The project is financially funded by Thailand Research Fund (TRF) grant number RDG6050078 and the Center for Advanced Studies for Agriculture and Food, Institute for Advanced Studies, Kasetsart University, Bangkok, Thailand under the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission, Ministry of Education, Thailand. The research is supported in part by the Graduate Program Scholarship from the Graduate School, Kasetsart University. The authors would like to thank Dr. Kwanrawee Sirikanchana for the narrative speaking of the video and Piyawatchara Sikarin for editing the video.

This experiment, which involved the use of animal tissue, was approved by the Institutional Animal Care and Use Committee of Kasetsart University, Bangkok, Thailand (protocol number ACKU61-VET-009).
1. Tissue collection
<ol>
	<li>Euthanize tilapia fish using an overdose of clove oil (i.e., more than 3 mL/L). Tricaine methanesulfonate can be used as an alternative to clove oil.</li>
	<li>Use sterile mayo scissors and forceps to cut open the abdomen of the postmortem tilapia and excise approximately 30&#8211;50 mg of liver tissue, or using a microscope cover glass, collect 100&#160;&#181;L of mucus by scraping the fish skin layer longitudinally (from anterior to posterior) into a 1.5 mL microcentrifuge tube.</li>
	<li>Proceed to the RNA extraction step immediately or keep the collected sample at &#8722;80 &#176;C until the experiment. As intact RNA is more sensitive than DNA, use RNase-free materials and reagents during the RNA extraction.</li>
</ol>
2. RNA extraction
<ol>
	<li>To extract the RNA from the liver tissue, add 30&#8211;50 mg of the tilapia tissue to a 1.5 mL microcentrifuge tube containing 600&#8211;1,000 &#181;L of guanidinium-acid-phenol extraction reagent (Table of Materials), and pulverize the sample until homogenous using a hand-held tissue homogenizer. The tissue samples require approximately 10% of the guanidinium-acid-phenol extraction reagent. For the mucus samples, use only 300 &#181;L of the guanidinium-acid-phenol extraction reagent (3:1). 
	CAUTION: The guanidinium-acid-phenol extraction reagent is toxic; hence, handling must be undertaken with care. Protective equipment, such as safety glasses, a laboratory gown, and safety gloves, must be worn.</li>
	<li>Centrifuge the homogenized sample at 10,000 x g for 30 s at room temperature, and transfer the supernatant into a new sterile 1.5 mL microcentrifuge tube.</li>
	<li>Add an equal volume of 95% ethanol to the tube and mix well.</li>
	<li>Transfer the solution into a spin column (Table of Materials) placed in a collection tube and centrifuge at 10,000 x g for 30 s at room temperature. Discard the flow-through, and transfer the spin column to a new collection tube.</li>
	<li>Add 400 &#181;L of RNA Pre-Wash reagent (Table of Materials) to the column and centrifuge at 10,000 x g for 30 s at room temperature before discarding the flow-through. Repeat this step one more time. 
	NOTE: To prepare the RNA Pre-Wash, add 10 mL of 95% ethanol to 40 mL of RNA Pre-Wash concentrate.</li>
	<li>Add 700 &#181;L of RNA Wash Buffer (Table of Materials) to the column and centrifuge at 10,000 x g for 2 min at room temperature. Transfer the column to a sterile 1.5 mL microcentrifuge tube. 
	NOTE: To prepare RNA Wash Buffer, add 52 mL of 95% ethanol to 12 mL of RNA Wash Buffer concentrate.</li>
	<li>Elute the RNA sample captured in the spin column matrix with 100 &#181;L of nuclease-free water and centrifuge at 10,000 x g for 30 s at room temperature.</li>
	<li>Measure the concentration of the extracted RNA using a microvolume spectrophotometer and dilute the RNA to a desired concentration using nuclease-free water. 
	NOTE: The qualified absorbance value of OD260/OD280 ranges from 1.6 to 1.9, indicating the acceptable RNA purity for the RT-LAMP assay.</li>
	<li>Proceed to the next step immediately, or keep the sample at &#8722;80 &#176;C until use.</li>
</ol>
3. Primer design
<ol>
	<li>Use Primer Explorer version 4 to design the specific primers for the RT-LAMP. Go to the website, https://primerexplorer.jp/e/, and click on the PrimerExplorer V4 button.</li>
	<li>Select the file containing the sequences of segment 3 of TiLV in FASTA format and then click the Primer Design button. 
	NOTE: Retrieve the sequences in FASTA format from GenBank accession number KX631923, which represents tilapia lake virus TV1 segment 31.</li>
	<li>To design the primers, input the following basic parameters: 
	-&#160; &#160;A GC content of 40%&#8211;60% 
	-&#160; &#160;An amplicon of &#8805;280 base pairs (bp) 
	-&#160; &#160;A similar melting temperature (Tm) among primers with a maximum difference of 5 &#176;C 
	NOTE: The primers must not complement each other
	<ol>
		<li>Avoid sequence regions prone to forming secondary structures.</li>
		<li>Select the dimer primer analysis with a minimum of &#8722;3.5 for an optimal design for the largest &#916;G, and select the ends of the primers with a maximum of &#8722;4 for an optimal design for the smaller &#916;G.</li>
