Coxiella burnetii penetration into the reproductive system of male mice, promoting sexual transmission of infection.

Coxiella burnetii bacteria penetrate different host organs via the bloodstream. In infected mice, bacteremia was observed during the first week of infection: later, bacteria were cultured from the spleens, livers, testes, epididymes, prostate, and semen; bacteriuria developed beginning from the second week of infection. On day 21 of infection, degenerative changes with aggregated macrophages containing bacteria were observed in capillary blood vessels and the surrounding tissues of the adipose envelope of the epididymis. C. burnetii was shed to semen from the urogenital tract, probably from an abscess in the epididymis. There they were bound to the surface of spermatozoal cells, mainly to their heads, suggesting specific adhesion. Bacteria shed to semen were transmitted to female mice by sexual contact; this was demonstrated by the detection of antibodies against C. burnetii antigens in the blood of females and later by the cultivation of bacteria from the spleens, livers, and amniotic fluids of female mice.