Q fever (etiologic agent: Coxiella burnetii)

Test code: B0066 - Ultrasensitive detection of Coxiella burnetii by real time PCR

Q fever is a zoonotic disease caused by Coxiella burnetii, an obligate intracellular bacterium which lives only in nucleated cells and is present ubiquitously in the environment.

Cattle, sheep, and goats are the primary reservoirs of C. burnetii. However, many other animals can be infected including other species of livestock and pets. Infection of these animals does not usually result in clinical symptoms, and even in goats and sheep abortion is the major clinical symptom reported.

Infected asymptomatic domestic animals can spread the disease to humans.  Infected animals can excrete the bacteria in milk, urine, and feces. Most importantly, the organisms are shed in high numbers in amniotic fluid and placenta during birthing. 

C. burnetii is highly resistant to heat, drying, and many common disinfectants. It can survive for long periods in the environment, and be transmitted to humans by inhalation of aerosols and dust at farms and other animal facilities. 

Humans are very susceptible to the disease and inhalation of only very few organisms is sufficient to cause infection. Ingestion of contaminated milk or milk products can transmit the disease but is not common.  Transmission to humans can also occur through tick bites.  However, direct human to human transmission is very rare. 

Culture detection of the bacteria is difficult and is not available in most laboratories. Serological detection of the bacteria is unreliable. For example, serum antibodies are detectable about 2 weeks after the initial infection of sheep. The antibody concentrations reach a maximum at 30 to 60 days, then rapidly decline and phase into the seasonal antibody cycle of the rest of the flock in relation to the lambing season (McCaul et al, 1981). Therefore, if the infected sheep is tested by serology during the low point of the cycle, when antibody concentration is below the detectable level, it will be misleading to claim a seronegative flock basing on the testing result.

Molecular detection by PCR is unaffected by changes in the infection cycle, and enables rapid, sensitive and specific detection of C. burnetii in a sample (Panning et al., 2008).

Utilities:

• Confirm the disease causing agent
• Identify Q fever carriers
• Ensure that animal facilities and populations are free of Q fever
• Early prevention of spread of Q fever among animals
• Minimize human exposure to Q fever
• Safety monitoring of biological products that derive from animals

References:
McCaul, T.F., Hakstadt, T. and Williams, J.C. (1981) Ultrastructural and biological aspects of Coxiella burnetii under physical disruptions. In: Burgdorfer W, Anacker RL, eds. Rickettsiae and rickettsial diseases. New York: Harcourt Brace Jovanovich, 1981.

Panning, M., Kilwinski, J., Greiner-Fischer, S., Peters, M., Kramme, S., Frangoulidis, D., Meyer, H., Henning, K. and Drosten, C. (2008) High throughput detection of Coxiella burnetii by real-time PCR with internal control system and automated DNA preparation. BMC Microbiol. 8:77.

Specimen requirements: Whole blood in EDTA (purple top) or ACD (yellow top) tube, or rectal swab or genital swab, or 0.5 ml feces, milk, urine, amniotic fluid or aborted tissue.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR

Normal range: Nondetected