There are many reasons we see poorly pets here at Aurora. Some of the most serious illnesses we encounter are caused when there is a glitch during the ordinary everyday immunological functions of the body. Our bodies and those of our pets are extremely effective at dealing with attacks from viruses, bacteria and fungi, usually stimulating the immune system into action to deal with whichever pathogens we have encountered. The immune system is an extremely complex and clever network of cells, tissues and processes ranging from white blood cells - the frontline defenders - through to major organs such as the liver and spleen. There are a whole host of signalling systems that regulate the immune system and guide the body in its efforts to protect itself. However, sometimes these important immune processes can go wrong and actually contribute to an illness. These types of conditions are often referred to as ‘immune mediated diseases’. As the immune system is spread throughout all the different tissue types that make up the body, these diseases can affect many different organ systems. One particularly serious condition occurs when the immune system turns on the biological substance that feeds the body - blood.
Immune mediated haemolytic anaemia (IMHA) occurs when the body’s immune system starts to see normal red blood cells as ‘foreign’ material. Red blood cells are responsible for carrying oxygen around the body and are vital for the function of the majority of body tissues. When red blood cells are targeted and attacked by the immune system this can result in breakdown of these cells - a process called haemolysis- therefore the red blood cells can no longer carry out their vital function. In all species, IMHA can potentially be caused by the body ‘over-reacting’ to an infectious or inflammatory stimulus e.g. some cancers or conditions such as pancreatitis. However, in many cases there is no obvious reason why the immune system has started to attack these endogenous cells. Regardless of the underlying pathology which triggers the autoimmune process, the immune mediated destruction of the body’s red blood cells is always very dangerous and detrimental to the health of the animal.
Depending on the underlying cause and how severely or quickly the red blood cells are destroyed, we can see a wide range of clinical symptoms from pale mucous membranes, unsteadiness and loss of appetite through to complete collapse. Sadly on occasion patients can suddenly pass away due to the physiological stress of this condition.
One of the common clinical features of IMHA occurs because red blood cells carry a substance called bilirubin which is released when red blood cells are broken down. This pigment causes a yellow staining of the blood and the soft tissues of the body as it builds up. This is termed jaundice or icterus (and can also been seen in some types of liver disease). Along with the reduced oxygen carrying capabilities, jaundice will contribute to making these patients feel very unwell. Jaundice is not usually a feature of this type of condition in our feline patients.
A diagnosis of IMHA is usually achieved through blood testing. Sometimes we can detect very obvious changes on these tests which indicate that the patient’s blood is abnormal. However, sometimes reaching a diagnosis can be more complex and may include further blood work, x-rays, abdominal scans and occasionally specialist testing for infectious diseases (especially in cats).
Routine blood tests will usually show that an affected patient has an anaemia (a reduction in red blood cell count). We can also perform a simple test called a slide agglutination test which will show if the red blood cells are sticking together which is usually indicative of IMHA.
Whether we are suspicious of a patient having IMHA, or have confirmed our diagnosis through our tests, we then need to consider starting medical treatment as quickly as possible. Treatment is usually based on subduing the overactive immune system with medications called immuno-suppressants. This often involves the administration of high doses of a corticosteroid drug called prednisolone, however some patients may require the use of multiple different types of immuno-suppressant medications. If these treatments can stop the immune system’s attack, then the body will start to replace the lost red blood cells and our patient will start to improve.
As our patients start to get better we have to closely monitor them with regular blood tests. If things are going well then for some cases we would manage to gradually reduce the immunosuppressive treatments to a very low maintenance dose that prevents recurrence and some patients will eventually come off treatment altogether.
Depending on the underlying reason the patient has developed IMHA in the first instance, there may be major differences in how we approach their treatment. For example, if we think there is an underlying cancer or the disease is too severe it may not be fair on our pets to even consider treatment. In some severe cases animals may require blood transfusions and prolonged periods of hospitalisation which usually means transferring the patient to a specialist hospital. Sadly despite everyone’s best efforts, around 50% of animals with IMHA will succumb to the disease in some way.
Now back to Daisy.
Daisy had been a little off colour and bit unsteady on her feet one afternoon and later that day she collapsed. By the time she got to the practice she was back up on her feet again but the decision was made to run some blood tests which indicated that Daisy was suffering from anaemia.
Daisy then helped us out in a way as she had a positive slide agglutination test which immediately confirmed for us that she had some form of IMHA.
Daisy initially improved with corticosteroid based immunosuppressive medication but a few days into her therapy she took a turn for the worse as her body continued to destroy her red blood cells despite being on treatment. At this point her mucous membranes were slightly yellow (jaundiced) which will have been contributing to her feeling very unwell. On this occasion Daisy had further investigations, including x-rays and ultrasound to rule out other underlying causes of her disease, which were all negative. Her immunosuppressive treatment was increased further by upping her steroid dosage and adding in another immune-suppressant drug called ciclosporin.
Thankfully on her new medication Daisy felt much better and her red blood cell count made a steady improvement. Daisy was on treatment for about 3 months and during this period her blood levels were regularly monitored. Daisy made a great recovery and the good news is she has now been weaned off all her medications. We are all so pleased to have her back to normal. Now when she comes into the practice Daisy loves to play with the dog toys from our display –we think she has earned a treat!!!