Guinea Pig Aerosol Challenge Presents New Model For Q Fever Research In Humans

Q fever, caused by the bacterium Coxiella burnetti, generally infects humans through inhalation with as few as 10 organisms capable of causing disease. C. burnetti has a high degree of resistance to treatment agents and can remain infectious in contaminated soils for years. Due to its highly infectious nature, the Centers for Disease Control and Prevention has listed C. burnetti as a potential weapon of mass destruction reinforcing the need for a safe and effective vaccine. There is currently no licensed vaccine available in the U.S.

In the study select guinea pigs received a killed whole-cell Q fever vaccine after which all were infected with C. burnetti through inhalation of small-particle aerosols and evaluated 28 days postinfection. Noted clinical signs included fever, weight loss, respiratory difficulty and death with the degree and duration of response correlating with the dose of organism delivered. Those guinea pigs vaccinated prior to challenge with the highest dose of C. burnetti did not develop fever and were protected against lethal infection.

"The guinea pig aerosol challenge model presented here mimics both the clinical and pathologic changes seen in human acute Q fever and Q fever pneumonia cases and will provide an accurate and valuable tool for the study of the general pathogenesis of C. burnetti infection, for vaccine assessment, and for evaluations of host immune responses," say the researchers.

(K.E. Russell-Lodrigue, G.Q. Zhang, D.N. McMurray, J.E. Samuel. 2006. Clinical and pathological changes in a guinea pig aerosol challenge model of acute Q fever. Infection and Immunity, 74. 11: 6085-6091.)