Anaemia is actually a symptom, not a specific disease! Basically, it means that an animal’s (or a human’s!) blood can’t carry enough oxygen. This may be because there aren’t enough red blood cells (the most common reason), or because the red blood cells are in some way defective (for example, in iron deficiency, where they haven’t got enough haemoglobin to do their job efficiently).
What are red blood cells anyway?
In the blood of any mammal (dog, cat, horse, human, giraffe, whale… whatever!), there are two main types of cells. White blood cells, which are colourless (hence the name!) and fight infection, and red blood cells, which contain a chemical called haemoglobin. This chemical contains iron and is red, so the cells appear red (this is also why blood is red!).
Red blood cells are smaller than most other cells, and are described as being “biconcave” – they look a bit like doughnuts but with a membrane across the middle bit. They’re very flexible and can bend to fit through all the tiny blood vessels supplying the tissues. Their job is to carry oxygen from the lungs to all the other tissues – without oxygen, the body’s cells would die (which is what happens in gangrene).
Unlike almost any other cell, red blood cells (aka erythrocytes or RBCs) do not contain a nucleus (the “control centre” of the cell). This means they can’t make more of themselves, they have to be made by the bone marrow; and it means they have a finite lifespan (about 70 days in the cat, and 120 in the dog)
So what sorts of anaemia are there?
Loads! Fortunately, there are several ways we can divide them up…
Regenerative anaemias are conditions where although the patient is anaemic, the bone marrow is working hard to try and replace the red blood cells. This can be detected in the practice lab because it’s in such a hurry, it kicks out the immature red blood cells to start working before they’ve finished developing (a bit like a Victorian family sending out the children to work when they really need the money!).
The worse the anaemia, the less developed or “younger” the cells are – so in a mild case, they may just be a bit bigger than usual and not so well shaped, but in a severe case they may still have part of their nucleus remaining (like our family – if money’s a bit tight you just send the teenagers out to work, but if you’re starving, you send the younger kids as well).
Examples of regenerative anaemias would include blood loss anaemia and haemolytic anaemia.
Non-regenerative anaemias, however, are those where the bone marrow is no longer making new red blood cells (or at least not enough of them). Eventually, as the old red blood cells in the blood die off, anaemia will develop. This can be due to damage to the bone marrow (such as some cancers, radiation poisoning or certain toxins); insufficient “ingredients” to make new cells (for example, iron and some vitamin deficiencies); or a malfunction in the system that tells the bone marrow to make red blood cells (which happens in kidney failure).
Blood-Loss anaemia – where simple loss of blood has caused a loss of red blood cells.
Haemolytic anaemia – where the red blood cells are being destroyed somehow. This may be due to certain infections (e.g. Feline Infectious Anaemia in cats, or Babesia in dogs), or autoimmune disease (where the immune system starts attacking healthy red blood cells by mistake).
What are the symptoms of anaemia?
To some extent, of course, it depends how severe it is, but the symptoms may include:
- Pale or white gums
- Poor exercise tolerance
- Panting or difficulty breathing
- Rapid heart rate
What can be done about it?
The most important thing is to find out the underlying cause! Once we know why the animal is anaemic, we can treat the cause and hopefully fix the patient. Sometimes, the anaemia is so severe as to be life threatening; in these cases, we may need to perform a blood transfusion to “top up” the animal’s red blood cells until we can sort the problem out.