Feline Infectious Anaemia
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Desciption
An infectious disease of the cat caused by Mycoplasma haemofelis which until recently was known as Haemobartonella felis. The organism is found on the surface of erythrocytes and is considered an opportunistic infection that causes illness following predisposing factors. It is possible to be transmitted via bite wounds, biting arthropods, via blood transfusions and from a queen to her kittens. The organism causes a cyclic parasitaemia in affected cats and infected animals despite mounting an immune response will become carriers of the organism.
Signalment
Almost half of the cats infected have concurrent Feline Leukaemia Virus (FeLV). The disease is common in roaming Tom cats 1-3 years old.
Diagnosis
The organism can be intermittently seen microscopically on the surface of red blood cells on Giemsa-stained blood smears. The organism stains blue and look like rings or rods.
Erythrophagocytosis may be evident and parasitised erythrocytes will become spherical.
The organism must be differentiated from Howell-Jolly bodies and other parasites. Due to the cyclic parasitaemia the organism causes, negative blood smears will not rule out the disease.
Additionally Immunofluorescence of blood smears can demonstrate the organism. Haematology will show a decreased packed cell volume and a regenerative anaemia.
Clinical signs
The peracute disease is associated with severe anaemia and immunosuppression, and can be rapidly fatal.
Fever, anaemia, depression, weakness and jaundice occur in the acute form. In the chronic form animals present with anaemia, lethargy and weight loss. Cyclic fever may also occur during the transient period of parasitaemia. Recovery can occur with a regenerative bone marrow response however severe anaemia may occur in the presence of feline leukaemia virus (FeLV).
Treatment
Infected cats should be treated with doxycycline for 3 weeks twice daily. Enrofloxacin is also a good treatment choice especially in refractory cases when combined with doxycycline. A blood transfusion may als be required in cases of severe anaemia.
As blood sucking endoparasites such as Fleas are thought to spread disease the animal should also recieve flea treatment.
Prednislone is also advised to treat the immune mediated mechanisms and to prevent further erythrophagocytosis.
Prognosis
Varied depending on the severity of the anaemia at presentation. If not treated 1/3 of affected animals will die. Antibiotics do not clear the infection so many cats become carriers of the organism however relapses are uncommon.
References
Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2)W.B. Saunders Company
Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial