Case 209. Ehrlichiosis (adult dog)
　 　 　 　 　
　 　
Peripheral blood smear of the dog infected with Ehrlichia canis
 　 　
　 　 　 　 　
　 　
Key words : 
 Ehrlichia canis, monocytic ehrlichiosis, Q fever, Coxiella burnetti 　 　
　 　 　 　 　
　 　
zoonosis
 　 　
　 　 　
　
　 　 　
The monocyte contains a cluster of fine granules of infected E. canis in the cytoplasm (Giemsa). E. canis is not pathogenic to human. Ehrlichiosis is transmitted by tick bite. 　 Another view of E. canis-infected canine monocyte (Giemsa). In human, human monocytic ehrlichiosis caused by E. chaffeensis and human granulocytic ehrlichiosis caused by E. phagocytophila are known as emerging infectious diseases.
　 　 　
　
　 　 　
Coxiella burnetti in a mouse splenic macrophage (Gimenez)
C. burnetti, a causative agent of Q fever, is an obligate intracellular Gram-negative bacterium. Ticks transmit the microbes to animals. Human infection is mainly tranmitted by droplets containing Coxiella of animal origin.　Q fever is often presented as atypical pneumonia, accompanying influenza-like signs and symptoms. This zoonotic pathogen of rickettsia group is resistant to heat, dryness and disinfectant, so that it is nominated as a bioterrorist.		 　 Electron micrograph of Coxiella burnetti in mouse splenic macrophages
Small rods are clustered within the cytoplasm of macrophages to form cytoplasmic inclusions.　Chronic Q fever shows features of endocarditis, chronic hepatitis or chronic osteomyelitis. Small epithelioid granuloma (fibrin ring granuloma) is a histologic hallmark of the liver lesion.
　 　 　
　
　 　 　
Electron micrograph of Coxiella burnetti in a mouse splenic macrophage
Morphology and electron density of C. burnetti in phagosomes of a macrophage are varied.　C. burnetti is an exceptional rickettsia, in that it does not necessarily require the anthropod vector for transmission.