	</ol>
	</li>
	<li>Click the Generate button. 
	NOTE: After the software finishes processing the input data, the primer results will be shown (Figure 1).</li>
</ol>
4. RT-LAMP assay
<ol>
	<li>Prepare an RT-LAMP master mix containing 2.5 &#181;L of 1x SD II reaction buffer, 3 &#181;L of 6&#160;mM MgSO4, 1.4 &#181;L of 1.4 mM dNTP set, 4 &#181;L of 0.8 M betaine, 1.3 &#181;L of 0.052 mM calcein mixture, 1 &#181;L of 1.6 &#181;M TiLV-F3 primer, 1 &#181;L of 1.6 &#181;M TiLV-B3 primer, 1 &#181;L of 0.2 &#181;M TiLV-BIP primer, 1 &#181;L of 0.2 &#181;M TiLV-FIP primer, 1 &#181;L of 0.3 U Bst DNA polymerase, 1 &#181;L of 0.1 U AMV reverse transcriptase, and 3.8 &#181;L of nuclease-free water per reaction. 
	NOTE: Prepare excess master mix comprising at least 10% of the total reaction volume.</li>
	<li>Dispense 22 &#181;L of the RT-LAMP master mix into a sterile 1.5 microcentrifuge tube.</li>
	<li>Add 3 &#181;L of the extracted RNA to the reaction tube, and mix the sample by vortexing. For the negative control, use distilled water instead of RNA materials.</li>
	<li>Incubate the reaction at 65 &#176;C for 60 min, followed by 80 &#176;C for 10 min to terminate the reaction.</li>
	<li>After incubation, visually observe the colorimetric changes with the naked eye. A positive result will appear as a fluorescent green color.</li>
</ol>
5. Agarose gel electrophoresis
<ol>
	<li>Prepare a 1.5% w/v agarose gel by suspending&#160;0.6 g of agarose powder in 40 mL of 1x TAE buffer. Melt the mixture by heating it in a microwave for 3&#8211;5 min until the agarose is completely dissolved, and swirl to mix.</li>
	<li>Allow the agarose to cool down until the temperature reaches 65 &#176;C. Pour 40 mL of the agarose solution onto a gel tray and add a comb to the gel mold.</li>
	<li>Allow the agarose gel to set at room temperature for 20&#8211;30 min until it has completely solidified. Then remove the comb and place the gel in the gel tank.</li>
	<li>Add a running buffer to cover the surface of the gel in the gel tank.</li>
	<li>Add 10 &#181;L of the RT-LAMP sample and 2 &#181;L of 6x gel loading buffer to each well. Add 5 &#181;L of a 1 kb DNA ladder to the reference lane.</li>
	<li>Plug in the lid attached to the cathode and the anode connected to a power supply. Turn on the power supply, set it to a constant 100 V, and run for 40 min.</li>
	<li>After completing the gel separation, remove the gel from the gel tray. Then stain the drained gel using ethidium bromide (EtBr) at a concentration of 10 mg/mL&#160;for 7 min and restain it in distilled water for 5 min. 
	CAUTION: EtBr is toxic and considered a carcinogen; therefore, be careful when using this agent.</li>
	<li>Expose the gel to UV light using a gel documentation system where bands appear, and take a picture of the gel.</li>
</ol>
6. Complementary DNA (cDNA) synthesis
<ol>
	<li>Prepare a cDNA synthesis master mix containing 2 &#181;L of 5x RT buffer, 0.5 &#181;L of primer mix, 0.5 &#181;L of RT enzyme, and 2 &#181;L of nuclease-free water per reaction. 
	NOTE: Prepare excess master mix comprising 1x the reaction due to potential loss during pipetting.</li>
	<li>Dispense 5 &#181;L of the master mix into a sterile 1.5 mL microcentrifuge tube.</li>
	<li>Add 100 ng of the diluted extracted RNA (obtained from step 2.8) to the reaction tube, mix and spin down to move all the mixture to the bottom of the vessel.</li>
	<li>Incubate the reactions at 42 &#176;C for 60 min, followed by 98 &#176;C for 5 min in a PCR machine. Store the cDNA at &#8722;20 &#176;C until use.</li>
</ol>
7. RT-qPCR
<ol>
	<li>Prepare a TiLV qPCR master mix containing 0.3 &#181;L of 10 &#181;M reverse primer, 0.3 &#181;L of 10 &#181;M&#160;forward primer, 5 &#181;L of 2x SYBR Green DNA polymerase, and 0.4 &#181;L of nuclease-free water per reaction. Use the following primers and controls: 
	Forward primer (TiLV-112F):&#160; 5&#39;-CTGAGCTAAAGAGGCAATATGGATT-3&#39; 
	Reverse primer (TiLV-112R):&#160; 5&#39;-CGTGCGTACTCGTTCAGTATAAGTTCT-3&#39;</li>
	<li>Dispense 6 &#181;L of the TiLV qPCR master mix into each well of the qPCR strip compatible with the real-time thermal cycler used.</li>
	<li>Add 4 &#181;L of the cDNA template, negative control (nuclease-free water), positive control (10 pg/&#181;L), and pTiLV (plasmid)10 or serially diluted TiLV plasmid to the well, and mix each sample by flicking. Conduct each sample in triplicate.</li>
	<li>Place the qPCR reactions into the programmed real-time thermal cycler. Set the qPCR program to perform the incubation at 95 &#176;C for 3 min, followed by 40 cycles of 95 &#176;C for 10 s and 60 &#176;C for 30 s before the melting curve step in which the temperature needs to increase from 65 &#176;C to 95 &#176;C at 0.5 &#176;C/5 s increments.</li>
	<li>Conduct the data analysis by evaluating the amplification and melting curves, and then compute the number of TiLV copies using the standard curve obtained from the data using the serially diluted plasmids.</li>
</ol>

