Abstract

Many species of mammals, birds, and ticks are reservoirs of Coxiella burnetii, the cause of Q fever in humans, but ruminant species are the predominant zoonotic source. Animals infected with C. burnetii can be asymptomatic. This retrospective study evaluated prevalence of Coxiella burnetii in placentas obtained from 88 animals representing 32 different ungulate species between 1993 and 2007 from seven different zoos, and in two known positives from one of the facilities. Tissues were from normal births, abortions, or stillbirths in which C. burnetii was not considered the main differential diagnosis. Archived paraffin-embedded tissues were examined for microscopic lesions and for DNA from C. burnetii, using a real-time PCR assay. Infection was confirmed by immunohistochemistry. The PCR assay detected C. burnetii in placental tissues from four additional animals: two bongos (Tragelaphus eurycerus), a Cuvier’s gazelle (Gazella cuvieri), and an Indochinese sika (Cervus nippon pseudaxis), as well as the two known positives, a Malayan sambar (Rusa unicolor equine) and a Javan rusa (Rusa timorensis rusa); all cases were from one of the seven facilities. Histology showed mild to severe necrotizing placentitis in all infected placentas. Immunohistochemistry demonstrated organisms within the trophoblast cells and free within the overlying necrotic debris. Evaluating C. burnetii prevalence in the zoological environment may aid in determining the potential for occupational exposure and aid in the design of biosafety training of zoo employees in contact with infected animals. This study also highlights the value of ancillary testing which may not have been previously available (such as PCR) in the diagnosis of C. burnetii even in healthy births or from grossly normal placentas.