Wednesday, January 15, 2014

Vector Borne Diseases Part 5: Feline Infectious Anemia

Sticking with cats again today...

Feline infectious anemia is caused by the bacteria Mycoplasma haemofelis.  Mycobacteria are parasitic bacteria that lack a cell wall and are difficult to identify and grow in a culture.  Mycoplasma haemofelis was previously known as Hemobartonella felis.

Mycoplasma haemofelis is spread by the bite of an infected flea, although ticks, mosquitoes and lice have also been implicated.  Once in the new host the Mycoplasma attach to the red blood cells.  Eventually the cat's immune system recognizes the intruder and destroys it-but the red blood cells are destroyed along with it.  This leads to an anemia (low red blood cell count) and the symptoms that go along with it such as pale gums, weakness, lethargy, jaundice, and anorexia.  Some cats will have a fever.  Labwork will indicate a regenerative (the bone marrow is in overdrive trying to replace lost blood) anemia.  It can take one month from time infection until the cat becomes ill.

Diagnosis is often made based on clinical signs and finding the organism on a blood smear. However the organism is cyclic and can be missed by only looking at one blood sample.  A specialized test known as PCR can be sent out to a lab to confirm the diagnosis. However, this is a very treatable disease and often responds well to a course of Doxycycline (three to four weeks) or Enrofloxacin.  Prognosis is good if caught in the early stages of illness.  In addition to antibiotics other treatments may include prednisone (a steroid) to suppress the immune system and stop the destruction of red blood cells.  Supportive care such as appetite stimulants, special nutrient rich diets, force feeding or blood transfusions are also needed in some cases.

Prevention is aimed at flea control.  Transmission is only via vectors and cannot be spread directly between cats.  The exception may be mother to kittens but mode of transmisstion is unclear. Infected cats, once treated, remain carriers and recurrence is possible in times of stress.

There is a similar organism in dogs but it only appears to cause disease in dogs whose spleens have been removed.  This renders the dog unable to adequately remove diseased red blood cells from the circulation.

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