Immune haemolytic anaemia in a cat
Tigs (a 5 year old male Burmese cat) was presented for being off colour, feverish, and very lethargic. The owners had noticed his urine was an abnormally dark yellow colour. He was in some discomfort when we examined his abdomen around the region of the liver. His temperature was elevated (41 degrees Celsius) and his gums and white of his eyes had a yellowish tinge to them (jaundice).
We collected some blood and placed some on a glass slide where we noticed the red blood cells (RBC's) were sticking together (clumping). When we spun some blood down in a small thin glass tube (a microhaematocrit tube), the serum was very yellow and he had lost approx 30% of his total circulating RBC's. By spinning the blood down in one of these tubes, we can measure what percentage of the blood is made up of RBC- the packed cell volume (PCV). Normally, the PCV is 35-45% but in Tigs's case, his PCV was 25%. In other words, only 25% of his blood was made up of RBC when it should have been 35-45%.
We suspected he had a condition where his immune system, for some reason or other, had decided to destroy his RBC. This often happens after the RBC have been changed in some way e.g. slightly different colour or some other slight change to their appearance.
An x-ray of his abdomen showed a very swollen liver which may have explained why he was uncomfortable with us palpating him.
The immune system detects these changes and starts to destroy the affected RBC.
The most active parts of the immune system involved in this process are the liver and spleen. The waste product of destroyed RBC, Bilirubin, is a yellowish pigment which the liver excretes in the bile into the intestines. When a large number of RBC are destroyed, some of the Bilirubin finds its way into the blood stream causing the yellowness of the skin and white of the eye. It also appears in the urine.
The immune system also generates antibodies to "fight" the abnormal RBC. These antibodies circulate in the blood and attach themselves to the surface of affected RBC. They make the affected RBC "sticky" hence the clumping we see on the slide. This is called Auto Immune Haemolytic Anaemia (AIHA)
We ran some blood test to rule out infections that are known to cause such problems: Feline AIDS, Feline Leukemia and Haemobartonella Felis (H. Felis) - a tiny parasite that lives inside RBC).
Although the H. Felis result was negative at the local laboratory, it did not rule it out. A more accurate test is done at Bristol University in the UK but time was against us. As a precaution we started treating for H. Felis anyway using Oxytetracyline antibiotics.
The owners mentioned they had given Tigs a supermarket brand of worming tablet the week before which could have been the cause of the condition if he was "allergic" to the ingredients in the tablet. Other known causes of damage to RBC are compost, onions, garlic, mothballs and just straight out allergic type reactions to a new medication.
We started Tigs on cortisone tablets with the Oxytetracyline, and within 24 hours he was back to his old ticks. His temperature was normal and he was not so sore in the abdomen.
Over the next few weeks, the amount of jaundice in blood tubes reduced to clear and his PCV rose to 41%. He is now on a very low dose of cortisone tablets and appears to be doing very well. We hope to have him off all medications in the next 2 weeks.