Animal blood products key to human diagnostic testing
Odds are you or someone you know has been diagnosed by a doctor with an infection or a more serious disease. The doctor sent out for a test to determine what was afflicting you and the best course of treatment to heal you. This process occurs in 60 to 70 per cent of medical diagnoses. In the best case scenario, the test revealed what your ailment was, the doctor prescribed medicine, and the treatment was a success. You probably thanked the doctor and went merrily on your way. Whom you didn’t thank — and probably didn’t know to — were the animal blood donors that made the test possible.
Lifeblood of Medical Testing
Those animal donors are typically horses and sheep, and they give blood much as human donors do, often even receiving a nice treat for their troubles. There are only a couple dozen companies across the world dealing in animal blood products, but with the number of hospitals and pathology laboratories requiring agar plates for diagnostic testing, the market is lucrative and the mission critical.
Serum Australis is one such company, supplying horse and sheep blood products to university research and teaching labs. The horses Serum Australis uses are primarily retired harness racers who live on a farm the company runs in Manilla, NSW. There are 250 of them, and they are bled in rotations, with each horse donating 10 litres every three weeks. In all, Serum Australis collects about 350 litres of horse blood per week, fetching around $40 per litre.
“It took from 2002 until the end of 2010 before we actually had supply agreements with companies big enough to make us a proper business,” managing director Gavin Heywood told the ABC. By 2024, the global market for animal blood and plasma products is expected to be worth $2.75 billion, according to a Transparency Market Research analysis.
The horses and sheep on Serum Australis’ farm are handled with low stress techniques that keep the animals’ trust and cooperation whilst minimising pain. Their donations go toward such research as vaccine development. Sheep’s blood is used to test strep throat and urinary tract infections, among other ailments; horses’ can be used in detecting respiratory infections and venereal diseases, and horse serum played a big role in the diphtheria vaccine.
“It’s something that the average person will never think of, but it’s very, very important to the medical industry,” Jennifer “J.R.” Tonjum of Quad Five Ranch in Montana — one of a handful of US suppliers — told the Great Falls Tribune.
Why Not Use Humans?
When human blood is used in agar plates — Petri dishes filled with jelly made from algae that microbes can grow in — pathogens can fail to grow, rendering the plate far less accurate or even unusable. Human blood also can be dangerous for researchers to handle, especially in parts of the world where HIV/AIDS and hepatitis are common.
Pathologists use tens of millions of agar plates each year, and there simply aren’t enough human donors to provide samples, especially when human blood is going toward transfusions that animal products can’t be used for. Plus, with defibrination — a process in which coagulants are removed to keep the collection in a liquid state — animal blood can stay fresh for several weeks, enabling shipment across the globe. There are many more hurdles to sending human biological products past international borders than animal products.
“Think about a huge hospital and how many agar plates they’re going to have,” Tonjum said. “Then multiply it by all the doctor’s offices, all the hospitals, all the academic labs and all the universities in the world.”
It adds up to a lot of regulation, and a lot of revenue for the companies supplying samples. Under the Animal Research Act 1985, the Animal Research Review Panel and the NSW Department of Primary Industries monitor the welfare of the animals on Serum Australis’ farm. “Every time the horses come in, they have special checks and if everything is OK we can go ahead and bleed them,” production manager Kay Whistler told the ABC. If something is not right, the animals aren’t bled. The US Department of Agriculture similarly inspects Quad Farm once a year.
Animals that donate eat special monitored diets that are kept as chemical free as possible, something that cannot be guaranteed in human donors. All in all, it’s safer and more practical to use animal blood for diagnostic testing.
Use in the Developing World
Animal blood products are a staple in developed nations, and studies have shown it could work wonders in the developing world. In poorer countries where horses are an extravagance and long-haired sheep don’t fare well in the heat, diagnostics labs still use human blood in their agar plates. It’s often expired, which makes it difficult for pathologists to view and measure bacterial growth on the plates because of the age of the cells, not to mention the contamination risks.
Enter hair sheep, several breeds that grow coats much shorter than their wool-bearing counterparts and shed naturally, eliminating the need for shearing. Their blood, when treated with a citrate of sodium or potassium, is much more effective in providing accurate diagnoses in agar plates than that of humans. The citrate acts as an anticoagulant in place of more expensive and labour intensive defibrination processes.
“Hair sheep may already be available in some developing world countries, otherwise they could easily be imported given their adaptability to tropical environments. A 50-60 pound sheep may yield about 350 ml of blood every six weeks, which can be directly collected into standard veterinary blood bags that contain the proper amount of citrate for anticoagulation while preserving the sterility of the blood during collection,” a breakthrough 2009 Stanford School of Medicine study concluded.
One of the authors of that study, Dr Ellen Jo Baron, now sits on the board of directors of the Diagnostic Microbiology Development Program (DMDP). The program maintains a flock of sheep in Cambodia as part of its mission to halt infectious diseases in developing countries. There is still a great deal of need in Asia-Pacific, and a great deal of opportunity in a growing industry for ranchers in a country with plenty of sun and wide open spaces.
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