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QTest: A new way to easily sample, store, and ship samples to perform Q fever PCR analysis on bulk tank milk
Michael Treilles1, Pierre Charollais1, Raphaël Guatteo2
1Laboratoire Qualyse, ZAE Montplaisir, 79220 Champdeniers-St. Denis, France.
Insights
A new Q fever diagnostic tool uses milk samples dried on FTA cards, simplifying sample transport and improving detection rates. This method enhances Q fever control strategies for dairy herds.
Area of Science:
- Veterinary Diagnostics
- Microbiology
- Molecular Biology
Background:
- Bulk tank milk (BTM) is a cost-effective sample for detecting Coxiella burnetii (Q fever) in dairy herds via real-time PCR.
- Current BTM PCR methods face challenges with sample stability, refrigeration, and shipping regulations for non-inactivated samples.
Purpose of the Study:
- To develop and validate an innovative diagnostic tool (QTest) for Q fever detection in BTM.
- To assess the stability of Coxiella burnetii DNA in milk samples stored on FTA cards under various conditions.
- To compare the diagnostic accuracy of FTA card-preserved BTM samples with raw BTM samples.
Main Methods:
- Milk samples were applied to Whatman FTA Elute Micro Cards (FTA cards) and air-dried.
- Stability of C. burnetii DNA on FTA cards was tested at room temperature and 37°C for up to 29 days.
- Real-time PCR was performed on both raw BTM and FTA card-preserved BTM samples for comparison.
Main Results:
- C. burnetii DNA remained stable on FTA cards for at least 29 days at room temperature and 37°C.
- Detection rates for Q fever were higher using FTA card-preserved BTM (91.4%) compared to raw BTM (77.6%) in field samples tested 10-14 days after collection.
- The FTA card method demonstrated improved practicality and ease of use for herd-level Q fever diagnosis.
Conclusions:
- FTA card preservation offers a stable and practical method for mailing milk samples for Q fever PCR testing.
- This technique overcomes limitations of raw milk sample transport, facilitating easier herd-level diagnosis and Q fever control.
- The QTest tool supports Q fever management strategies, particularly in regions with limited laboratory infrastructure.
Abstract:
Bulk tank milk (BTM) is an easy, inexpensive, and representative sample for detection of Coxiella burnetii infections (Q fever) in dairy herds using real-time PCR. Bulk tank milk PCR can be performed either for initial herd screening or for monitoring the effectiveness of preventive measures. However, one major limitation under field conditions is the need to deliver BTM samples in adequate condition (quickly, safely, and under refrigeration) to a qualified laboratory. In addition, sending non-inactivated biological samples via normal mail may be prohibited. We developed an innovative, easy, and accurate diagnostic tool (QTest) for Q fever to support veterinarians and farmers in overcoming these constraints. The farmer or veterinarian simply places some drops of BTM on a Whatman FTA Elute Micro Card (FTA card) and lets the card dry before mailing it to the laboratory. In a 2-step study, we tested the hypotheses that (1) BTM samples stored on FTA cards are stable over time and at different temperatures, and (2) PCR results obtained via FTA cards are consistent with those obtained from raw BTM samples. The stability of C. burnetii DNA in milk preserved on an FTA card was maintained for at least 29 d at room temperature or 37°C to mimic field conditions. In our field study, of the original 70 positive BTM samples (when tested on raw BTM just after sampling), 58 samples were positive (on either raw BTM or FTA card) by the time of the direct comparison study (10 to 14 d later). Of these 58 samples, 45 raw BTM samples still tested positive after aging, and 53 FTA card BTM samples tested positive, indicating that detection was higher using FTA cards (91.4%) than raw milk (77.6%). Therefore, with inactivation and shipping advantages, this technique facilitates an easier and more practical approach to diagnosis of Q fever at the herd level and would support Q fever control strategies, especially in countries lacking adequate and close laboratory facilities.