<ol>
	<li>Surachetpong, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Outbreaks+of+Tilapia+Lake+Virus+Infection,+Thailand,+2015-2016.">Outbreaks of Tilapia Lake Virus Infection, Thailand, 2015-2016.</a> Emerging Infectious Diseases. 23 (6), 1031-1033 (2017).</li><li>Eyngor, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+a+novel+RNA+virus+lethal+to+tilapia.">Identification of a novel RNA virus lethal to tilapia.</a> Journal of Clinical Microbiology. 52 (12), 4137-4146 (2014).</li><li>Adams, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+to+taxonomy+and+the+International+Code+of+Virus+Classification+and+Nomenclature+ratified+by+the+International+Committee+on+Taxonomy+of+Viruses+(2017).">Changes to taxonomy and the International Code of Virus Classification and Nomenclature ratified by the International Committee on Taxonomy of Viruses (2017).</a> Archives of Virology. 162 (8), 2505-2538 (2017).</li><li>Bacharach, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+a+Novel+Orthomyxo-like+Virus+Causing+Mass+Die-Offs+of+Tilapia.">Characterization of a Novel Orthomyxo-like Virus Causing Mass Die-Offs of Tilapia.</a> MBio. 7 (2), 00431 (2016).</li><li>Jaemwimol, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Susceptibility+of+important+warm+water+fish+species+to+tilapia+lake+virus+(TiLV)+infection.">Susceptibility of important warm water fish species to tilapia lake virus (TiLV) infection.</a> Aquaculture. 497, 462-468 (2018).</li><li>Giews, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Global+Information+and+Early+Warning+System+On+Food+And+Agriculture.">Global Information and Early Warning System On Food And Agriculture.</a> Food and Agriculture Organization of the United Nations. , (2017).</li><li>Al-Hussinee, L., Subramaniam, K., Ahasan, M. S., Keleher, B., Waltzek, T. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Complete+Genome+Sequence+of+a+Tilapia+Lake+Virus+Isolate+Obtained+from+Nile+Tilapia+(Oreochromis+niloticus).">Complete Genome Sequence of a Tilapia Lake Virus Isolate Obtained from Nile Tilapia (Oreochromis niloticus).</a> Genome Announcements. 6 (26), (2018).</li><li>Thammatorn, W., Rawiwan, P., Surachetpong, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Minimal+risk+of+tilapia+lake+virus+transmission+via+frozen+tilapia+fillets.">Minimal risk of tilapia lake virus transmission via frozen tilapia fillets.</a> Journal of Fish Diseases. 42 (1), 3-9 (2019).</li><li>Fathi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+Tilapia+Lake+Virus+in+Egypt+in+Nile+tilapia+affected+by+'summer+mortality'+syndrome.">Identification of Tilapia Lake Virus in Egypt in Nile tilapia affected by 'summer mortality' syndrome.</a> Aquaculture. 473, 430-432 (2017).</li><li>Tattiyapong, P., Sirikanchana, K., Surachetpong, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+validation+of+a+reverse+transcription+quantitative+polymerase+chain+reaction+for+tilapia+lake+virus+detection+in+clinical+samples+and+experimentally+challenged+fish.">Development and validation of a reverse transcription quantitative polymerase chain reaction for tilapia lake virus detection in clinical samples and experimentally challenged fish.</a> Journal of Fish Diseases. 41 (2), 255-261 (2018).</li><li>Waiyamitra, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+TaqMan+RT-qPCR+assay+for+tilapia+lake+virus+(TiLV)+detection+in+tilapia.">A TaqMan RT-qPCR assay for tilapia lake virus (TiLV) detection in tilapia.</a> Aquaculture. 497, 184-188 (2018).</li><li>Kembou Tsofack, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+Tilapia+Lake+Virus+in+Clinical+Samples+by+Culturing+and+Nested+Reverse+Transcription-PCR.">Detection of Tilapia Lake Virus in Clinical Samples by Culturing and Nested Reverse Transcription-PCR.</a> Journal of Clinical Microbiology. 55 (3), 759-767 (2017).</li><li>Dong, H. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emergence+of+tilapia+lake+virus+in+Thailand+and+an+alternative+semi-nested+RT-PCR+for+detection.">Emergence of tilapia lake virus in Thailand and an alternative semi-nested RT-PCR for detection.</a> Aquaculture. 476, 111-118 (2017).</li><li>Notomi, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loop-mediated+isothermal+amplification+of+DNA.">Loop-mediated isothermal amplification of DNA.</a> Nucleic Acids Research. 28 (12), 63 (2000).</li><li>Mori, Y., Notomi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loop-mediated+isothermal+amplification+(LAMP):+a+rapid,+accurate,+and+cost-effective+diagnostic+method+for+infectious+diseases.">Loop-mediated isothermal amplification (LAMP): a rapid, accurate, and cost-effective diagnostic method for infectious diseases.</a> Journal of Infection and Chemotherapy. 15 (2), 62-69 (2009).</li><li>Mori, Y., Nagamine, K., Tomita, N., Notomi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+loop-mediated+isothermal+amplification+reaction+by+turbidity+derived+from+magnesium+pyrophosphate+formation.">Detection of loop-mediated isothermal amplification reaction by turbidity derived from magnesium pyrophosphate formation.</a> Biochemical and Biophysical Research Communications. 289 (1), 150-154 (2001).</li><li>Caipang, C. M., Haraguchi, I., Ohira, T., Hirono, I., Aoki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+detection+of+a+fish+iridovirus+using+loop-mediated+isothermal+amplification+(LAMP).">Rapid detection of a fish iridovirus using loop-mediated isothermal amplification (LAMP).</a> Journal of Virological Methods. 121 (2), 155-161 (2004).</li><li>Soliman, H., El-Matbouli, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+inexpensive+and+rapid+diagnostic+method+of+Koi+Herpesvirus+(KHV)+infection+by+loop-mediated+isothermal+amplification.">An inexpensive and rapid diagnostic method of Koi Herpesvirus (KHV) infection by loop-mediated isothermal amplification.</a> Virology Journal. 2, 83 (2005).</li><li>Gunimaladevi, I., Kono, T., Venugopal, M. N., Sakai, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+koi+herpesvirus+in+common+carp,+Cyprinus+carpio+L.,+by+loop-mediated+isothermal+amplification.">Detection of koi herpesvirus in common carp, Cyprinus carpio L., by loop-mediated isothermal amplification.</a> Journal of Fish Diseases. 27 (10), 583-589 (2004).</li><li>Gunimaladevi, I., Kono, T., Lapatra, S. E., Sakai, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+loop+mediated+isothermal+amplification+(LAMP)+method+for+detection+of+infectious+hematopoietic+necrosis+virus+(IHNV)+in+rainbow+trout+(Oncorhynchus+mykiss).">A loop mediated isothermal amplification (LAMP) method for detection of infectious hematopoietic necrosis virus (IHNV) in rainbow trout (Oncorhynchus mykiss).</a> Archives of Virology. 150 (5), 899-909 (2005).</li><li>Kono, T., Savan, R., Sakai, M., Itami, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+white+spot+syndrome+virus+in+shrimp+by+loop-mediated+isothermal+amplification.">Detection of white spot syndrome virus in shrimp by loop-mediated isothermal amplification.