Q fever

1. Q fever

2. Overview • “Query” fever • First described in Australia • World wide zoonosis • Caused by the bacterium Coxiella burnetii

3. Infectious Agent • Coxiella burnetii • obligate intracellular organism • organism very stable in environment • resistant to drying, chemicals and may disinfectants. • two antigenic phases: phase I and II • phase I (lipopolysaccharide present) - as found in nature, virulent • phase II (partial loss of lipopolysaccharide) - as found after multiple laboratory passages, less infectious

4. Epidemiology • Occurrence • worldwide, endemic in every part of the world except New Zealand. • esp. prevalent in meatworks, dairies and animal farms therefore making Q fever an occupational hazard • Reservoir • cattle, sheep, goats, some wild animals,ticks, domestic cats

5. Clinical Notes • Clinical signs often subclinical or extremely mild • Infection can be acute or chronic • Acute infection • no typical form of acute Q fever, although there are generally 3 major presentations 1) Self-limited flue-like syndrome 2) Pneumonia 3) Hepatitis

6. Clinical Notes cont... • Chronic Q fever • lasts more than 6 months • occurs in approx. 5% of patients infected with C. burnetii • C. burnetii multiplies in macrophages • heart is the most commonly involved organ • of all cases of endocarditis it represents:- • 3% in England and Lyon (France) • 15% in Marseille (France)

7. Clinical Notes cont... • Mode of Transmission • airborne dissemination of organisms in dust and direct contact with infected animals • transplacental transmission congenital infection. • blood transmissions • intradermal inoculation • ticks transmit to domestic animals but not to humans. • sexual transmission suspected. • Incubation Period • Usually 2-3 weeks • Treatment • Tetracycline and rifampin

8. Antibody response • Antibodies to phase 1 • indicates chronic infection • Antibodies to phase 2 • IgM & IgA appear shortly after onset of symptoms & may persist for up to 3 months • IgG appears shortly after IgM & remain for life • indicates acute infection but also persist throughout chronic infection. • phase 2 molecules are highly immunogenic compared to phase 1 • phase 1 molecules are masked in acute infection and therefore not exposed to the host’s immune system

9. Diagnosis • Culture • Complement fixation test (CFT) • Indirect immunofluorescence assay (IFA) • ELISA

10. Culture • Hazardous • Not routinely used • Requires specially equipped laboratory

11. CFT • Usually phase II antigen • CF antibodies may not be detectable early in acute infection • CF antibodies may persist for months/years • Usually requires paired sera

12. IFA • Accepted method of diagnosis (“Gold Standard”) • More sensitive than CFT • Can measure individual antibody classes to different phase and can therefore be used to distinguish between acute & chronic infection • Ideal for confirmation and small volume testing

13. ELISA • More sensitive than IFA (IgG studies) • Very specific • Suitable for large scale screening • Diagnosis can be based on single serum specimen when IgM ELISA used • Can measure responses to different classes of antibody

14. Panbio Q fever ELISAs C. burnetii (Q fever) IgG ELISA Cat # E-QFB01G C. burnetii (Q fever) IgM ELISA Cat # E-QFB01M • Phase II antigen • Ideal for laboratory use • 1hr 10min assay time • IgG and IgM kits available • Proven performance 1,2,3 • IgM ELISA sensitivity 99%, specificity 88%1 • IgG ELISA sensitivity71%, specificity 96% 2; sensitivity 98.4%, specificity 95.7% (compared to IFA using cutoff titre of 1/160)3

15. Panbio Q fever Dip-S-Tick C. burnetii Total Ig Dip-S-Tick kit Cat# D-QFB03T • Has dots for both Phase I and Phase II antigens. • Three dots are for Phase II (acute infection) determination and one is for Phase I (chronic infection) determination. • Built in control well indicates test has worked correctly • Convenient for small-volume testing • No special equipment other than a 50°C waterbath required • Semi-quantitative

16. Panbio Q fever Dip-S-Tick: configuration

17. Panbio Q fever IFA C. burnetii (Q fever) IFA Slides Cat#I-QFB01X • Contain both Phase I and Phase II purified organisms as well as a normal yolk sac (NYS) control. • All three are represented on each well of the slides as distinct microdots (figure 1). • Dilutions of the patient's serum are placed in wells on the slide, permitting the antibody to bind specifically to the organisms. Bound antibodies are tagged with a fluorescein labeled anti-human conjugate and observed using a fluorescence microscope. In this format, organisms are readily identified as small coccobacilli. Fluorescent coxiellae are bright yellow against a dull red background (counterstain).

18. Panbio Q fever IFA Figure 1 Dot configuration in slide well as seen through the microscope

19. Promotional Resources • Clinical Sheet • Publications • General • Panbio Q fever ELISAs • Newsletter articles

20. References • Field P. et al. (2000) J. Clin. Microbiol. 34(4):1645-47. • Field P. et al (2002) J. Clin. Microbiol. 40(9):3526-29. • D’Harcourt et al. (1996) Eur. J. Clin. Micro. Infect. Dis. 15:749-52.