During the peak of the Covid-19 pandemic, Dr. Lily Parkinson, an emergency and critical care veterinarian at the University of Georgia, found herself responding to urgent calls about snow leopards. The coronavirus had spread to various zoo animals, but snow leopards, in particular, were experiencing severe illness, including critical anemia—a dangerous shortage of red blood cells leading to oxygen deprivation.
For humans or even common pets, a red blood cell transfusion would be a standard procedure, readily available from an established blood bank. However, no such resource existed for snow leopards or other exotic animals, and veterinary knowledge regarding blood types and compatibility in these species was extremely limited.
Zoos quickly mobilised, with those housing healthy snow leopards offering to sedate their animals, collect blood, and ship it to Dr. Parkinson. This was especially critical as she was already immersed in a research project on blood typing in large, wild cats. Yet, the logistical hurdles proved immense, and often impossible to overcome. Zoo staff, essential for blood collection, were sidelined by illness. Precious samples were lost in transit. As Dr. Parkinson recalled, “Other zoos that really wanted to donate and help were just not able to drop everything that they already had on their schedule.”
Tragically, many leopards deteriorated so rapidly that euthanasia became necessary before any transfusions could be arranged.
Today, Dr. Parkinson, now a clinical veterinarian at Brookfield Zoo Chicago, is taking proactive steps to create a vital resource that could have saved those animals: a dedicated blood bank for zoos and aquariums. This pioneering initiative aims to stock a diverse array of prescreened blood from exotic species.
Her vision relies on advanced techniques used in human medicine that enable the delicate preservation of red blood cells, kept on ice for many years. If this method can be successfully adapted for creatures ranging from polar bears and pangolins to dolphins and dik-diks, it would dramatically enhance zoos’ preparedness for future animal health crises. “We could theoretically try to bank every animal that we have in zoos and have it frozen and ready,” she explained.
The Challenge of a Short Shelf Life
Blood, regardless of whether it comes from a human or an animal, comprises several components. These include red blood cells, vital for transporting oxygen throughout the body, and plasma, the liquid matrix in which these cells are suspended. Many zoos already collect and store plasma, which freezes easily and is rich in nutrients, antibodies, and other essential proteins. Plasma transfusions are, for instance, sometimes used to support newborn giraffes that haven’t received sufficient critical antibodies from their mothers.
However, animals suffering from severe infections, chronic illnesses, or massive blood loss frequently require transfusions of red blood cells. The main challenge? Red blood cells have a frustrating tendency to rupture when frozen and subsequently thawed.
In human medicine, freezing red blood cells is reserved for specific, limited scenarios, such as preserving very rare blood types or ensuring a stable supply for combat zones. This freezing process, which can extend cell viability for a decade or more, is inherently complex, expensive, and labor-intensive. Consequently, human blood banks, which experience rapid turnover of supplies, typically opt to refrigerate red blood cells, granting them a shelf life of approximately six weeks. Unfortunately, as Dr. Parkinson noted, “that just doesn’t fit the timeline of what you need in a zoo.”
Zoos perform transfusions infrequently, and the characteristics of red blood cells vary dramatically across the animal kingdom. “Every animal seems to have its own unique type of red blood cell, and then many different types of blood types as well,” Dr. Parkinson explained. Maintaining a refrigerated blood bank would necessitate constant collection from dozens of species, much of which would likely be discarded unused.
Dr. Parkinson is currently engaged in collecting as much blood as possible, often coinciding with the routine wellness exams performed on the animals at Brookfield Zoo Chicago.
Last year, Dr. Parkinson secured a grant from the American Association of Zoo Veterinarians to explore the feasibility of freezing red blood cells from a wide range of exotic species.
“It’s a technology that’s in human medicine but really kind of forward-thinking in terms of veterinary medicine,” commented Dr. Taylor Yaw, Vice President of Science and Animal Health at the Henry Doorly Zoo and Aquarium in Omaha, which is contributing elephant blood to the initiative. “Can we freeze these red blood cells, cryopreserve them, and then basically wake them up at a future date?”