</a> Journal of Virological Methods. 115 (1), 59-65 (2004).</li><li>Soliman, H., El-Matbouli, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reverse+transcription+loop-mediated+isothermal+amplification+(RT-LAMP)+for+rapid+detection+of+viral+hemorrhagic+septicaemia+virus+(VHS).">Reverse transcription loop-mediated isothermal amplification (RT-LAMP) for rapid detection of viral hemorrhagic septicaemia virus (VHS).</a> Veterinary Microbiology. 114 (3-4), 205-213 (2006).</li><li>Yeh, H. Y., Shoemaker, C. A., Klesius, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+a+loop-mediated+isothermal+amplification+method+for+rapid+detection+of+channel+catfish+Ictalurus+punctatus+important+bacterial+pathogen+Edwardsiella+ictaluri.">Evaluation of a loop-mediated isothermal amplification method for rapid detection of channel catfish Ictalurus punctatus important bacterial pathogen Edwardsiella ictaluri.</a> Journal of Microbiological Methods. 63 (1), 36-44 (2005).</li><li>Yeh, H. Y., Shoemaker, C. A., Klesius, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensitive+and+rapid+detection+of+Flavobacterium+columnare+in+channel+catfish+Ictalurus+punctatus+by+a+loop-mediated+isothermal+amplification+method.">Sensitive and rapid detection of Flavobacterium columnare in channel catfish Ictalurus punctatus by a loop-mediated isothermal amplification method.</a> Journal of Applied Microbiology. 100 (5), 919-925 (2006).</li><li>Sun, Z. F., Hu, C. Q., Ren, C. H., Shen, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensitive+and+rapid+detection+of+infectious+hypodermal+and+hematopoietic+necrosis+virus+(IHHNV)+in+shrimps+by+loop-mediated+isothermal+amplification.">Sensitive and rapid detection of infectious hypodermal and hematopoietic necrosis virus (IHHNV) in shrimps by loop-mediated isothermal amplification.</a> Journal of Virological Methods. 131 (1), 41-46 (2006).</li><li>Shivappa, R. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+spring+viraemia+of+carp+virus+(SVCV)+by+loop-mediated+isothermal+amplification+(LAMP)+in+koi+carp,+Cyprinus+carpio+L.">Detection of spring viraemia of carp virus (SVCV) by loop-mediated isothermal amplification (LAMP) in koi carp, Cyprinus carpio L.</a> Journal of Fish Diseases. 31 (4), 249-258 (2004).</li><li>Wei, X. N., Zheng, Z. J., Zhang, L. H., Qu, F., Huang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensitive+and+rapid+detection+of+Aeromonas+caviae+in+stool+samples+by+loop-mediated+isothermal+amplification.">Sensitive and rapid detection of Aeromonas caviae in stool samples by loop-mediated isothermal amplification.</a> Diagnostic Microbiology and Infectious Disease. 60 (1), 113-116 (2008).</li><li>Chinabut, S., Puttinaowarat, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+choice+of+disease+control+strategies+to+secure+international+market+access+for+aquaculture+products.">The choice of disease control strategies to secure international market access for aquaculture products.</a> Developmental Biology. 121, 255-261 (2005).</li><li>Soto, E., Yun, S., Surachetpong, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Susceptibility+of+Tilapia+Lake+Virus+to+buffered+Povidone-iodine+complex+and+chlorine.">Susceptibility of Tilapia Lake Virus to buffered Povidone-iodine complex and chlorine.</a> Aquaculture. 512, 734342 (2019).</li><li>Jaemwimol, P., Sirikanchana, K., Tattiyapong, P., Mongkolsuk, S., Surachetpong, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Virucidal+effects+of+common+disinfectants+against+tilapia+lake+virus.">Virucidal effects of common disinfectants against tilapia lake virus.</a> Journal of Fish Diseases. 42 (10), 1383-1389 (2019).</li><li>Jansen, M. D., Dong, H. T., Mohan, C. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tilapia+lake+virus:+a+threat+to+the+global+tilapia+industry.">Tilapia lake virus: a threat to the global tilapia industry.</a> Reviews in Aquaculture. 11 (3), 725-739 (2019).</li><li>Yin, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+simple+and+rapid+reverse+transcription-loopmediated+isothermal+amplification+(RT-LAMP)+assay+for+sensitive+detection+of+tilapia+lake+virus.">Development of a simple and rapid reverse transcription-loopmediated isothermal amplification (RT-LAMP) assay for sensitive detection of tilapia lake virus.</a> Journal of Fish Diseases. 42 (6), 817-824 (2019).</li><li>Savan, R., Kono, T., Itami, T., Sakai, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loop-mediated+isothermal+amplification:+an+emerging+technology+for+detection+of+fish+and+shellfish+pathogens.">Loop-mediated isothermal amplification: an emerging technology for detection of fish and shellfish pathogens.</a> Journal of Fish Diseases. 28 (10), 573-581 (2005).</li><li>Phusantisampan, T., Tattiyapong, P., Mutrakulcharoen, P., Sriariyanun, M., Surachetpong, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+detection+of+tilapia+lake+virus+using+a+one-step+reverse+transcription+loop-mediated+isothermal+amplification+assay.">Rapid detection of tilapia lake virus using a one-step reverse transcription loop-mediated isothermal amplification assay.</a> Aquaculture. 507, 35-39 (2019).</li><li>Liamnimitr, P., Thammatorn, W., U-thoomporn, S., Tattiyapong, P., Surachetpong, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-lethal+sampling+for+Tilapia+Lake+Virus+detection+by+RT-qPCR+and+cell+culture.">Non-lethal sampling for Tilapia Lake Virus detection by RT-qPCR and cell culture.</a> Aquaculture. 486, 75-80 (2018).</li><li>Yin, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+simple+and+rapid+reverse+transcription-loopmediated+isothermal+amplification+(RT-LAMP)+assay+for+sensitive+detection+of+tilapia+lake+virus.">Development of a simple and rapid reverse transcription-loopmediated isothermal amplification (RT-LAMP) assay for sensitive detection of tilapia lake virus.</a> Journal of Fish Diseases. 42 (6), 817-824 (2019).</li><li>Khan, R. S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+detection+of+infectious+bursal+disease+by+loop-mediated+isothermal+amplification+for+field+analysis.">Rapid detection of infectious bursal disease by loop-mediated isothermal amplification for field analysis.</a> Iranian Journal of Veterinary Research. 19 (2), 101-107 (2018).</li><li>Nagamine, K., Hase, T., Notomi, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accelerated+reaction+by+loop-mediated+isothermal+amplification+using+loop+primers.">Accelerated reaction by loop-mediated isothermal amplification using loop primers.</a> Molecular and Cellular Probes. 16 (3), 223-229 (2002).</li><li>Debode, F., Marien, A., Janssen, E., Bragard, C., Berben, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+amplicon+length+on+real-time+PCR+results.">The influence of amplicon length on real-time PCR results.</a> Biotechnology, Agronomy, Society and Environment. 21 (1), 3-11 (2017).</li></ol>

