A 33-year-old man presents at OPD complaining of fever and headache. On examination, he had leukopenia and increased liver enzymes, and inclusion bodies were seen in his monocytes. History revealed that he went on camping and remembered removing a tick from his leg. Which of the following diseases is most likely causing the symptoms described?

All the listed diseases except Q fever are tick-borne. The rickettsia C. burnetii causes Q fever, and humans are usually infected by aerosol of a sporelike form shed in milk, urine, feces, or placenta of infected sheep, cattle, or goats. Lyme disease is caused by a spirochete, Borrelia burgdorferi, and produces the characteristic lesion erythema chronicum migrans (ECM). The etiologic agent of Rocky Mountain spotted fever is R. rickettsia. It usually produces a rash that begins in the extremities and then involves the trunk. Two human forms of ehrlichiosis can occur: human monocytic ehrlichiosis (HME), caused by E. chaffeensis; and human granulocytic ehrlichiosis (HGE), caused by an as yet unnamed Ehrlichia. HME infection is transmitted by the brown dog tick and A. americanum. HGE infection is transmitted by I. scapularis, the same tick that transmits Lyme disease. Both infections cause fever and leukopenia. A rash rarely occurs. E. chaffeensis infects monocytes, and HGE infects granulocytes; both organisms produce inclusion bodies called morulae. Francisella tularensis is a small, Gram-negative, nonmotile coccobacillus. Humans most commonly acquire the organism after contact with tissues or body fluid of an infected mammal or the bite of an infected tick.