The Deep Freeze
With funding now secured, Dr. Parkinson’s immediate goal is to collect as many blood samples as possible. She achieves this efficiently by coordinating with the regular wellness exams of animals at Brookfield Zoo Chicago. For instance, on a recent Friday morning, River, an 8-year-old clouded leopard, underwent a comprehensive checkup. The veterinary team first sedated the big cat, then performed a thorough head-to-tail examination including a dental check, CT scan, and ultrasound. Following this, approximately a quarter cup of her blood was carefully drawn and handed over to Dr. Parkinson.
Dr. Parkinson then processes the blood: she spins it in a centrifuge to isolate the red blood cells from the plasma. A glycerol solution is then slowly introduced, crucial for protecting the cells during the freezing process. The prepared sample is then added to a growing frozen collection that already includes red blood cells from gorillas, bottlenose dolphins, orangutans, a polar bear, an emu, and even a pangolin.
Simply acquiring these samples has been a remarkable achievement, demanding both patience and ingenious solutions. For example, Dr. Parkinson had to specially assemble tiny, 20-ml blood bags – which she affectionately calls “adorable” – for smaller donors like koalas, pangolins, and dik-diks, a small, cat-sized antelope native to Africa.
Dr. Parkinson also receives samples from partner institutions, including beluga whale blood from the Shedd Aquarium in Chicago, elephant blood from the Henry Doorly Zoo and Aquarium in Omaha, and giraffe blood from the Cheyenne Mountain Zoo in Colorado Springs.
The Cheyenne Mountain Zoo, a leader in animal care, had previously established a national plasma bank for giraffes. They’ve successfully trained some of their giraffes to voluntarily cooperate with blood draws, eliminating the need for sedation. “We’ve got giraffes that will stay for upward of 20 minutes and allow us to draw plasma,” shared Amy Schilz, a senior animal behaviorist at the zoo’s giraffe center. As a sweet reward for their cooperation, the giraffes receive rye-crisp crackers, “which is essentially like giving them a candy bar,” Ms. Schilz added.
Having previously collaborated with Dr. Parkinson on a giraffe plasma study, Ms. Schilz eagerly supported the expansion of this work to red blood cells. “I’m all in,” Ms. Schilz affirmed. “Just tell me what you need, and we’re going to go get it.”
The Great Thaw
The true test of this innovative endeavor will commence once the blood cells have been stored on ice for a full six months. At that critical juncture, Dr. Parkinson will carefully thaw each sample, meticulously wash away the glycerol solution, and then, as she describes it, “compare it to how happy it was before I froze it.”
Her assessment will involve several key factors: she’ll determine the percentage of cells that survived the freezing process intact, observe their appearance under a microscope for any abnormalities, and verify if they remain metabolically active, among other detailed evaluations. Additionally, she will determine if the cells can withstand automated washing by specialized machines or if they require the far more labor-intensive process of being handled manually.
Initial findings are quite encouraging: red blood cells harvested from giraffes and elephants, Dr. Parkinson reports, “do not appear to mind being frozen.”
This particular success holds immense promise for elephants, a species highly susceptible to a virus that can induce fatal internal bleeding. Cryopreservation could revolutionize their care by allowing zoos to store an elephant calf’s own blood at birth, then later transfuse it back to them should the need arise. “They could donate their own blood to themselves,” Dr. Parkinson highlighted.
However, initial experiments with polar bear and emu blood proved less favorable, Dr. Parkinson admitted. She noted that these tests involved only small quantities of blood, suggesting that adjusting the thawing protocol might yield better results.
While the research remains in its nascent stages, Dr. Parkinson harbors a hopeful vision for the future. She anticipates a time when zoos facing critically ill lions, lemurs, or leopards can fully dedicate their efforts to patient care, unburdened by the daunting task of sourcing exotic animal blood. “You can just focus on the ill animal,” she concluded, “and then maybe we can have a central blood bank that worries about all the other stuff for you.”