The authors have nothing to disclose.

The aquaculture industry is continuously threatened by viral infections that cause substantial economic losses9,23,28. For instance, the emerging TiLV poses a major threat to tilapia-producing countries in many parts of the world1,6,9. Until now, there have been no specific therapeutics available to prevent TiLVD. While the development ...

Tilapia lake virus disease (TiLVD) is a viral disease in tilapia (Oreochromis spp.) that reportedly causes tilapia deaths in many regions of the world, including Asia1,2, Africa, and America. The disease was first recognized during the mass mortality of tilapia in 2009 in Israel, where the number of wild tilapia in Lake Kinneret plummeted dramatically from 257 to 8 tons per year2. The disease is caused by the tilapia lake virus (TiLV), which has been assigned to the family Amnoonviridae as a new genus Tilapinevirus and a new species Tilapia tilapinevirus3. Genetic characterization of TiLV showed that the virus is a novel enveloped, negative-sense, single-stranded RNA virus that has 10 segments encoding 10 proteins1,2,4. Various species of tilapia in the genus Sarotherodon, Oreochromis, and Tilapine and other warm water fish (e.g., giant gourami (Osphronemus goramy)) have been shown to be susceptible to TiLV2,5. Currently, this virus continues to spread globally, possibly through the movement of infected live fish6,7, while the risk of viral transmission via frozen tilapia or its product is limited8. Substantial mortality due to TiLV infection has the potential to have a significantly detrimental economic impact on the tilapia industry. For example, the economic impact of summer mortality syndrome in Egypt associated with TiLV infection was calculated to be US$100 million9. Accordingly, it is important to develop a rapid and proper diagnostic method to facilitate the control of this disease in fish farms.
Until now, the diagnosis of TiLVD has been based on molecular assays, viral isolation, and histopathology. Different PCR protocols and primers have been developed for TiLV diagnosis10,11. For instance, a SYBR green-based reverse transcription quantitative PCR (RT-qPCR) method with the sensitivity to detect as few as two copies/&#181;L of the virus has been developed and validated for TiLV detection10. Other PCR methods for TiLV detection include TaqMan quantitative PCR11, RT-PCR2, nested RT-PCR12, and semi-nested RT-PCR13. However, these methods require sophisticated laboratory equipment and relatively extended periods of time to yield results due to the complexity of the reactions, which makes them unsuitable for field application.
The loop-mediated isothermal amplification (LAMP) assay is a rapid, simple, and practical for-field application14,15. The technique employs the principle of a strand displacement reaction, while the amplification reaction runs under isothermal conditions without a sophisticated and expensive thermal cycler14,15. Consequently, amplified LAMP products or RT-LAMP products are analyzed in ladder-like bands using agarose gel electrophoresis with a fluorescent stain for either the safe visualization of DNA or RNA14 or observation with the naked eye for the presence of turbidity or a white precipitate16,17,18. For these reasons, this technique has been used for the on-site detection of different fish pathogens17,18,19,20,21,22,23,24,25,26,27. The purpose of this study was to establish a rapid, sensitive, and accurate RT-LAMP assay for TiLV detection. The RT-LAMP assay offers screening for TiLV in fish samples within 30 min. The technique may be applied for the diagnosis and surveillance of TiLVD.

