Subclinical chronic Q fever

Seven patients are described in whom chronic Q fever was detected by serology (Coxiella burneti phase I antibody titre greater than 1:200) during routine screening at admission for cardiac catheterisation. None had clinical evidence of endocarditis, hepatitis or other foci of infection. Three of the patients were kept under observation without antibiotic treatment for periods of six, 18 and 20 months. In two patients of this group, cardiac tissue was obtained at operation and in one patient seroconversion following guinea-pig inoculation indicated the presence of Coxiella burneti infection. Four patients were given antibiotic treatment when Q fever was confirmed by serology. Courses of antibiotic treatment with a combination of two drugs were maintained for four to six years and in three of these patients phase I antibody titres fell to very low levels with no appearance of overt infection. The fourth patient died after resection of an aortic aneurysm, seven months after starting antibiotic treatment. Cases reported in the literature indicate that while endocarditis is the most common manifestation of chronic Q fever, the infection can persist at other sites. Of the seven cases of subclinical chronic Q fever reported here, the infection was localised in only one. Patients with this subclinical form of infection pose the therapeutic dilemma of whether or not they should receive antibiotic treatment.