Pseudoepidemic of Q fever at an animal research facility

Area of Science:

• Veterinary Medicine
• Infectious Diseases
• Public Health

Background:

• A commercial laboratory reported a high Coxiella burnetii seroprevalence (75%) in individuals exposed to sheep at a research facility.
• This finding suggested a potential outbreak of Q fever, a zoonotic disease.
• Concerns were raised regarding laboratory quality control and accurate diagnostic testing.

Purpose of the Study:

• To investigate the accuracy of the commercial laboratory's Coxiella burnetii testing.
• To determine the true seroprevalence of Coxiella burnetii in the exposed population.
• To identify the source of discrepancy and implement corrective actions.

Main Methods:

• Retrospective analysis of serum samples initially tested by a commercial laboratory.
• Re-testing of samples using an in-house CDC assay and the same commercial test kits at CDC.
• Interviews with individuals to assess exposure history and compatible illness.

Main Results:

• The commercial laboratory's initial results were found to be misinterpreted, leading to an inflated seroprevalence.
• Corrected analysis revealed a true Coxiella burnetii seroprevalence of 27%.
• Only the attending veterinarian was confirmed as a Q fever case, indicating a pseudoepidemic.

Conclusions:

• A lapse in laboratory quality control caused a pseudoepidemic of Q fever.
• Standardization and improved review of laboratory procedures are crucial for accurate diagnostic testing.
• Enhanced public health communication and risk reduction protocols were implemented at the facility.