Blood transfusions are of importance not only in human medicine. Also animals do need blood donations. The University of Veterinary Medicine, Vienna operates a blood bank for dogs for more than a decade. But also cats can donate blood for acute emergencies. Horses need blood donations especially during operations that involve high blood loss. Sheep, goats and other ruminants require transfusions when plagued by serious infestations of parasites. Three vets from different areas of expertise explain how blood transfusions work with different animal species and how they can save lives.
Blood can hardly be created through artificial means, but it can be transferred within a species. Reasons for a blood transfusion among dogs and cats are usually serious accidents, large operations, certain types of cancer, cases of intoxication with rat poison, serious infectious diseases such as the tick-borne babesiosis, and blood illnesses including haemolytic or inherited bleeding disorders such as haemophilia.
At the University of Veterinary Medicine, Vienna dog owners can bring their animals to donate blood regularly or as needed. Blood donations two to four times a year per dog is the maximum. About 15 minutes are required for a donation. Dogs must have a minimum weight of 25 kilograms and usually donate about 450 millilitres of blood. For cats, depending on their size, the amount taken is about 50 millilitres. Cats are typically sedated for the procedure. For most dogs, on the other hand, donating blood does not involve any serious stress. Should a donation cause too much anxiety or stress, the animal will be excluded as a donor.
As with people, animals also have different blood types. Animal blood, as well as human blood, is divided into various groups based on different surface proteins found on the red blood cells. More than twelve different blood type systems have been described for dogs, although in practice dogs are only tested for DEA 1.1 positive or DEA 1.1 negative. Cats exhibit three different types of blood, horses eight and bovines eleven. The transfusion of an unsuitable blood type can have fatal consequences for animals, especially when a cat with blood type B receives type A blood. For horses and ruminants, the first time transfusion of ‘wrong’ donor blood is generally safe. With each additional transfusion, however, blood types become crucial, as the animals have produced antibodies against the foreign blood that can cause serious immune reactions.
Dogs and cats can be registered as blood donors at the Clinical Unit of Internal Medicine Small Animals of the Vetmeduni Vienna. The animals receive a donor card and undergo a thorough examination before each donation. This mandatory health check includes a complete blood count, a test for blood parasites, and a check-up for viral infections.
“Donating blood does not harm the animals. The donated amount can be quickly regenerated by the animal’s organism,” says specialist for small animal internal medicine and blood bank coordinator Nicole Luckschander-Zeller. “We pay special attention to making sure that donor animals feel good during donation. That’s why, after every donation, we give the animals a little snack.”
Dog and cat blood is not only used as a whole. Individual blood components, such as plasma or erythrocyte concentrates, are stored and used when needed.
There are various reasons for blood donations in equine medicine. These include clotting disorders of the blood, anaemia, poisonings or serious infectious diseases as well as perioperative blood loss. For the latter, blood is stored and kept ready for use during surgery in areas with strong blood supply, such as the nose and jaw. A blood transfusion helps to sustain adequate circulation of the animal during the operation and speeds recovery.
“The owners of diseased horses occasionally bring the suitable donor animal with them,” says René van den Hoven, director of the Clinical Unit for Equine Internal Medicine at the Vetmeduni Vienna. The hospital also maintains a number of its own donor horses. The number of donations and the volume of the blood collected are registered in the horse’s file, making it possible to plan future dates for donations without compromising the animal’s health.
A maximum of five to seven litres of blood can be collected from a horse per donation. The blood must then be transfused into a patient within just a few hours. Storing whole equine blood is not a suitable option. As only plasma is desired for some treatments, the plasma is separated from the whole blood. Plasma is used for specific applications, for example to improve the healing of complicated wounds or during eye operations. Patients with massive protein loss can also be successfully treated with plasma. Protein loss may occur as a consequence of serious burn trauma, severe diarrhoea, tumours or chronic inflammatory intestinal disease, pleurisy or peritonitis.
Sheep, goats, lamas and alpacas are especially at risk of being infested by blood-sucking parasites out on the pasture. Ingested through the mouth, the worms come to inhabit the intestinal tract. A high level of parasitic infestation leads to serious cases of anaemia that may be fatal for the animals. “These acute patients require a rapid blood transfusion. Ruminants also receive blood for wounds with heavy blood loss, though this luckily is not often the case,” explains the specialist for ruminant medicine, Lorenz Khol.