Treilles Michael, Charollais Pierre, Guatteo Raphaël, Azevedo Carla, Achard Damien, Munoz-Bielsa Juan, Gisbert Philippe
Laboratoire Qualyse, ZAE Montplaisir, 79220 Champdeniers-St. Denis, France.
INRAE, Oniris, BIOEPAR, 44300 Nantes, France.
JDS Commun. 2021 Sep 23;2(6):409-414. doi: 10.3168/jdsc.2021-0144. eCollection 2021 Nov.
Bulk tank milk (BTM) is an easy, inexpensive, and representative sample for detection of 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 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.
使用实时聚合酶链反应（PCR）检测奶牛场感染（Q热）时，大罐奶（BTM）是一种简便、经济且具有代表性的样本。大罐奶PCR可用于牛群的初始筛查或监测预防措施的有效性。然而，在现场条件下，一个主要限制是需要将大罐奶样本在适当条件下（快速、安全且冷藏）送到合格实验室。此外，通过普通邮件寄送未灭活的生物样本可能会被禁止。我们开发了一种创新、简便且准确的Q热诊断工具（QTest），以帮助兽医和农民克服这些限制。农民或兽医只需在Whatman FTA Elute微卡（FTA卡）上滴几滴大罐奶，让卡片干燥后再邮寄到实验室。在一项分两步进行的研究中，我们检验了以下假设：（1）储存在FTA卡上的大罐奶样本在不同时间和温度下是稳定的，（2）通过FTA卡获得的PCR结果与从原始大罐奶样本获得的结果一致。为模拟现场条件，保存在FTA卡上的牛奶中的DNA在室温或37°C下至少保持29天稳定。在我们的现场研究中，最初的70份阳性大罐奶样本（采样后立即对原始大罐奶进行检测时），在直接比较研究时（10至14天后），有58份样本（原始大罐奶或FTA卡上）呈阳性。在这58份样本中，45份原始大罐奶样本老化后仍呈阳性，53份FTA卡大罐奶样本呈阳性，这表明使用FTA卡检测的阳性率（91.4%）高于生奶（77.6%）。因此，由于具有灭活和运输优势，该技术为牛群水平的Q热诊断提供了一种更简便、实用的方法，并将支持Q热控制策略，特别是在缺乏足够和紧密实验室设施的国家。
