Just a few years ago, amidst the height 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 begun to affect various zoo animals, but these majestic snow leopards were particularly vulnerable, developing severe anemia—a critical shortage of red blood cells that deprived their bodies of oxygen.
For humans, or even common pets like cats, such a condition would typically be managed with a straightforward red blood cell transfusion, readily available from an established blood bank. However, the world of exotic animals presented a stark contrast.
There were no specialized blood banks for snow leopards, and veterinary knowledge on blood types and compatibility in wild species was extremely limited. Zoos across the country frantically searched for compatible donors. Those fortunate enough to house healthy snow leopards offered to sedate their animals for blood draws, then rush the samples to Dr. Parkinson, who, by chance, was already researching blood types in large wild cats.
Yet, the logistical hurdles were immense, often proving insurmountable. Key zoo staff were out sick, vital samples were lost in transit, and as Dr. Parkinson noted, “Other zoos that really wanted to donate and help were just not able to drop everything that they already had on their schedule.”
Tragically, some leopards succumbed to their rapidly deteriorating health and had to be euthanized before a life-saving transfusion could even be arranged.
Today, Dr. Parkinson, now a clinical veterinarian at Brookfield Zoo Chicago, is on a mission to prevent such outcomes. She’s pioneering the creation of a groundbreaking resource: a comprehensive blood bank specifically for zoos and aquariums, meticulously stocked with prescreened blood from a diverse array of exotic animals.
Her innovative approach draws from advanced techniques in human medicine that allow fragile red blood cells to be preserved on ice for years. If she can successfully adapt this method for everything from polar bears and pangolins to dolphins and dik-diks, it would revolutionize emergency preparedness for animal health worldwide. “We could theoretically try to bank every animal that we have in zoos and have it frozen and ready,” she said.
The Unique Challenges of Animal Blood Storage
Blood, whether from a human or an animal, comprises several distinct elements, including red blood cells, which transport oxygen throughout the body, and plasma, the fluid in which these cells are suspended. Many zoos already collect and bank plasma, a component that freezes easily and is rich in nutrients, antibodies, and essential proteins. Plasma transfusions are sometimes administered to treat newborn giraffes, who often struggle to acquire vital antibodies from their mothers.
However, animals suffering from various infectious or chronic illnesses, or those experiencing significant blood loss, often require transfusions of red blood cells. These cells, unfortunately, have a problematic tendency to burst when subjected to freezing and thawing processes.
In human medicine, red blood cells are frozen in specific, limited scenarios—for example, to store exceptionally rare blood types or to guarantee a stable blood supply in active combat zones. Yet, this freezing process, which can preserve cells for a decade or more, is inherently complex, costly, and labor-intensive. Consequently, human blood banks, which rapidly cycle through their inventory, typically refrigerate red blood cells, giving them a brief shelf life of roughly six weeks. Dr. Parkinson points out that this short lifespan simply “doesn’t fit the timeline of what you need in a zoo.”
Zoos perform transfusions infrequently, and the red blood cells themselves exhibit an enormous variety 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. Establishing a refrigerated blood bank would necessitate constant blood collection from dozens of diverse species, much of which would likely expire before it could ever be utilized.
Last year, Dr. Parkinson successfully secured a grant from the American Association of Zoo Veterinarians to delve into the feasibility of freezing red blood cells from a diverse array of exotic species.
“It’s a technology that’s in human medicine but really kind of forward-thinking in terms of veterinary medicine,” explained Dr. Taylor Yaw, vice president of science and animal health at the Henry Doorly Zoo and Aquarium in Omaha, a key partner providing elephant blood for the project. “Can we freeze these red blood cells, cryopreserve them, and then basically wake them up at a future date?”
Pioneering Cryopreservation for Diverse Species
Now, with funding secured, Dr. Parkinson is actively working to “collect as much blood as I can,” she stated, strategically aligning her efforts with the routine wellness exams already scheduled for animals at Brookfield Zoo Chicago. One Friday morning last month, River, an 8-year-old clouded leopard, underwent a comprehensive checkup. The veterinary team gently sedated the feline, performing a thorough head-to-tail examination including dental, CT scans, and ultrasound. Following this, approximately a quarter-cup of her blood was carefully drawn and handed over to Dr. Parkinson.
Dr. Parkinson then processed the blood, spinning it in a centrifuge to separate the red blood cells from the plasma. A glycerol solution was incrementally added to safeguard the cells during the freezing process. The prepared sample was then placed in a specialized freezer, joining a rapidly expanding collection of red blood cells from a captivating assortment of animals, including gorillas, bottlenose dolphins, orangutans, a polar bear, an emu, and even a pangolin.
The act of simply gathering these samples has been an achievement in itself, demanding both patience and ingenious solutions. For instance, Dr. Parkinson had to meticulously assemble tiny, 20-ml blood bags—which she affectionately calls “adorable”—to accommodate smaller donors such as koalas, pangolins, and dik-diks, cat-sized antelopes native to Africa.
Dr. Parkinson’s collection efforts extend beyond Brookfield Zoo Chicago. She is also acquiring samples from various other institutions: 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, which previously played a role in establishing a national plasma bank for giraffes, has even trained some of its animals 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 delightful incentive for their cooperation, the giraffes are rewarded with rye-crisp crackers, which Ms. Schilz likened to “giving them a candy bar.”
Having previously assisted Dr. Parkinson in a study focused on giraffe plasma, Ms. Schilz expressed her unwavering support for this expanded initiative to bank red blood cells. “I’m all in,” Ms. Schilz enthusiastically declared. “Just tell me what you need, and we’re going to go get it.”
The Moment of Truth: Thawing and Testing
The true test of this pioneering work will unfold after the collected cells have spent a minimum of six months in deep freeze. At that crucial juncture, Dr. Parkinson will meticulously thaw each sample, carefully rinsing 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 scrutinizing several key indicators: the percentage of cells that remain intact, their appearance under a microscope, and crucially, whether they retain metabolic activity. She will also determine if the cells can withstand automated washing by a machine, or if the more labor-intensive manual processing is necessary.
Initial findings are quite encouraging, with early results indicating that red blood cells derived from giraffes and elephants do not “appear to mind being frozen,” according to Dr. Parkinson.
This discovery opens up particularly exciting prospects for elephants, a species highly susceptible to a virus that can induce fatal internal bleeding. Cryopreservation could enable zoos to bank the blood of elephant calves, allowing for autologous transfusions if they ever need their own blood returned to them. “They could donate their own blood to themselves,” Dr. Parkinson enthusiastically explains.
However, initial tests involving polar bear and emu blood proved less promising, Dr. Parkinson acknowledged. Nevertheless, she stressed that these were small samples, and further adjustments to the thawing protocol might be necessary to achieve better viability.
While this research remains in its nascent stages, Dr. Parkinson harbors a profound hope: that one day, zoos facing critically ill lions, lemurs, or leopards will be able to dedicate all their focus and energy to patient care, without the added burden of desperately seeking a rare pint of exotic animal blood. “You can just focus on the ill animal,” she affirmed, “and then maybe we can have a central blood bank that worries about all the other stuff for you.”