Several employees in a veterinary facility experience a mild influenza-like infection after working on six sheep with an undiagnosed illness. The etiologic agent causing the human disease is most often transmitted to humans by which of the following methods?

Coxiella burnetii is a rickettsial organism that causes upper respiratory infections in humans. These can range from sub-clinical infection to influenza-like disease and pneumonia. Transmission to humans occurs from inhalation of dust contaminated with rickettsiae from placenta, dried feces, urine, or milk, or from aerosols in slaughterhouses. Campylobacter burnetii can also be found in ticks, which can transmit the agent to sheep, goats, and cattle. No skin rash occurs in these infections. Treatment includes tetracycline and chloramphenicol. Coxiella burnetii is not transmitted by flea or tick vectors. Since Q fever involves the upper respiratory tract, liver, or CNS, there is no transmission by urethral discharge.