<table border="0" cellpadding="0" cellspacing="0" style="width:961px;" width="961">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Tissue collection:</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td style="width:295px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Clove oil</td>
			<td style="width:224px;">Better Pharma</td>
			<td style="width:188px;">N/A</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">Tricaine methanesulfonate</td>
			<td style="width:224px;">Sigma-Aldrich</td>
			<td style="width:188px;">E10521</td>
			<td>An alternative option to clove oil</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">RNA extraction:</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Acid guanidinium-phenol based reagent (TRIzol reagent)</td>
			<td style="width:224px;">ThermoFisher Scientific Corp.</td>
			<td style="width:188px;">15596026</td>
			<td style="width:295px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Acid guanidinium-phenol based reagent (GENEzol reagent)</td>
			<td style="width:224px;">Geneaid</td>
			<td style="width:188px;">GZR100</td>
			<td style="width:295px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Direct-zol RNA Kit:</td>
			<td style="width:224px;">Zymo Research</td>
			<td style="width:188px;">R2071</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">- Direct-zol RNA PreWash</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">- RNA Wash Buffer</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">- DNase/RNase-free water</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">- Zymo-spin IIICG columns</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">- Collection Tubes</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">RT-LAMP:</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">1x SD II reaction buffer</td>
			<td style="width:224px;">Biotechrabbit</td>
			<td style="width:188px;">BR1101301</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:255px;">Magnesium sulfate (MgSO4)</td>
			<td style="width:224px;">Sigma-Aldrich</td>
			<td style="width:188px;">7487-88-9</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">dNTP set</td>
			<td style="width:224px;">Bioline</td>
			<td style="width:188px;">BIO-39053</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Betaine</td>
			<td style="width:224px;">Sigma-Aldrich</td>
			<td style="width:188px;">B2629</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">Calcein mixture</td>
			<td style="width:224px;">Merck</td>
			<td style="width:188px;">1461-15-0</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Bst DNA polymerase</td>
			<td style="width:224px;">Biotechrabbit</td>
			<td style="width:188px;">BR1101301</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">AMV reverse transcriptase</td>
			<td style="width:224px;">Promega</td>
			<td style="width:188px;">M510A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Nuclease-free water</td>
			<td style="width:224px;">Invitrogen</td>
			<td style="width:188px;">10320995</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">Elite dry bath incubator, single unit</td>
			<td style="width:224px;">Major Science</td>
			<td style="width:188px;">EL-01-220</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">Gel electrophoresis:</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Agarose</td>
			<td style="width:224px;">Vivantis Technologies</td>
			<td style="width:188px;">PC0701-500G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Tris-borate-EDTA (TBE) buffer</td>
			<td style="width:224px;">Sigma-Aldrich</td>
			<td style="width:188px;">SRE0062</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Tris-acetic-EDTA (TAE) buffer:</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">- Tris</td>
			<td style="width:224px;">Vivantis Technologies</td>
			<td style="width:188px;">PR0612-1KG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">- Acetic acid (glacial), EMSURE</td>
			<td style="width:224px;">Merck Millipore</td>
			<td style="width:188px;">1000632500</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:255px;">- Disodium Ethylenediaminetetraacetate dihydrate (EDTA), Vetec</td>
			<td style="width:224px;">Sigma-Aldrich</td>
			<td style="width:188px;">V800170-500G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Neogreen</td>
			<td style="width:224px;">NeoScience Co., Ltd.</td>
			<td style="width:188px;">GR107</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">DNA gel loading dye (6X)</td>
			<td style="width:224px;">ThermoFisher Scientific Corp.</td>
			<td style="width:188px;">R0611</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">DNA ladder and markers</td>
			<td style="width:224px;">Vivantis Technologies</td>
			<td style="width:188px;">PC701-100G</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Mini Ready Sub-Cell GT (Horizontal electrophoresis system)</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">1704487</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">PowerPac HC power supply</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">1645052</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Gel Doc EZ System</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">1708270</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">UV sample tray</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">1708271</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">N&#945;BI imager</td>
			<td style="width:224px;">Neogene Science</td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">cDNA synthesis:</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">ReverTra Ace qPCR RT Kit</td>
			<td style="width:224px;">Toyobo</td>
			<td style="width:188px;">FSQ-101</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Viva cDNA Synthesis Kit</td>
			<td style="width:224px;">Vivantis Technologies</td>
			<td style="width:188px;">cDSK01</td>
			<td>An alternative option for cDNA synthesis</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">NanoDrop2000 (microvolume spectrophotometer)</td>
			<td style="width:224px;">ThermoFisher Scientific Corp.</td>
			<td style="width:188px;">ND-2000</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">T100 Thermal Cycler</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">1861096</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">RT-qPCR:</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">iTaq Universal SYBR Green Supermix</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">1725120</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Nuclease-free water, sterile water</td>
			<td style="width:224px;">MultiCell</td>
			<td style="width:188px;">809-115-CL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">8-tube PCR strips, white</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">TLS0851</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Flat PCR tube 8-cap strips, optical</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">TCS0803</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">CFX96 Touch Thermal Cycler</td>
			<td style="width:224px;">Bio-Rad</td>
			<td style="width:188px;">1855196</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:255px;">General equipment and materials:</td>
			<td style="width:224px;"></td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Mayo scissors</td>
			<td style="width:224px;"></td>
			<td style="width:188px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Forceps</td>
			<td style="width:224px;"></td>
			<td style="width:188px;">N/A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Vortex Genie 2 (vortex mixer)</td>
			<td style="width:224px;">Scientific Industries</td>
			<td style="width:188px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Microcentrifuge LM-60</td>
			<td style="width:224px;">LioFuge</td>
			<td style="width:188px;">CM610</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Corning LSE mini microcentrifuge</td>
			<td style="width:224px;">Corning</td>
			<td style="width:188px;">6765</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Pipettes</td>
			<td style="width:224px;">Rainin</td>
			<td style="width:188px;">Pipete-Lite XLS</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">QSP filtered pipette tips</td>
			<td style="width:224px;">Quality Scientific Plastics</td>
			<td style="width:188px;">TF series</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Corning Isotip filtered tips</td>
			<td style="width:224px;">Merck</td>
			<td style="width:188px;">CLS series</td>
			<td></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:255px;">Nuclease-free 1.5 mL microcentrifuge tubes, NEST</td>
			<td style="width:224px;">Wuxi NEST Biotechnology</td>
			<td style="width:188px;">615601</td>
			<td></td>
		</tr>
	</tbody>
</table>

