Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 32-13: Other Rickettsial & Rickettsial-Like Diseases + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ Exposure to sheep, goats, cattle; some laboratory-acquired infections Acute or chronic febrile illness: headache, cough, prostration, and abdominal pain Pneumonitis, hepatitis, or encephalopathy; less often, vascular infections or chronic fatigue syndrome A common cause of culture-negative endocarditis +++ General Considerations ++ Q fever, a reportable and significantly underestimated disease in the United States, is caused by the gram-negative intracellular coccobacillus Coxiella burnetii Human infection occurs via inhalation of aerosolized bacteria (in dust or droplets) from feces, urine, milk, or products of conception of infected animals Ingestion and skin penetration are other recognized routes of transmission There is a known occupational risk for animal handlers, slaughterhouse workers, veterinarians, laboratory workers, and other workers exposed to animal products In the United States, over 60% of cases do not report an exposure to potentially infectious animals; drinking raw milk may be an infectious exposure Human-to-human transmission does not seem to occur, but maternal-fetal infection can occur Infection post-liver transplant has been reported Chronic Q fever is now termed "persistent focalized infections" + Clinical Findings Download Section PDF Listen +++ ++ Asymptomatic infection is common For the remaining cases, a febrile illness develops after an incubation period of 2–3 weeks, usually accompanied by headache, relative bradycardia, prostration, and muscle pains Clinical course may be acute, chronic (duration 6 months or longer), or relapsing Pneumonia and granulomatous hepatitis are the predominant manifestations in the acute form Less common manifestations include Skin rashes (maculopapular or purpuric) Fever of unknown origin Myocarditis Pericarditis Aortic aneurysms Aseptic meningitis Encephalitis Orchitis Iliopsoas abscess Spondylodiscitis Tenosynovitis Granulomatous osteomyelitis (more often seen in children) Regional (mediastinal) Diffuse lymphadenopathies Culture-negative endocarditis is most common presentation in patients with persistent focalized infections Risk factors include Immunocompromised state Preexisting valvular conditions Male sex Age above 40 years Valvular prosthesis (mechanical or bioprosthesis) Clinical manifestations of endocarditis are nonspecific with fever, night sweats, and weight loss Sudden cardiac insufficiency, stroke, or other embolic and mycotic aneurysms can develop Rarely, urticaria, edema, erythema nodosum, and arthralgias are reported New infection or reactivation of Q fever can occur in pregnant women and is associated with Spontaneous abortions Intrauterine growth retardation Intrauterine fetal death Premature delivery Oligohydramnios (when infection occurs during first trimester) +++ Differential Diagnosis ++ Viral, mycoplasmal, and bacterial pneumonias Viral hepatitis Brucellosis Legionnaire disease Murine or scrub typhus Kawasaki disease Tuberculosis Psittacosis + Diagnosis Download Section PDF Listen +++ +++ Laboratory Findings ++ Elevated liver biochemical tests Leukocytosis A fourfold rise between acute and convalescent sera by indirect immunofluorescence is diagnostic of the infection Real-time PCR for C burnetii DNA is helpful only in early stage of infection Diagnostic tests using Immuno-PCR and combining PCR with ELISA improve the sensitivity and specificity during the first 2 weeks after the onset of symptoms An automated epifluorescence assay has > 95% sensitivity for the detection of phase I antigens in persistent infection Phase variation is the change that occurs in the outer lipopolysaccharide membrane of the Coxiella burnetii with chronicity of infection Acute infection usually has higher phase II antibodies than phase I antibodies C burnetii-specific interferon-gamma, interferon-gamma/IL-2 ratio has a sensitivity of 79% and a specificity and 97% for the diagnosis of persistent infection +++ Imaging ++ Radiographs of the chest can show patchy pulmonary infiltrates Echocardiography should be done in all patients with acute Q fever to screen for underlying valvular disease Initial imaging and follow-up with serial 18-FDG PET/CT scan may be helpful in identifying chronic infection and monitoring treatment response + Treatment Download Section PDF Listen +++ ++ For acute infection, doxycycline (100 mg orally twice daily) for 14 days or at least 3 full days after defervescence is recommended For native valve endocarditis and prosthetic valve endocarditis, most experts recommend a combination oral therapy with doxycycline (100 mg twice a day) plus quinolone or rifampin or hydroxychloroquine for approximately 18 months and 24 months, respectively For patients with endocarditis, clinical cure is possible without valve replacement All infected pregnant women should be given long-term trimethoprim-sulfamethoxazole (320/1600 mg orally for the duration of pregnancy but not beyond 32 weeks' gestation) + Outcome Download Section PDF Listen +++ +++ Complications ++ Patients with persistent focalized infections may have higher risk for lymphadenitis and progression to diffuse B-cell lymphoma and follicular lymphoma +++ Follow-Up ++ Patients should be monitored for at least 5 years due to risk of relapse +++ Prevention ++ Prevention is based on detection of the infection in livestock, reduction of contact with infected and parturient animals or contaminated dust; special care when working with animal tissues; and effective pasteurization of milk A whole-cell Q fever vaccine is available in Australia for persons with high-risk exposures, although there are reports of vaccine failure more than 15 days after vaccination C burnetii is a category B bioterrorism agent; in the setting of a bioterrorist attack, Postexposure prophylaxis with doxycycline 100 mg orally twice a day for 5–7 days should be started 8–12 days after exposure Pregnant women may take trimethoprim-sulfamethoxazole as an alternative +++ Prognosis ++ Mortality rate is usually low (even in untreated patients), except when endocarditis develops + References Download Section PDF Listen +++ + +Alonso E et al. A Q fever outbreak associated to courier transport of pets. PLoS One. 2019 Nov 25;14(11):e0225605. [PubMed: 31765433] + +Eldin C et al. From Q fever to Coxiella burnetii infection: a paradigm change. Clin Microbiol Rev. 2017 Jan;30(1):115–90. [PubMed: 27856520] + +Gerlach C et al. Coxiella burnetii immunogenic proteins as a basis for new Q fever diagnostic and vaccine development. Acta Virol. 2017;61(3):377–90. [PubMed: 28854806] + +Jang YR et al. Molecular detection of Coxiella burnetii in heart valve tissue from patients with culture-negative infective endocarditis. Medicine (Baltimore). 2018 Aug;97(34):e11881. [PubMed: 30142785] + +Mboussou Y et al. Pregnancy outcomes of Q fever: prospective follow-up study on Reunion island. BMC Infect Dis. 2019 Nov 27;19(1):1001. [PubMed: 31775645] + +Million M et al. No such thing as chronic Q fever. Emerg Infect Dis. 2017 May;23(5):856–7. [PubMed: 28418317] + +Straily A et al. Surveillance for Q fever endocarditis in the United States, 1999–2015. Clin Infect Dis. 2017 Nov 13;65(11):1872–7. [PubMed: 29140515]