AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

First described in Australia in 1935, Q fever is a rickettsial disease with acute and chronic stages. Q fever differs from other rickettsial diseases in that it is caused by inhalation of infected particles, not by a tick bite. Because Q fever is transmitted via an inhalational route, it can be used as a biological warfare agent. The Centers for Disease Control and Prevention (CDC) classifies Q fever as a Category B agent.

Pathophysiology

The respiratory system is the main organ system affected, although GI and cardiac systems also are affected. Incubation period varies from 9-40 days, with an average range of 18-21 days.

Frequency

United States

Frequency is difficult to ascertain even though Q fever is a reportable disease in all US states except Delaware, Iowa, Oklahoma, Vermont, and West Virginia. In 2005, 136 cases were reported to the CDC; in 2006, 169 cases were reported. Dairy and slaughterhouse workers are most at risk. In 2006, the incidence was reported to be 0.06 per 100,000 population.

International

Incidence of Q fever is worldwide and varies in frequency and presentation from country to country. A recent outbreak occurred in the Netherlands in 2008.¹ From January to July, 660 cases have been reported. This is the second outbreak to occur in the Netherlands since 2007. At this time, the cause is still unknown.

Mortality/Morbidity

The mortality rate with acute infection is reportedly as high as 2.4% but generally is less than 1%.

Sex

Males are affected more than females. Of the 169 cases reported to the CDC in 2006, 127 were in males and 42 were in females.

Age

Adults are affected more than children. The highest age range is between 40 and 64 years.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

• Patients initially present with influenzalike symptoms.
• Respiratory symptoms appear 4-5 days after initial onset of illness (most prominently a dry nonproductive cough and pleuritic chest pain).
• Symptoms of Q fever include the following:
• • Fever
  • Severe headache
  • Myalgias
  • Anorexia
  • Cough
  • Pleuritic chest pain
  • Sweats
  • Chills
  • Nausea, vomiting, and diarrhea (rare)

Physical

Often in acute Q fever, specific findings may not exist. In chronic Q fever, findings consistent with endocarditis and hepatitis more frequently are found.

• Findings in endocarditis include the following:
• • Vegetations on any valve (although aortic and prosthetic valves are favored)
  • Clubbing of digits
  • Hepatomegaly and splenomegaly in approximately one half of patients
  • Arterial emboli in approximately one third of patients
  • Purpuric rash in approximately 20% of patients
• Findings in hepatitis include the following:
• • Fever
  • Malaise
  • Hepatomegaly with right upper quadrant pain
  • Jaundice (occasional)
• Aseptic meningitis/encephalitis occurs in approximately 1% of acute and chronic Q fever cases.

Causes

Coxiella burnetii, a pleomorphic coccobacillus that is much smaller than other rickettsias, is the etiologic agent of Q fever. Humans are infected by inhalation of C burnetii. Why chronic Q fever develops in certain patients is unknown.

• Q fever is extremely virulent; 1 bacterium can cause infection.
• Q fever is extremely resistant to inactivation; it can survive for months in dust and feces particles.
• Tick species, naturally infected, infect domestic and small mammals (eg, cats).
• C burnetii localizes in the mammary glands, uterus, and feces of these animals. Exposure to feces can lead to disease.
• Laboratory outbreaks have occurred. Only 1 case of documented human-to-human transmission exists.
• C burnetii exists in 2 antigenic states, phase I (virulent) and phase II (avirulent).

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Acute Q fever
• • Complete blood count is normal in 70% of patients with acute Q fever, but an elevated white blood count (WBC) is present in 30% of patients.
  • Liver function tests often show a slight elevation (2-3 times) of transaminases, but bilirubin usually is normal.
  • Serologic tests are not helpful acutely but later may confirm diagnosis. The indirect immunofluorescence assay (IFA) is the most dependable and widely used serologic method. ELISA tests are also becoming more widely available. A 4-fold rise in complement-fixing antibody titer against phase II antigen occurs. This requires a baseline sample and another sample in 3-4 weeks.
• Chronic Q fever
• • Serologic testing
  • Complement-fixing antibody titer against phase I antigen of greater than or equal to 1:200, or phase I immunoglobulin A (IgA) or immunoglobulin G (IgG) greater than or equal to phase II titer
  • Culture-negative endocarditis
  • Granulomas on liver biopsy
  • Cerebral spinal fluid findings are consistent with aseptic meningitis (eg, elevated WBC with mainly monocytes, elevated protein, normal glucose, negative Gram stain)

Imaging Studies

• Acute Q fever
• • The chest radiograph is variable (normal-to-widespread pneumonitis).
  • The hepatic ultrasonogram may show granulomatous hepatitis.
• Chronic Q fever
• • The echocardiogram most commonly depicts endocarditis of aortic valve. Abnormal and prosthetic valves are also prone to being affected.
  • The hepatic ultrasonogram shows granulomatous hepatitis.

