Dr Lily Parkinson wants to establish America’s first frozen blood bank for zoo and aquarium animals. Photo / Jamie Kelter Davis, The New York Times
Several years ago, in the thick of the Covid-19 pandemic, Dr Lily Parkinson, who was working as an emergency and critical care veterinarian at the University of Georgia, began getting calls about snow leopards.
By then, the coronavirus had jumped into a variety of zoo animals, but snow leopards seemed to be getting unusually ill.
Some were developing severe anaemia, a shortage of red blood cells that can leave the body critically short of oxygen.
Had the patients been human or even domesticated cats, treatment would have been routine: a transfusion of red blood cells from an established blood bank.
But there were no blood banks for snow leopards, and veterinarians knew little about blood types and compatibility in exotic animals.
So zoos scrambled to find suitable blood donors. Institutions with healthy snow leopards offered to sedate their animals, draw their blood and send it to Parkinson, who just happened to be in the middle of a research project on blood types in large, wild cat species.
The logistical challenges were enormous, and in many cases, insurmountable.
The zoo employees who were needed to collect the blood were out sick. Samples were lost in the mail.
“Other zoos that really wanted to donate and help were just not able to drop everything that they already had on their schedule,” Parkinson said.
Some of the leopards’ health deteriorated so fast that they had to be euthanised before transfusions could be arranged.
Today, Parkinson, now a clinical veterinarian at Brookfield Zoo Chicago, is trying to lay the groundwork for a resource that might have given some of these animals a chance: a blood bank for zoos and aquariums, stocked with prescreened blood from a menagerie of exotic animals.
To make this possible, she is drawing on techniques in human medicine that allow delicate red blood cells to be preserved, on ice, for years.
If she can do the same thing for polar bears, pangolins, dolphins and dik-diks, it could leave zoos far better prepared for future animal health emergencies.
“We could theoretically try to bank every animal that we have in zoos and have it frozen and ready,” she said.
Blood, whether human or animal, consists of several components, including red blood cells, which ferry oxygen around the body, and plasma, the liquid in which those cells are suspended.
Some zoos already collect and bank plasma, which is easy to freeze and is packed with nutrients, antibodies and other important proteins.
Zoos sometimes use plasma transfusions to treat newborn giraffes, which often fail to acquire critical antibodies from their mothers.
Animals suffering from an array of infectious or chronic diseases or experiencing massive blood loss may need transfusions of red blood cells, which have a tendency to burst when frozen and thawed.
In human medicine, red blood cells are frozen in some limited circumstances – to store very rare blood types, for instance, or to ensure a steady supply of blood in combat zones.
The freezing process, which can preserve the cells for a decade or more, is complex, expensive and labour-intensive.
So human blood banks, which tend to go through their supplies quickly, typically refrigerate red blood cells, giving them a shelf life of about six weeks. Unfortunately, Parkinson said, “that just doesn’t fit the timeline of what you need in a zoo”.
Zoos don’t do transfusions often, and red blood cells vary widely in 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,” Parkinson said.
A refrigerated blood bank would require regularly collecting blood from many different species, much of which would be discarded without being used.
Last year, Parkinson received a grant from the American Association of Zoo Veterinarians to investigate the feasibility of freezing red blood cells from a variety of exotic species.
“It’s a technology that’s in human medicine but really kind of forward-thinking in terms of veterinary medicine,” said Dr Taylor Yaw, the vice-president of science and animal health at the Henry Doorly Zoo and Aquarium in Omaha, Nebraska, which is 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?”
Now that she has funding, Parkinson is trying to “collect as much blood as I can,” she said, piggybacking on the regular health examinations given to the animals at Brookfield Zoo Chicago.
On a Friday morning last month, a clouded leopard named River was scheduled for a check-up.
The veterinary team sedated the 8-year-old cat and then gave her a head-to-tail work-up, including a dental exam, CT scan and an ultrasound. Then, they drew about a quarter of a cup of her blood and passed it on to Parkinson.
Parkinson spun the blood in a centrifuge to separate the red blood cells from the plasma and then slowly added a glycerol solution to protect the cells during freezing. She stashed the sample in a freezer that held a growing collection of red blood cells, including samples from gorillas, bottlenose dolphins, a polar bear, and a pangolin.
Simply gathering the samples had been a feat, requiring patience and creativity.
Parkinson had needed to cobble together tiny, 20ml blood bags – “I think they’re adorable”, she said – for the smaller donors, including koalas, pangolins, and dik-diks, a cat-size antelope native to Africa.
Parkinson is receiving samples from other institutions too: beluga whale blood from the Shedd Aquarium in Chicago, elephant blood from the Henry Doorly Zoo and Aquarium, and giraffe blood from the Cheyenne Mountain Zoo in Colorado Springs, Colorado.
The Cheyenne Mountain Zoo, which had previously helped establish a national plasma bank for giraffes, had trained some of its animals to cooperate with blood draws without needing to be sedated.
“We’ve got giraffes that will stay for upward of 20 minutes and allow us to draw plasma,” said Amy Schilz, a senior animal behaviourist at the zoo’s giraffe centre. In exchange for their efforts, the giraffes receive rye-crisp crackers, she added, “which is essentially like giving them a candy bar”.
The zoo had previously helped Parkinson obtain samples for a study of giraffe plasma, and Schilz was happy to help her expand her work to red blood cells. “I’m all in,” Schilz said. “Just tell me what you need, and we’re going to go get it.”
The real challenge will come after the cells have spent six months on ice. At that point, Parkinson will thaw each sample, carefully wash away the glycerol solution and, as she put it, “compare it to how happy it was before I froze it”.
She’ll assess how many cells survived intact, whether they look normal under a microscope and whether they are still metabolically active, among other things. She will also evaluate whether the cells can withstand automated washing by a machine or must be processed by hand, a far more labour-intensive process.
Early results suggest that red blood cells from giraffes and elephants do not “appear to mind being frozen”, Parkinson said.
That could open up some exciting possibilities for elephants, which are prone to a virus that can cause fatal internal bleeding.
Cryopreservation could allow zoos to store the blood of elephant calves and then transfuse their own blood back to them if needed. “They could donate their own blood to themselves,” Parkinson said.
Initial tests with polar bear and emu blood were not as promising, Parkinson said, adding that she has only tested small amounts of blood from those animals and may need to adjust the thawing protocol.
The research is still in its early stages.
Parkinson hopes that one day, zoos with critically ill lions, lemurs or leopards will be able to devote all of their energies to caring for their patients instead of having to track down a pint of 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.”
This article originally appeared in The New York Times.
Written by: Emily Anthes
Photographs by: Jamie Kelter Davis
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