Officially named in 2004, Candidatus Neoehrlichia mikurensis is an obligate intracellular, gram-negative bacterium. The pathogen is characterised by endotheliotropism but has not been cultivated in vitro so far and thus could not be completely described yet.
Cand. N. mikurensis was first found in common rats on the Japanese island of Mikura. It is assumed that small mammals, such as mice and rats, serve as reservoir; transmission most likely occurs through ticks. In recent years, Cand. N. mikurensis has been detected in about 2 to 25% of Ixodes ricinus ticks in Germany.
Since 2007, this pathogen has been associated with diseases in humans. Especially the elderly and immunocompromised people have been affected by the so-called neoehrlichiosis, including two patients from Germany. The symptoms are non-specific, most often high fever and headaches as well as muscular pain and joint pains were seen. The occurrence of vascular complications, like deep vein thromboses, pulmonary embolism and arterial aneurysms, was most noticeable. Laboratory findings particularly indicate an increased level of C-reactive protein, leukocytosis with neutrophilia and anaemia.
In dogs, so far only one single case has been reported in which this bacterium could be isolated. It was an eight-year old female Irish Setter after ovariohysterectomy and mastectomy. Postoperatively, she was lethargic and developed profuse subcutaneous bleeding (Diniz et al. 2011).