During the intense early days of the Covid-19 pandemic, Dr. Lily Parkinson, then an emergency and critical care veterinarian at the University of Georgia, found herself facing an unusual and heartbreaking crisis: calls regarding snow leopards. While the coronavirus had affected many zoo animals, these majestic cats were becoming exceptionally ill. Many developed severe anemia, a critical shortage of red blood cells that starves the body of vital oxygen.
For human patients, or even our beloved household pets, the treatment would have been a straightforward, routine transfusion sourced from an established blood bank. But for snow leopards, such a resource simply didn’t exist. Veterinarians at the time also had limited knowledge about blood types and compatibility in exotic animals.
Zoos quickly mobilized, with institutions fortunate enough to have healthy snow leopards offering to sedate their animals, draw blood, and send it to Dr. Parkinson. This was serendipitous, as she happened to be researching blood types in large, wild cat species. However, the logistical hurdles were immense, often proving impossible to overcome. Zoo staff, vital for blood collection, were often ill themselves. Precious samples were lost in transit, and other zoos, despite their eagerness to help, simply couldn’t drop their demanding schedules to facilitate donations.
Tragically, some leopards deteriorated so rapidly that they had to be euthanized before a suitable transfusion could even be arranged.
Today, Dr. Parkinson, now a clinical veterinarian at Brookfield Zoo Chicago, is on a mission to prevent such tragedies from happening again. She is diligently working to create a groundbreaking resource: a comprehensive blood bank for zoos and aquariums, meticulously stocked with pre-screened blood from a diverse array of exotic animals.
Her ambitious project draws inspiration from advanced human medicine techniques that allow delicate red blood cells to be preserved, frozen solid, for many years. If she can successfully adapt this method for the unique blood of polar bears, pangolins, dolphins, and even tiny dik-diks, it would revolutionize how zoos prepare for and respond to urgent animal health emergencies. “We could theoretically try to bank every animal that we have in zoos and have it frozen and ready,” she explains.
The Challenge of a Short Shelf Life
Blood, whether from humans or animals, is composed of various crucial elements. Red blood cells are responsible for transporting oxygen throughout the body, while plasma, the liquid component, carries vital nutrients, antibodies, and proteins. Many zoos already collect and bank plasma because it freezes easily without damage. Plasma transfusions are often used for situations like treating newborn giraffes that struggle to acquire essential antibodies from their mothers.
However, animals suffering from severe infections, chronic illnesses, or massive blood loss frequently require transfusions of red blood cells. The significant challenge here is that red blood cells are notoriously fragile and tend to burst when frozen and subsequently thawed.
In human medicine, red blood cells are frozen only in very specific, limited scenarios—for instance, to store extremely rare blood types or to ensure a stable supply in combat zones. The freezing process, while extending shelf life to a decade or more, is complex, costly, and labor-intensive. Most human blood banks rely on refrigeration, which gives red blood cells a shelf life of approximately six weeks. Unfortunately, as Dr. Parkinson points out, “that just doesn’t fit the timeline of what you need in a zoo.”
Zoos don’t perform transfusions frequently, and critically, 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 notes. Maintaining a refrigerated blood bank for dozens of distinct species would mean constant collection, with a significant amount of valuable blood inevitably expiring and being discarded.
Last year, Dr. Parkinson received a vital grant from the American Association of Zoo Veterinarians to explore the feasibility of successfully freezing red blood cells from a wide range of exotic species.
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 project, describes the work as “forward-thinking in terms of veterinary medicine.” He poses the central question: “Can we freeze these red blood cells, cryopreserve them, and then basically wake them up at a future date?”
Into the Deep Freeze: Building the Collection
With crucial funding now secured, Dr. Parkinson’s primary goal is to “collect as much blood as I can.” She strategically coordinates these collections with the routine wellness exams already scheduled for animals at Brookfield Zoo Chicago. On a recent Friday morning, River, an 8-year-old clouded leopard, was in for her annual checkup. The dedicated veterinary team gently sedated River, 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 spun the blood in a centrifuge to separate the red blood cells from the plasma. She then slowly introduced a glycerol solution, a crucial step designed to protect the delicate cells during the freezing process. The sample was then added to a specialized freezer, where it joined a growing and increasingly diverse collection of red blood cells from animals including gorillas, bottlenose dolphins, orangutans, a polar bear, an emu, and a pangolin.
Even the act of gathering these samples is a testament to the team’s patience and ingenuity. Dr. Parkinson had to specially acquire tiny, 20-ml blood bags – which she affectionately calls “adorable” – for smaller donors like koalas, pangolins, and dik-diks, a cat-sized antelope native to Africa.
The collaborative spirit of the zoo community is also evident, as Dr. Parkinson receives samples from other institutions. These include 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 facility that previously helped establish a national plasma bank for giraffes, has even trained some of its giraffes to willingly cooperate with blood draws without needing sedation. “We’ve got giraffes that will stay for upward of 20 minutes and allow us to draw plasma,” says Amy Schilz, a senior animal behaviorist at the zoo’s giraffe center. She adds that in exchange for their cooperation, the giraffes are rewarded with rye-crisp crackers, which are “essentially like giving them a candy bar.”
Having previously assisted Dr. Parkinson with a study on giraffe plasma, Ms. Schilz expressed her full support for expanding the work to include 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: Testing Viability
The true test of Dr. Parkinson’s pioneering work will come after these precious cells have spent a minimum of six months in their icy slumber. At that critical juncture, she will carefully thaw each sample, meticulously wash away the glycerol solution, and, as she describes it, “compare it to how happy it was before I froze it.”
Her evaluation will include a comprehensive assessment of how many cells survived the freezing and thawing process intact, whether they appear normal under a microscope, and if they retain their vital metabolic activity, among other key indicators. She will also determine if the cells can withstand automated washing by specialized machines or if they require a more labor-intensive, manual processing method.
Encouragingly, initial results suggest that red blood cells from giraffes and elephants do not “appear to mind being frozen,” Dr. Parkinson shared.
This is particularly exciting for elephants, which are susceptible to a virus that can cause fatal internal bleeding. Cryopreservation could offer a revolutionary solution, allowing zoos to store the blood of elephant calves and then transfuse their own blood back to them if they become ill. “They could donate their own blood to themselves,” Dr. Parkinson explained.
However, initial tests with polar bear and emu blood have been less promising so far, Dr. Parkinson acknowledged. She remains optimistic, noting that only small amounts of blood have been tested from these species, and adjustments to the thawing protocol may yield better results.
While the research is still in its nascent stages, Dr. Parkinson holds a powerful hope for the future. She envisions a day when zoos faced with critically ill lions, lemurs, or leopards can fully dedicate their resources to patient care, unburdened by the frantic search for exotic animal blood. “You can just focus on the ill animal,” she said, “and then maybe we can have a central blood bank that worries about all the other stuff for you.”