Evaluation of cynomolgus (Macaca fascicularis) and rhesus (Macaca mulatta) monkeys as experimental models of acute Q fever after aerosol exposure to phase-I Coxiella burnetii.

Background and purpose: Q fever is a disease of humans. Vaccines to prevent this disease have demonstrated efficacy in rodents and must also be evaluated for efficacy in a nonhuman primate model. Preliminary to vaccine efficacy experiments, cynomolgus and rhesus monkeys were evaluated as suitable experimental models of acute Q fever.

Methods: Both species of monkeys were challenged with aerosolized 10(5) virulent phase-I Coxiella burnetii Henzerling strain, and clinical and serologic responses were determined.

Results: Radiographic changes were observed in seven of eight monkeys of both species; however, changes in cynomolgus monkeys tended to be more significant. Between 7 and 10 days after challenge, all rhesus monkeys and 88% of cynomolgus monkeys were bacteremic. Sequential increases in antibody responses to C. burnetii phase-I and phase-II whole cells and phase-I lipopolysaccharide were observed in both species. Although the maximal rectal temperature increase was similar in both species, duration of fever was slightly longer in rhesus monkeys. Clinical features were similar to those described in human acute Q fever patients.

Conclusions: On the basis of the more pronounced radiographic changes in cynomolgus monkeys, we favor use of this species for future studies of vaccine efficacy.