Generally associated with subclinical disease in cats, hemolytic anemia is a consequence of several human Bartonella spp.
infections, including a case of human hemolytic anemia caused by Bartonella henselae. Studies have also demonstrated the intraerythrocytic
location of B. henselae in naturally-infected cats. However, an epidemiologic study attempting to correlate various organisms,
through the use of PCR assays, with cases of hemolytic anemia found no significant prevalence differences in the healthy cats
versus anemic cats with a positive Bartonella PCR assay.
Ehrlichia spp. has been demonstrated to cause clinical signs in cats, including fever, lethargy, inappetence and anemia. The
anemia is often classified as non-regenerative. However, because Ehrlichia PCR is not normally part of the battery of infectious
disease tests ordered for the cat with hemolytic anemia, it is still not known how much of a role this disease plays.
A non-regenerative anemia is usually the clinicopathologic abnormality in young cats diagnosed with FeLV, but hemolytic anemias
have been documented. FeLV antigen testing is therefore recommended for any cat presenting with hemolytic anemia. FIV infectious
are nearly always associated with a non-regenerative anemia and likely falls into the category of "anemia of chronic disease"
rather than a primary immune-mediated mechanism.
Primary Immune-mediated Disease
There is a subset of cats for which neoplasia, toxins and the majority of infectious diseases have been ruled out, either
by infectious disease assays or trial therapies with anti-bacterial agents. These cats only respond to immunosuppressive doses
of glucocorticoids and have relapses when dosages are reduced or discontinued. Primary IMHA has been thought to be uncommon
in cats, but recent epidemiologic studies and case series suggest. IN one retrospective study, approximately 60% of cats with
anemia had no identifiable infectious or neoplastic cause for their anemia. New techniques, such as flow cytometry and anti-erythrocyte
antibody assays, may be helpful in identifying cats with an underlying primary hemolytic anemia.
The most common cause of hemolytic anemia in cats has long thought to be secondary to infectious diseases, neoplasia, and
toxins. While these infectious and non-infectious diseases should be considered in cats presenting with hemolytic anemia,
primary hemolytic anemia may be more common in these cats than historically thought.
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