An acute severe ehrlichiosis in a dog experimentally infected with a new virulent strain of Ehrlichia canis.

Canine monocytic ehrlichiosis (CME) is caused by Ehrlichia canis, an obligate intracellular bacterium with tropism for monocytes and macrophages. It is transmitted by the ticks Rhipicephalus sanguineus and Dermacentor variabilis. CME has been reported throughout the world, with a higher frequency in tropical and subtropical regions. The disease may be manifested by fever, depression, dyspnoea, anorexia, haemorrhages, oedema and weight loss accompanied with laboratory findings of thrombocytopenia, leukopenia, anaemia, and hypergammaglobulinaemia [1–5]. It has been reported that experimental infection of dogs with a cell culture-passaged type strain of E. canis Oklahoma induces mild clinical signs and mild pathological alterations in dogs [4]. Therefore, an acute severe experimental canine infection model is needed to study the pathological and immunological pathways induced by virulent E. canis. The purpose of the present study was to describe the experimental infection of a dog with a virulent strain of E. canis (New Mexico) by analysing haematological and pathological findings.