Q fever in patients with hepatitis and pneumonia: results of laboratory-based surveillance in the United States

Q fever in members of the United States armed forces returning from Iraq

Large numbers of armed forces personnel returning from southwest Asia may present with infections that are not endemic to the United States or that occur rarely and are underdiagnosed in the United States. We report 2 cases of acute Q fever in members of the US Military recently returned from Iraq. Because a number of recent reports suggest that the risk of Q fever may be higher than initially thought among US forces deployed to this region, clinicians need to have a high index of clinical suspicion, an understanding of the available diagnostic tests, and knowledge regarding the methodology and capabilities of the laboratory to which specimens are submitted.

Chronic Q fever in the United States

Infections due to Coxiella burnetii, the causative agent of Q fever, are uncommon in the United States. Cases of chronic Q fever are extremely rare and most often manifest as culture-negative endocarditis in patients with underlying valvular heart disease. We describe a 31-year-old farmer from West Virginia with a history of congenital heart disease and recurrent fevers for 14 months who was diagnosed with Q fever endocarditis based on an extremely high antibody titer against Coxiella burnetii phase I antigen. Despite treatment with doxycycline, he continued to have markedly elevated Coxiella burnetii phase I antibody titers for 10 years after the initial diagnosis. To our knowledge, this case represents the longest follow-up period for a patient with chronic Q fever in the United States. We review all cases of chronic Q fever reported in the United States and discuss important issues pertaining to epidemiology, diagnosis, and management of this disease.

Q fever in humans and animals in the United States

Coxiella burnetii, the etiologic agent of Q fever, is a worldwide zoonotic pathogen. Although Q fever is present in the United States, little is known about its current incidence or geographic distribution in either humans or animals. Published reports of national disease surveillance, individual cases, outbreak investigations, and serologic surveys were reviewed to better characterize Q fever epidemiology in the United States. In national disease surveillance reports for 1948-1986, 1,396 human cases were reported from almost every state. Among published individual case reports and outbreak investigations, occupational exposures (research facilities, farm environments, slaughterhouses) were commonly reported, and sheep were most frequently implicated as a possible source of infection. In studies conducted on specific groups, livestock handlers had a significantly higher prevalence of antibodies to C. burnetii than did persons with no known risk. Animal studies showed wide variation in seroprevalence, with goats having a significantly higher average seroprevalence (41.6%) than sheep (16.5%) or cattle (3.4%). Evidence of antibody to C. burnetii was reported among various wild-animal species, including coyotes, foxes, rodents, skunks, raccoons, rabbits, deer, and birds. This literature review suggests that C. burnetii is enzootic among ruminants and wild animals throughout much of the United States and that there is widespread human exposure to this pathogen. Sheep and goats appear to be a more important risk for human infection in the United States than cattle or wild animals, and research studies examining the natural history and transmission risk of Q fever in sheep and goats in this country should be encouraged.

Q fever

Q fever is a zoonosis with a worldwide distribution with the exception of New Zealand. The disease is caused by Coxiella burnetii, a strictly intracellular, gram-negative bacterium. Many species of mammals, birds, and ticks are reservoirs of C. burnetii in nature. C. burnetii infection is most often latent in animals, with persistent shedding of bacteria into the environment. However, in females intermittent high-level shedding occurs at the time of parturition, with millions of bacteria being released per gram of placenta. Humans are usually infected by contaminated aerosols from domestic animals, particularly after contact with parturient females and their birth products. Although often asymptomatic, Q fever may manifest in humans as an acute disease (mainly as a self-limited febrile illness, pneumonia, or hepatitis) or as a chronic disease (mainly endocarditis), especially in patients with previous valvulopathy and to a lesser extent in immunocompromised hosts and in pregnant women. Specific diagnosis of Q fever remains based upon serology. Immunoglobulin M (IgM) and IgG antiphase II antibodies are detected 2 to 3 weeks after infection with C. burnetii, whereas the presence of IgG antiphase I C. burnetii antibodies at titers of >/=1:800 by microimmunofluorescence is indicative of chronic Q fever. The tetracyclines are still considered the mainstay of antibiotic therapy of acute Q fever, whereas antibiotic combinations administered over prolonged periods are necessary to prevent relapses in Q fever endocarditis patients. Although the protective role of Q fever vaccination with whole-cell extracts has been established, the population which should be primarily vaccinated remains to be clearly identified. Vaccination should probably be considered in the population at high risk for Q fever endocarditis.

Q-fever and autoimmunity

STUDY OBJECTIVE

To determine the incidence and the clinical significance of two autoimmune markers in Q-fever (smooth muscle antibodies, cold agglutinins).

DESIGN

Six index cases with auto-immune disorders. Assays of 104 sera from patients with Q-fever (including index cases) using immunofluorescence for smooth muscle antibodies, microagglutination for cold agglutinins.

SETTING

French National Reference Center for Rickettsial Diseases.

CASES

6 patients were studied with acute Q-fever and auto-immune disorders. 3 of whom had presented a resistance to a therapy with antibiotics. Stored samples from other patients with acute or chronic stage were also screened to appreciate the incidence of the two markers.

MEASUREMENTS AND MAIN RESULTS

CASE REPORTS

No correlation between Q-fever and smooth muscle antibodies titers and kinetics were found. A spurt of corticosteroids was necessary to obtain apyrexia for the patients who had presented multiple auto-immune disorders and a resistance to the classical therapy. INCIDENCE; Smooth muscle antibodies were detected in 27%, cold agglutinins in one case. They were present in 23% of the patients with acute cases and in 38% with chronic stage.

CONCLUSION

The incidence of auto-immune disorders is unexpectedly high and could explain some manifestations of acute Q-fever e.g the resistance to therapy with antibiotics which are not yet clear. Then the association during the acute stage of auto-immune disorders with the persistence of clinical or biological findings after three weeks therapy could recommend the use of corticosteroids.