Emerging tick-borne bacterium threatens immunocompromised patients

An emerging tick-borne bacterium in Europe, Asia, and Africa poses a risk for immunocompromised patients, causing an illness that could be mistaken for an underlying disease, according to a study published yesterday in Clinical Infectious Diseases.

The bacterium, widespread in ticks, rats, mice, and voles, was discovered in Japan in 2004 and was first recognized as a human pathogen in 2010, says the report by a European team. It is called Candidatus Neoehrlichia mikurensis, with the first term signifying that no one has reported cultivating it as yet.

The authors gathered data on 11 European patients with hematologic malignances or autoimmune diseases in whom the infection was diagnosed from 2010 to 2013.

The patients were mostly older men (median age, 67); all but one had ongoing or recent immunosuppressive treatment, and 8 of 11 had undergone splenectomy, the report says. Less than half of them recalled tick exposure.

The most frequent symptoms were fever (in 11 of 11), pain in muscles and/or joints (8 of 11), vascular and thromboembolic events such as deep vein thrombosis (6 of 11), transitory ischemic attacks (2), pulmonary embolism (1), and arterial aneurysm (1).

The median time from first symptoms to correct diagnosis was 2 months. In at least four cases, the condition was attributed to the underlying disease, and immunosuppressive therapy was scheduled. All the patients recovered with doxycycline treatment.

The authors conclude that Ca Neoehrlichia mikurensis is “an emerging tick-borne pathogen that may give rise to a systemic inflammatory syndrome in persons with hematologic or autoimmune diseases that could be mistaken for recurrence of the underlying disease and/or unrelated arteriosclerotic vascular events. Awareness of this new pathogen is warranted among rheumatologists, hematologists, oncologists, and infectious disease specialists.”



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