Q fever at the turn of the century.

Q fever is an infectious zoonotic disease characterized by sudden fever, headache, and atypical pneumonia, caused by Coxiella burneti--an obligatory intracellular parasite. Based on phylogenetic analysis of the genes sequences, the classification was changed and C. burnetii species was included to the gamma subgroup of the proteobacteria, Legionellales order and Coxiellaceae family. This analysis showed more than 99% sequence similarity of 16SrRNA gene among the strains isolated in different regions of the world. Q fever is a widespread in the world zoonosis. Its main reservoir in the rural environment are farm animals: cows, sheep, goats, and urban pets such as dogs, cats, rabbits. In acute infection these bacteria are detected in various internal organs such as lungs, liver, spleen, and in excretion in urine, faeces and milk. During childbirth, they occur in large number in the amniotic fluid and placenta. Recently, it has been found that free-living amoeba Acanthamoeba castellani may also be a reservoir of the pathogen. The intra-amoebal location of C. burnetii cells was observed.