Iron deficiency in dogs and cats

We have recently seen a number of cases of iron deficiency anaemia, both in cats and dogs.
In iron deficiency, red cells do not develop the normal complement of iron–containing haemoglobin and the cells that form in the bone marrow are small (microcytic, low MCV) and hypochromic (low MCH and MCHC). The process of red cell maturation becomes prolonged so young red cells no longer contain large amounts of RNA and therefore do not appear polychromatic. As a result the anaemia is non- regenerative, with inappropropriately low reticulocyte counts. There is often a marked increase in variation in red cell shape (poikilocytosis) and red cell fragments (schistocytes) are often seen, as above.
In cats, the red cells are often so small that platelets appear larger than red cells and this overlap in sizing can contribute to apparently very high platelet counts as some automated counters include some small red cells in the platelet count.
Iron deficiency anaemia reflects chronic external blood loss, either through the gut associated with bleeding tumours or ulcers or occasionally with severe flea burdens and parasitic blood loss.
Serum iron, iron panels (including serum iron, total iron binding capacity, transferrin and % saturation) and occasionally staining bone marrow for iron, can all be useful in investigating these cases in addition to a full blood count (which must include smear evaluation since not all cases have a low MCV and MCHC). Occult faecal blood testing, after a minimum of three days off all red meat, is useful to check for blood loss in cases where blood loss is not detectable grossly.
While most non-regenerative anaemias have a poorer outlook, iron deficiency responds excellently and quickly to treatment that is aimed at stopping the blood loss and providing oral iron supplementation. Our current crop of iron deficiency anaemia cases all appear to be doing well now that they are on treatment.
For more information on iron deficiency anaemia visit www.ctdslab.co.uk

About the Author

Nick graduated from Edinburgh Veterinary School in 1980 with an
Honours degree in Pathological Sciences and in 1982 as a Bachelor
of Veterinary Medicine and Surgery. In 2003 Nick became a diplomate
of the Royal college of Pathologists in veterinary clinical pathology.