In life-or-death situations, vets sometimes must make decisions as to the best route forward for your pet. In the case of blood loss or severe anaemia, this can mean that your pet requires more red blood cells, urgently. Most vet practices are not like large human hospitals. Therefore they don’t have a ready stash of blood for transfusion tucked away. While an amazing service called the Pet Blood Bank is there to supply vet practices with canine blood products, they are not yet in a position to offer feline blood.

If a suitable feline donor cannot be found for your sick cat, then a dog could be used in an emergency. So yes, it is true – dogs can give their blood to cats in this sort of extreme situation.

We’re going to explore how that works as well as some of the limiting factors of cats receiving blood transfusions from other species.

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Why might a cat require a blood transfusion?

A cat that is suffering from severe anaemia (a decrease in the amount of normal circulating red blood cells) may require a blood transfusion. This is made much more likely if the anaemia has occurred very rapidly, rather than over a longer period where the cat has been able to gradually adapt and compensate. 

An animal with severe anaemia will often be in shock and may have the following symptoms –

  • Pale pink or white mucous membranes
  • A yellow tinge to their mucous membranes (jaundice or icterus can occur due to the breakdown of red blood cells)
  • Increased heart rate and breathing rate
  • Lethargy
  • Changes in appetite
  • Collapse

What conditions could cause anaemia in cats?

Many different conditions could cause a reduction in red blood cells in your cat. These can be regenerative, where the bone marrow responds to produce new red blood cells, or non-regenerative, where the bone marrow is unable to create new cells. However, overlap can occur within diseases which can confuse. Also in some cases, like trauma, the bone marrow hasn’t had a chance to start producing new red blood cells yet. 

The following are some of the more common causes of anaemia in cats, however, it is not exhaustive –

Anaemia from blood loss – 

  • Trauma 
  • A bleed from an internal tumour or ulcer
  • Bleeding due to issues with blood clotting (this could be due to something like ingestion of rodent bait)

Haemolytic anaemia (the red blood cells become broken down) –

  • Feline leukaemia virus (FeLV) infection
  • Infection with infectious organisms like Mycoplasma haemofelis infection (feline infectious anaemia, formerly known as Haemobartonella felis infection which can be spread through a bite from an infected flea)
  • Immune-mediated haemolytic anaemia (IMHA – the cat’s own immune system is attacking the red blood cells)
  • Eating certain toxins such as garlic or onions, or paracetamol (acetaminophen)
  • Neonatal isoerythrolysis – an issue seen in very young kittens. This occurs when there is an incompatibility between the blood type of the kitten and its mother

Non-regenerative anaemia (the bone marrow struggles to make new blood cells) – 

What tests will my vet need to do to diagnose the problem?

Unless there is an obvious bleed/trauma, your vet may have to perform some tests to make a diagnosis. 

This usually consists of haematology blood tests to check their red and white blood cell levels. A machine can perform blood cell counts of these or your vet may do a test called a manual packed cell volume (PCV). Here a small amount of blood is spun down in a thin glass tube inside a centrifuge. The red blood cell sediment at the bottom can be measured. 

Your vet will probably want to examine your cat’s blood on a microscope too, which helps them to look directly at the red blood cells. In some conditions the red blood cells may change in appearance, so looking at them up close like this can help. It may also determine whether the anaemia is regenerative or non-regenerative, as your vet can see if there are any young/immature blood cells being produced by the body or not.

Your vet will want to run a biochemistry panel to check organ function as well as a screen for FIV and FeLV viruses.

Many of these tests can be run in the veterinary clinic, but sometimes your vet will need to send samples away to the lab for more specialised screens. 

In some cases, your vet may also need to perform diagnostic imaging like x-rays or ultrasound, particularly if they are suspicious of an underlying tumour or an internal haemorrhage issue. In some cases, bone marrow samples could be required too.

How does blood transfusion work in cats?

Blood transfusion is typically less common in cats than it is in dogs. And the short shelf-life of stored blood means that most veterinary practices are unable to keep it in stock. This can mean that in an emergency freshly collected blood may need to be transfused instead. 

In cats, this relies on having a donor cat available that matches the recipient’s blood type. Type A cats are much more common than type B cats, so this can be problematic for some individuals. It is not possible to use type A blood in a type B cat, or vice versa as this is usually fatal. 

It also relies on finding a donor cat that is negative for any infectious diseases and is also fit and healthy enough to donate, under emergency time pressure. These cats must weigh more than 4kg, be fully vaccinated and treated for parasites, and must never have travelled abroad. Even then many donor cats need to be sedated or anaesthetised to be compliant enough with donation, unless they have a docile temperament.

This is where xenotransfusion may come in

Xenotransfusion is where the blood is taken from one animal and transfused to another. While not commonly practised, it has been shown in some settings that anaemic cats receiving dog blood are well-tolerated for single emergency-type episodes of transfusion (any additional transfusions could be fatal however, as the cat will develop strong antibodies against the dog blood). Dogs tend to be more compliant with the donation process; and don’t carry the risk of passing on feline infectious diseases.

Dog blood does not last for long in cats (approximately 4-7 days before being cleared), but it has the advantage of often being much more readily available than feline blood, especially for less common type B cats. However this may give your vet more time to find a feline donor for a second transfusion, or it may be that your cat doesn’t require another transfusion at all after this. It has been shown that a second transfusion has only been required in a third of cases.

However, other studies have shown potential issues with canine to feline transfusion, with transfusion reactions being a possibility. There is some conflicting evidence as to how severe these reactions might be. But it is generally accepted that xenotransfusion should not be carried out routinely. It is best reserved for only true emergencies that cannot wait for a suitable feline donor to be found.

Summary 

Dogs can be used as blood donors for cats, but only as a single one-time emergency transfusion. This can be life-saving for your cat, but as with any procedure, there is always the risk of complications. It is accepted that it is best if your cat can receive feline blood (of the correct A or B type). But this is not always readily available in an emergency.
If you are interested in whether your cat could be a feline blood donor then why not take another look at the Pet Blood Bank? They are looking for owners to register their cats with them, in case they can extend the services they offer in the future. You could also contact your local vet. Some practices keep a list of emergency donors that they can call on for help in the future. Your pet could help to save the life of another.

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