FIA is an infectious disease of cats caused by a group of bacteria called Haemoplasmas (although they used to be called Haemobartonella, they have recently been reclassified by experts as Mycoplasma). There are three main species, but only Mycoplasma haemofelis is likely to cause clinical disease. These bacteria live by sticking to the outer surface of red blood cells, damaging and destroying them, and causing anaemia.
How is it spread?
The bacteria are transmitted from blood to blood, most commonly during fighting; they can also be transmitted from saliva to blood (so in bite wounds). It is possible that fleas can transmit them from cat to cat, but we do not yet know how significant this route is.
Which cats are at risk?
Potentially any cat, but younger adult toms (who are more likely to fight) appear to be at the highest risk.
What is the effect on the cat?
The bacteria on the red blood cells may directly damage the cells; however, when the immune system attacks them, it can also destroy the red blood cells they’re stuck to. As a result, this can appear very similar to immune anaemia (immune-mediated haemolytic anaemia). The red blood cells carry oxygen around the body, so a lack of functional cells (anaemia) results in poor oxygenation of the tissues.
What are the symptoms?
Although there may be a fever, the main symptoms are those of anaemia:
- Pale gums
- Tiredness, weakness and lethargy
- Sometimes, a reduced appetite
- Weight loss
- Jaundice (due to breakdown of red blood cells)
- Increased breathing and heart rate
- In severe cases, collapse, difficulty breathing and death
How is the disease diagnosed?
The gold standard is to see the bacteria on the red blood cells when examining a blood sample using a microscope. However, even in clinically severe disease, most red blood cells will be unaffected, so this is not always reliable.
Modern laboratory techniques such as genetic testing for Mycoplasma DNA (a PCR test) is the best test currently available.
It is important to remember that the transmission of FIA is by the same routes as Feline Immunodeficiency Virus (FIV, or Feline AIDS) and Feline Leukaemia Virus (FeLV), so it is always worth testing infected cats for these viruses as well. Infection with one of these viruses as well as FIA usually results in much more severe anaemia.
Is there any treatment?
Yes, the use of antibiotics such as doxycycline will suppress the bacteria and allow the cat to recover. Other antibiotics such as enrofloxacin may also be used; however, in both cases long courses (two to four) at high doses are needed, and there is a risk of causing damage to the retinas and blindness with enrofloxacin, so doxycycline is usually preferred.
Sometimes, drugs like steroids may be used to “tone down” the cat’s immune system and reduce the destruction of healthy red blood cells, but this can make the infection worse, so is usually reserved for cases where antibiotics alone are insufficient.
In very severe anaemia, where the cat is unable to circulate enough oxygen, blood transfusions may also be needed.
How effective is treatment?
Most infected cats will make a good recovery if treatment is started early enough. Unfortunately, however, antibiotic treatment usually cannot completely clear the bacteria from the cat’s system, and many cats will become chronic carriers for many months or even years. These carriers are usually apparently healthy and show no symptoms, but occasional relapses are possible, especially when the cat is stressed or ill with some other condition.
How can the disease be prevented?
There is no vaccine for FIA; the best prevention is to minimise flea transmission (with good flea control) and fighting (by neutering cats, or restricting their access to other outdoor cats).
If you are concerned your cat’s gums are pale, or they have any other suspicious symptoms, make an appointment to get them checked out by one of our vets as soon as possible.
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