-degree freezer. The freezer is divided into multiple sections, maintaining the temperature when the doors are opened. More species are added every month!
At Brookfield Zoo Chicago, when an animal undergoes a preventative medical screening or health assessment, the veterinary team may collect a blood sample. Just like when you have blood drawn, we can use this blood to better understand an individual animal’s medical history. And where possible, trained vets also collect blood for Parkinson’s blood bank.
Parkinson takes each of these samples and separates red blood cells from plasma through centrifugation and then slowly adding a specialized solution to allow red blood cells to freeze. Once she freezes the blood, though, it’s not automatically ready for transportation and transfusion. The tricky part comes when it’s time to thaw the red blood cells and see how well each species’ blood held up under freezer conditions. (Think of it like a tub of chili you froze last winter. As you’re thawing it to reuse this fall, did freezer burn impact its composition or does it taste as it did several months ago? Have all the ingredients maintained their structure?)
But for well-preserved red blood cells to even be useful, other zoos and aquariums would have to be a part of the project. Maybe you know your blood type and who you could donate to. Even if you don’t, a doctor will test blood compatibility on a patient before a transfusion using a well-established understanding of how human blood works. The same can’t be said of animals around the world and in the wild. Their blood types are completely different from human blood, and for each species, there’s no promise that blood will be compatible between, say, one tiger to another tiger. In order to identify compatible pairings, Parkinson needs to “crossmatch” the blood samples from partners around the country.
Thankfully, facilities like Cheyenne Mountain Zoo and Omaha’s Henry Doorly Zoo and Aquarium are supporting the project. As both zoos train some of their animals in voluntary blood collection, developing a better understanding of blood compatibility for beloved giraffes or juvenile elephants is a key piece of their care and health approaches. This vested interest spurred the beginnings of the project.
Cheyenne Mountain Zoo’s International Center for the Care and Conservation of Giraffes also runs workshops to help other zoos train their giraffes to give blood. This broadens the scope of Parkinson’s research — the more samples she has to work with, the more crossmatching data we have identifying which giraffes across the country can donate to each other. "We were thrilled to offer our knowledge in voluntary blood draw training, and our network of giraffe care professionals to support this effort led by Dr. Lily," said Amy Schilz, senior animal behaviorist at the International Center for the Care and Conservation of Giraffe. "When we all share our expertise, knowledge and networks, we can do so much more for giraffe everywhere, and this is a perfect example of that."
Omaha’s Henry Doorly Zoo and Aquarium invited Parkinson to join them in creating a crossmatching database specifically for elephant calves. For elephants, this effort could make all the difference as they struggle against the threat of EEHV (or elephant endotheliotropic herpesvirus) Hemorrhagic Disease (EEHV-HD). This disease often causes fatal hemorrhaging, and as such, is a leading cause of death in young elephants around the world. Parkinson’s blood bank could be lifechanging in an emergency, as EEHV-HD progresses rapidly. “The health and wellbeing of the elephants in our care, and all elephants, is critical,” said Dr. Taylor Yaw, vice president of science and animal health at Henry Doorly. “Partners like Dr. Parkinson allow us to break down barriers in preventative medicine and provide exemplary, life-saving health care to animals when it matters most.”
The good news is that both these partnerships have led to results: Parkinson has successfully thawed both giraffe and elephant red blood cells from the bank! This means that we now know it’s possible to store those animals’ blood in a freezer bank. “I’m very hopeful that there will at least be some species that will be perfect for a frozen red blood cell bank,” she said.
With many more species to go, though, more zoos have promised to send samples to Brookfield Zoo Chicago.
Happy, Healthy Red Blood Cells
Though Parkinson has many more details to work out, this progress has already opened doors we previously didn’t know we could open. “I just really love when the red blood cells come out of the freezer and they’re happy and healthy after being frozen for a month,” she said. “We didn’t know that was possible before we started this project.”
So once the red blood cells come out of the freezer happy and healthy for a species, what next? Depending on access to technology and different facilities’ capabilities, the dream is for Brookfield Zoo Chicago to become a national hub for gathering, processing, and distributing blood needed in emergencies. Parkinson and the Zoo’s veterinary experts could also help train veterinarians around the country to create and run their own blood banks from east to west with geographically significant centers.
This would also put Brookfield Zoo Chicago at the forefront of elephant care in preparation for their return as part of the Zoo’s Next Century Plan, unveiled in 2024. Caring for elephants requires clear emergency plans and resources in case of EEHV-HD. With an established blood bank, Brookfield Zoo Chicago could provide emergency care for elephants here and at zoos around the country, quickly shipping frozen blood to veterinarians concerned about the onset of disease. Parkinson’s research could also support ongoing efforts to develop a treatment for EEHV-HD, a process that would be less demanding with easier access to elephant blood. For example, elephants could receive transfusions of their own blood from the bank instead of relying on other elephants.
Happy, healthy red blood cells aren’t just the key to Parkinson’s research — they're also key to innovative animal veterinary medicine and care. As we look to the future of Brookfield Zoo Chicago and our wildlife partners, research paves the way for the ongoing care and protection of species around the globe, in this century and the next.