Abstract
BackgroundQ fever, a zoonosis caused by Coxiella burnetii, has adverse effects on public health. Ticks are vectors of C. burnetii and they contribute to the transmission of the pathogen. A tool for rapid, sensitive, and accurate detection of C. burnetii from ticks is important for the prevention of Q fever.MethodsUltra-rapid real-time PCR (UR-qPCR) as a chip-based real-time PCR system was developed for the detection of C. burnetii from ticks. The UR-qPCR system was established and evaluated for the rapidity, sensitivity, and specificity of C. burnetii detection.ResultsC. burnetii was detected using UR-qPCR from 5644 larval, nymphal, and adult ticks from 408 pools collected from livestock and epidemiologically linked environments in two provinces, Gangwon and Jeju, in Korea. Ticks from three species were identified; Haemaphysalis longicornis accounted for the highest number, present in 333 of 408 pools (81.62%), followed by Haemaphysalis flava in 62 pools (15.19%) and Ixodes nipponensis in 13 pools (3.19%). The rapidity and sensitivity of PCR detection was demonstrated with the sufficient amplification and detection of approximately 56 copies of C. burnetii DNA with only 20 min of PCR amplification. The kappa value for the diagnostic agreement between UR-qPCR and stationary qPCR was in perfect agreement (κ = 1). PCR detection and sequencing indicated that C. burnetii was present in 5 of the 408 pools (1.23%), in which four pools contained H. longicornis and one pool contained H. flava. The infection rates of C. burnetii in the tick pools collected from Gangwon and Jeju Provinces were 1.70% and 0.58%, respectively. Phylogenetic analysis indicated a close relationship between the detected C. burnetii and those originating from goats, humans, and ticks in different countries, such as the USA, France, Germany, and Serbia.ConclusionsThe methods described in this study could be important for the prevention and control of Q fever in the two provinces. The UR-qPCR, with its features of mobility, sensitivity, and rapidity, is helpful for constructing early alert systems in the field for C. burnetii in ticks and could help alleviate the transmission of and economic damage due to Q fever.Graphical
Highlights
Q fever, a zoonosis caused by Coxiella burnetii, has adverse effects on public health
The linear regression representing the relationship between initial DNA copy number and cycle threshold (Ct) from triplicate Polymerase chain reaction (PCR) reactions was determined by y = −3.1797x + 45.079; R2 = 0.9977, where y and x are the Ct value and log10 DNA copy number, respectively (Fig. 1b)
Rickettsiella spp. [37, 38]; we showed that the Coxiella-like bacteria (CLB) in ticks does not interfere with the accuracy of C. burnetii detection using sequencing, and the comparison of the C. burnetii-specific primers used in this study to genomes of Rickettsiella spp. showed that there was no amplification of the primers on Rickettsiella genome with the amplicon size that could interfere with the accurate detection of C. burntetii (Additional file 1: Fig. S1)
Summary
Q fever, a zoonosis caused by Coxiella burnetii, has adverse effects on public health. Ticks are vectors of C. burnetii and they contribute to the transmission of the pathogen. A tool for rapid, sensitive, and accurate detection of C. burnetii from ticks is important for the prevention of Q fever. C. burnetii infects a variety of vertebrates and is a key threat to veterinary and human health worldwide [2, 3]. The transmission to humans mainly occurs through inhalation of bacteria from contaminated faeces, close contact with. A method for sensitive and accurate detection of C. burnetii from ticks is important to prevent infection of humans directly from ticks or indirectly via animals that were hosts of infected ticks [13,14,15]
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