A bird seller developed fever with chills and severe body pain. Investigation confirms the disease as ornithosis. Causative agent is:

Psittacosis (parrot fever, parrot disease, or ornithosis) is caused by C. psittaci (formerly Chlamydia psittaci), an organism common to most birds and domesticated fowl. Human acquisition is from the inhalation of dust from dried bird feces, feather dust, or aerosolized an respiratory secretions. Psittacosis is characterized by an incubation period of 5 to 14 days followed by abrupt onset of fever, chills, cephalgia, myalgia, and generalized malaise. Melioidosis is a potentially serious illness caused by the gram-negative, saprophytic bacterium Burkholderia pseudomallei (formerly Pseudomonas pseudomallei). The agent of Q fever is Coxiella burnetii, a small intracellular microorganism that only recently was grown in cell-free medium. C. burnetii, a pleomorphic coccobacillus with a gram-negative cell wall. Relapsing fever is a vector-borne disease caused by spirochetes of the genus Borrelia. Ref: Brooks G.F., Carroll K.C., Butel J.S., Morse S.A., Mietzner T.A. (2013). Chapter 27. Chlamydia Spp.. In G.F. Brooks, K.C. Carroll, J.S. Butel, S.A. Morse, T.A. Mietzner (Eds), Jawetz, Melnick, & Adelberg's Medical Microbiology, 26e.