Procedures

• Perform lumbar puncture if Q fever meningoencephalitis is suspected.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Emergency Department Care

• Recognize disease and start appropriate antibiotic therapy.
• Provide supportive care.

Consultations

Consult infectious disease, especially if chronic Q fever is suspected.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Antibiotics are necessary for acute and chronic Q fever. However, in chronic Q fever, exact antibiotics recommended for use are in a state of flux. Consult infectious disease prior to starting antibiotics in this situation. Best studied are combinations of doxycycline plus an additional antibiotic (eg, fluoroquinolone, rifampin, trimethoprim-sulfamethoxazole).

Drug Category: Antibiotics

Therapy must cover all likely pathogens in the context of the clinical setting.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Valve replacement may be required, depending on cardiac status.

Further Outpatient Care

• For acute Q fever, antibiotic therapy should last 10-14 days.
• For chronic Q fever, antibiotic therapy lasts a minimum of 2 years.

Deterrence/Prevention

• Identify infections in domesticated animal populations.
• Birthing should take place in indoor facilities.
• Properly dispose of placentae, fetal membranes, and aborted material.
• Human Q fever vaccine is available in Australia and Eastern Europe but not in the US.

Prognosis

• Acute Q fever, if properly diagnosed and treated, has very low morbidity and mortality.
• Chronic Q fever requires long-term antibiotic therapy including close follow-up care with an infectious disease specialist.

Patient Education

• For excellent patient education resources, visit eMedicine's Bioterrorism and Warfare Center. Also, see eMedicine's patient education articles Biological Warfare and Personal Protective Equipment.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Obtain an occupational history from patients.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

1. Schimmer B, Morroy G, Dijkstra F, Schneeberger PM, Weers-Pothoff G, Timen A, et al. Large ongoing Q fever outbreak in the south of The Netherlands, 2008. Euro Surveill. Jul 31 2008;13(31):[Medline]. [Full Text].
2. Aitken ID, Bogel K, Cracea E, et al. Q fever in Europe: current aspects of aetiology, epidemiology, human infection, diagnosis and therapy. Infection. 1987;15(5):323-7. [Medline].
3. CDC. Q fever outbreak--Germany, 1996. MMWR Morb Mortal Wkly Rep. Jan 17 1997;46(2):29-32. [Medline].
4. CDC. Q Fever: Diagnosis & Laboratory Guidance For Clinicians. CDC. Available at http://emergency.cdc.gov/agent/qfever/clinicians/diagnosis.asp. Accessed September 4, 2008.
5. Cunha BA. The atypical pneumonias: clinical diagnosis and importance. Clin Microbiol Infect. May 2006;12 Suppl 3:12-24.
6. Madariaga MG, Rezai K, Trenholme GM. Q fever: a biological weapon in your backyard. Lancet Infect Dis. Nov 2003;3(11):709-21. [Medline].
7. Mann JS, Douglas JG, Inglis JM. Q fever: person to person transmission within a family. Thorax. Dec 1986;41(12):974-5. [Medline].
8. Marrie TJ. Coxiella burnetii (Q fever). In: Principles and Practice of Infectious Diseases. 4^th ed. Churchill Livingstone; 1995:1727-35.
9. Marrie TJ. Q fever pneumonia. Curr Opin Infect Dis. Apr 2004;17(2):137-42. [Medline].
10. MMWR. Q fever--California, Georgia, Pennsylvania, and Tennessee, 2000-2001. MMWR Morb Mortal Wkly Rep. Oct 18 2002;51(41):924-7. [Medline].
11. Parker NR, Barralet JH, Bell AM. Q fever. Lancet. Feb 25 2006;367(9511):679-88. [Medline].
12. Raoult D, Marrie TJ. Q fever. In: Clinical Infectious Diseases. Oxford University Press; 1995:489-96.
13. Warfare Borden Institute, Walter Reed Army Medical Center. Textbook of Military Medicine Medical Aspects of Chemical and Biological Warfare.

Article Last Updated: Sep 25, 2008