Answer: The term ‘leukaemia’ is used (in any species, e.g. cat, dog or man) when some of the white blood cell circulating in the blood-stream show evidence of cancer. Theses cells show characteristic cancerous changes which can be recognized under the microscope.
In man and in the dog the cause of leukaemia is not yet established but in the cat it is known to be due to a virus, which has therefore been named feline leukaemia virus, or FeL V for short.
Infect the name of the disease is misleading since most cats infected with this virus do not develop leukaemia, and much more common problem is that the virus causes cancerous growths (malignant tumors) called lymph sarcomas to develop in one or more of the lymphoid tissues of the body. There are the lymph nodes, the thymus (an organ at the front of the chest), the spleen (an organ in the abdomen) or in the wall of the intestines. The signs shown by affected cats very according to the site of the growth; for instance, growth in the thymus (which are most common in young cats; especially Siamese) produce difficulty in breathing; in the intestine diarrhea; in the lymph nodes of the throat-difficulty in swallowing. They may also grow in other organs, such as the kidneys, nose and nervous tissue.
Furthermore, because cells from the lymphoid tissue are responsible for producing the various antibodies which give immunity against different diseases, the damage to lymphoid tissue produced by FeL V can result in the cat’s especially in young cat’s inability to develop or maintain adequate immunity against a variety of disease-producing organisms. This means that affected cat are more likely to develop such diseases as gingivitis (inflammation of the gum), feline infectious anaemia (FIA), feline infectious peritonitis (FIP) and respiratory infections.
In some cats, including half of those with lymph sarcomas, the virus causes anaemia (a lack of red blood cells) in addition to the other problems.
This is because the virus either destroyed a large number of the circulating red blood cells, or damages the red bone marrow which produces new red blood cells.
The virus can also damage developing fetuses inside the mother causing them to die during pregnancy, either early (not detectable and usually attributed to infertility), or late (abortion), or soon after birth (‘fading kittens’)
If one or more of these condition occurs in a group of cats kept together (e.g. in a single household), the possibility of infection with FeL V should be considered.