reverse transcription loop-mediated isothermal amplification (rt-lamp) assay for the specific and rapid detection of tilapia lake virus

Tilapia lake virus disease (TiLVD), an emerging viral disease in tilapia caused by the tilapia lake virus (TiLV), is a persistent challenge in the aquaculture industry that has resulted in the mass morbidity and mortality of tilapia in many parts of the world. An effective, rapid, and accurate diagnostic assay for TiLV infection is therefore necessary to detect the initial infection and to prevent the spread of the disease in aquaculture farming. In this study, a highly sensitive and practical reverse transcription loop-mediated isothermal amplification (RT-LAMP) method is presented to detect tilapia lake virus in fish tissue. A comparison of the RT-qPCR and RT-LAMP assays of infected samples revealed positive results in 63 (100%) and 51 (80.95%) samples, respectively. Moreover, an analysis of uninfected samples showed that all 63 uninfected tissues yielded negative results for both the RT-qPCR and RT-LAMP assays. The cross-reactivity with five pathogens in tilapia was evaluated using RT-LAMP, and all the tests showed negative results. Both the liver and mucus samples obtained from infected fish showed comparable results using the RT-LAMP method, suggesting that mucus can be used in RT-LAMP as a nonlethal assay to avoid killing fish. In conclusion, the results demonstrated that the presented RT-LAMP assay provides an effective method for TiLV detection in tilapia tissue within 1 h. The method is therefore recommended as a screening tool on farms for the rapid diagnosis of TiLV.

In this study, an RT-LAMP assay was developed to detect TiLV infection in tilapia. The tested samples were collected from 14 farms located in different parts of Thailand between 2015 and 2016. The infected and uninfected &#64257;sh were primarily grouped based on physical diagnoses and the appearances of symptomatic TiLVD. TiLV infection was subsequently con&#64257;rmed using RT-PCR after the collection process. Agarose gel electrophoresis and the detection of a luminescent green color were selected as the evaluation met...

Watch this Scientific Journal Video about Reverse Transcription Loop-Mediated Isothermal Amplification RT-LAMP Assay for the Specific and Rapid Detection of Tilapia Lake Virus at JoVE.com

Reverse Transcription Loop-Mediated Isothermal Amplification RT-LAMP Assay for the Specific and Rapid Detection of Tilapia Lake Virus

We present an RT-LAMP assay for the detection of TiLV in tilapia fish using simple instruments over a relatively short period of time compared to conventional RT-PCR techniques. This protocol may help control the epidemic spread of TiLVD, especially in developing countries.

Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) Assay for the Specific and Rapid Detection of Tilapia Lake Virus

Tilapia lake virus disease (TiLVD), an emerging viral disease in tilapia caused by the tilapia lake virus (TiLV), is a persistent challenge in the ...

reverse-transcription-loop-mediated-isothermal-amplification-rt-lamp

Universidad de Cartagena UDEC

Research

JoVE Journal

Immunology and Infection

12.6K Views.  King Mongkut's University of Technology North Bangkok (KMUTNB). We present an RT-LAMP assay for the detection of TiLV in tilapia fish using simple instruments over a relatively short period of time compared to conventional RT-PCR techniques. This protocol may help control the epidemic spread of TiLVD, especially in developing countries.

