Anaemia in Cats

Anaemia describes a reduction in the amount of red blood cells in circulation and is a relatively common problem in cats.  Red blood cells are important for carrying oxygen from the lungs to all the organs of the body. If the number of red blood cells is reduced, organs can become short of oxygen.

What signs will anaemia cause?

The signs of anaemia will depend on the severity, the speed of onset of the anaemia, and the underlying cause. The speed of onset is particularly important because if the anaemia develops slowly, cats adapt to having a much lower number of red blood cells and may show no signs at all until the anaemia is extremely severe.  Most often, the signs will be vague, with the cat being more lethargic than normal, sleeping a lot more, and gradually becoming weaker and inappetant.  Anaemic cats may also exhibit something called ‘pica’, which is when they try to eat non-food substances, often stones or cat litter, or lick paving slabs or walls. If the anaemia develops rapidly, the cat may become extremely weak suddenly or collapse. Depending on the underlying cause, other signs may also be present, e.g. jaundice. If haemorrhage into the intestine is the cause of the anaemia, owners may notice the cat passing very dark or black faeces, representing digested blood.

What can cause anaemia?

There are a vast number of causes of anaemia, and the causes are usually spilt into 2 main groups, termed regenerative and non-regenerative anaemia. This refers to whether the bone marrow is responding to the anaemia and producing new red blood cells (regenerative).

Regenerative anaemia is caused by two main groups of disorders, either blood loss or excessive breakdown of red blood cells in the circulation.  Blood loss can be a result of trauma, a bleeding disorder, tumour, or ulceration in the gastrointestinal tract. It can also be caused by parasites such as fleas - a large flea infestation can cause significant blood loss from the large number of fleas drinking a cat's blood. 

Excessive breakdown of red blood cells in the circulation can occur for a number of reasons, including infectious diseases such as feline leukaemia infection, or Haemoplasma (a red blood cell parasite), an abnormal reaction to certain drugs, toxicity (e.g. paracetemol, ingestion of products containing onions or garlic), tumours, an abnormality of the immune system and rarely in some breeds due to a genetic abnormality.

If the anaemia is non-regenerative (ie the bone marrow is not responding to the anaemia and producing new red blood cells), this is reflective of either a disease within the bone marrow, or a severe disease elsewhere in the body that is stopping the bone marrow from functioning properly (e.g. kidney disease).

How is anaemia and the underlying cause diagnosed?

Anaemia is diagnosed by performing a blood test to assess the number of red blood cells and haemoglobin in the blood.  Your veterinarian may have a suspicion that your cat is anaemic if the gums are very pale, however there can be other reasons for pale gums and so it is important that this is confirmed with a blood test.  The blood test will also give more information about the anaemia.  Your veterinarian will look at blood cells on a microscope slide (or send this off to a laboratory) and by doing special stains and looking carefully at the size and shape of the cells, will be able to determine whether the anaemia is regenerative or non-regenerative, in addition to possibly giving other clues as to the underlying cause. Toxicities or problems with the immune system for example, can cause specific changes to the cells that can be seen by careful examination.

Further blood tests to look for jaundice, and problems with other organs such as the liver and kidneys will also need to be performed in addition to tests for infectious diseases like feline leukaemia virus infection.  If your veterinarian suspects that your cat has a bleeding disorder special blood tests may have to be performed to assess the ability of your cat’s blood to clot.  Radiography and ultrasound examinations may also be required to look for signs of internal bleeding or tumours, if blood loss is suspected.  If the anaemia is found to be non-regenerative, a bone marrow biopsy will be required to identify the underlying cause.  This is a specialised technique and so your cat may need to be referred to a specialist.

How is anaemia treated?

The treatment will very much be dependent on the underlying cause and the severity of the anaemia.  If the anaemia is very severe or has occurred very quickly, a blood transfusion could be required, until more specific treatment can be initiated.  Before your cat receives a blood transfusion, it will have to have a test to determine its blood type to ensure that matching blood is given. Dogs can accept blood from any other dog when first transfused, as there are no antibodies towards other blood groups, while cats do have naturally occurring antibodies to other blood groups and can have serious reactions to the wrong blood type. Therefore, it is important that blood typing needs to be performed for cats prior to the first transfusion.