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Introduction: Bartonella henselae, the agent of cat scratch disease, has previously been char-acterized in its reservoir host, the domestic cat. As fleas are the main vectors for transmission among cats, the prevalence of B. henselae infections is high in animal shelters and in popula-tions of stray cats. In humans infected with B. henselae, the course of disease differs greatly between immunocompetent and immunocompromised patients: while the former develop the generally self-limiting cat scratch disease, the latter may develop serious conditions including septicaemia, bacillary angiomatosis and peliosis hepatis. Although peliosis hepatis is com-monly found in cats, there are no studies yet linking the condition in cats to an infection with B. henselae or comparing the prevalence and pathogenicity of B. henselae infections in im-munocompetent cats with that in cats suffering from immunocomprimising conditions.
Material and methods: Blood samples and a wide range of tissues from 88 cats from animal shelters were examined for B. henselae using PCR and immunohistochemistry. In addition, liver specimens from nine cats with peliosis hepatis were retrospectively screened for the presence of B. henselae.
Results: 51 out of 88 cats were classified as suffering from potentially immunocompromising conditions, e.g. cachexia, panleukopenia or FeLV infection (group A). 37 cats showed no evidence of such conditions (group B). Of the immunocompromised group, five cats tested positive for B. henselae in at least one organ (9, 8 %), compared to three cats (8, 1 %) in the immunocompetent group. B. henselae was primarily detected in lymphatic tissues or bone marrow, with or without bacteraemia. The bacteria were not detected in any of the liver specimens with peliosis hepatis, neither by PCR nor by immunohistochemistry.
Discussion: In contrast to the situation in humans, this study failed to reveal significant dif-ferences between the prevalence, pathogenicity and organ lesions of B. henselae infections in cats with potentially immunocomprimising conditions compared to cats without such condi-tions. However, the actual presence or degree of immunodeficiency in group A cats could not be unequivocally established. Finally, no causative link was established between B. henselae infection and feline peliosis hepatis, again contrary to the human disease.