Blood transfusions are used daily to save human lives, but they are just as important for animals. In fact, the first blood transfusions were performed using animals. As we start to provide more advanced healthcare to cats and dogs, animal blood transfusions are becoming increasingly common.
Blood types (or groups) are determined by specific antigens found on the surface of erythrocytes, more commonly known as red blood cells. Humans have four main blood types, but this isn't universal to all living being - dogs have eight major blood groups, cats have three, cattle have 11, sheep have seven, goats have five and horses have over 30 different groups.
Funnily enough, the first step to a blood transfusion was performed more than 300 years ago in 1657, not by a doctor, but by the architect Christopher Wren, famous for the design of Saint Paul's Cathedral in London. He performed an intravenous injection of alcohol into a dog's veins. The technique was refined by British physician Richard Lower who performed the first-ever successful animal blood transfusion in 1665 on a dog.
The first-ever animal to human transfusion of blood was performed closely after, in 1667 by Frenchman Jean-Baptiste Denis. He transferred blood from a sheep to a 15-year old boy and a woman in labour. Both survived the process but severe anaemia occurred, and thus the concept of transfusion fell out of favour.
For a long time, blood transfusions remained a technically difficult procedure - the only available apparatus were animal quills or silver tubes - and there was no way of preventing blood from clotting. Even when Karl Landsteiner defined the blood groups in 1900, and recipients and donors could be precisely matched, Transfusions were rarely attempted.
Gradually, animal research enabled transfusion to become the routine technique it is today. The technique was first perfect in dogs, rabbits and guinea-pigs, and Adolph Hustin eventually found in 1914 that adding sodium citrate to the blood prevented it from clotting and allowed it to be stored safely for several days. With the prolonged storage of blood made possible, blood banks could be established and blood transfusion was on the way to becoming a routine procedure.
Today, research has even come up with ideas that might get around the worldwide blood shortage and make blood donations as we know them obsolete. In 2011, a blood substitute derived from cow plasma was used to save the life of a woman with only 1 litre of blood left in her body but whose religion forbade conventional blood transfusion. This is one type of so-called artificial bloods that are designed to increase oxygen transport in the body after heavy blood loss.
Scientists are also looking at blood substitutes that come from sea creatures. Animal haemoglobins can cause allergic reactions and even damage the kidneys. But the larger haemoglobin from a common marine worm (Arenicola marina) has shown none of these effects in mice. This sea worm-derived blood should be transfused into humans by 2017 during a clinical trial.
Researchers have also been working towards creating a continuous supply of red blood cells from embryonic stem cells. This work was successful in mice and clinical trials in humans should be starting shortly.
Animal research has helped conceive, optimize and now upgrade from human blood transfusions so facilitating a critical, lifesaving procedure for both humans and animals. Fresh new blood can often make the difference between life and death. Nowadays, over 88 million blood donations are made each year for humans - enough to fill 32 Olympic-sized swimming pools - and it still isn't enough.