Video: Reverse Transcription Loop-Mediated Isothermal Amplification RT-LAMP Assay for the Specific and Rapid Detection of Tilapia Lake Virus

Combination of Adhesive-tape-based Sampling and Fluorescence in situ Hybridization for Rapid Detection of Salmonella on Fresh Produce

This protocol describes a simple approach for adhesive-tape-based sampling of tomato and other fresh produce surfaces, followed by on-tape fluorescence in situ hybridization (FISH) for rapid culture-independent detection of Salmonella spp. Cell-charged tapes can also be placed face-down on selective agar for solid-phase enrichment prior to detection. Alternatively, low-volume liquid enrichments (liquid surface miniculture) can be performed on the surface of the tape in non-selective broth, followed by FISH and analysis via flow cytometry. To begin, sterile adhesive tape is brought into contact with fresh produce, gentle pressure is applied, and the tape is removed, physically extracting microbes present on these surfaces. Tapes are mounted sticky-side up onto glass microscope slides and the sampled cells are fixed with 10% formalin (30 min) and dehydrated using a graded ethanol series (50, 80, and 95%; 3 min each concentration). Next, cell-charged tapes are spotted with buffer containing a Salmonella-targeted DNA probe cocktail and hybridized for 15 - 30 min at 55&deg;C, followed by a brief rinse in a washing buffer to remove unbound probe. Adherent, FISH-labeled cells are then counterstained with the DNA dye 4',6-diamidino-2-phenylindole (DAPI) and results are viewed using fluorescence microscopy. For solid-phase enrichment, cell-charged tapes are placed face-down on a suitable selective agar surface and incubated to allow in situ growth of Salmonella microcolonies, followed by FISH and microscopy as described above. For liquid surface miniculture, cell-charged tapes are placed sticky side up and a silicone perfusion chamber is applied so that the tape and microscope slide form the bottom of a water-tight chamber into which a small volume (&le; 500 &mu;L) of Trypticase Soy Broth (TSB) is introduced. The inlet ports are sealed and the chambers are incubated at 35 - 37&deg;C, allowing growth-based amplification of tape-extracted microbes. Following incubation, inlet ports are unsealed, cells are detached and mixed with vigorous back and forth pipetting, harvested via centrifugation and fixed in 10% neutral buffered formalin. Finally, samples are hybridized and examined via flow cytometry to reveal the presence of Salmonella spp. As described here, our "tape-FISH" approach can provide simple and rapid sampling and detection of Salmonella on tomato surfaces. We have also used this approach for sampling other types of fresh produce, including spinach and jalape&ntilde;o peppers.

Combination of Adhesive-tape-based Sampling and Fluorescence in situ Hybridization for Rapid Detection of Salmonella on Fresh Produce

This protocol describes a simple adhesive-tape-based approach for sampling of tomato and other fresh produce surfaces, followed by rapid whole cell detection of Salmonella using fluorescence in situ hybridization (FISH).

This protocol describes a simple approach for adhesive-tape-based sampling of tomato and other fresh produce surfaces, followed by on-tape fluorescence in ...

Detection of Infectious Virus from Field-collected Mosquitoes by Vero Cell Culture Assay

Mosquitoes transmit a number of distinct viruses including important human pathogens such as West Nile virus, dengue virus, and chickungunya virus. Many of these viruses have intensified in their endemic ranges and expanded to new territories, necessitating effective surveillance and control programs to respond to these threats. One strategy to monitor virus activity involves collecting large numbers of mosquitoes from endemic sites and testing them for viral infection. In this article, we describe how to handle, process, and screen field-collected mosquitoes for infectious virus by Vero cell culture assay. Mosquitoes are sorted by trap location and species, and grouped into pools containing &le;50 individuals. Pooled specimens are homogenized in buffered saline using a mixer-mill and the aqueous phase is inoculated onto confluent Vero cell cultures (Clone E6). Cell cultures are monitored for cytopathic effect from days 3-7 post-inoculation and any viruses grown in cell culture are identified by the appropriate diagnostic assays. By utilizing this approach, we have isolated 9 different viruses from mosquitoes collected in Connecticut, USA, and among these, 5 are known to cause human disease. Three of these viruses (West Nile virus, Potosi virus, and La Crosse virus) represent new records for North America or the New England region since 1999. The ability to detect a wide diversity of viruses is critical to monitoring both established and newly emerging viruses in the mosquito population.

We describe a method to process and screen field-collected mosquitoes for a diversity of viruses by Vero cell culture assay. By employing this technique, we have detected 9 different viruses from 4 taxonomic families in mosquitoes collected in Connecticut.

Mosquitoes transmit a number of distinct viruses including important human pathogens such as West Nile virus, dengue virus, and chickungunya virus. Many ...

Microwave Assisted Rapid Diagnosis of Plant Virus Diseases by Transmission Electron Microscopy

Investigations of ultrastructural changes induced by viruses are often necessary to clearly identify viral diseases in plants. With conventional sample preparation for transmission electron microscopy (TEM) such investigations can take several days1,2 and are therefore not suited for a rapid diagnosis of plant virus diseases. Microwave fixation can be used to drastically reduce sample preparation time for TEM investigations with similar ultrastructural results as observed after conventionally sample preparation3-5. Many different custom made microwave devices are currently available which can be used for the successful fixation and embedding of biological samples for TEM investigations5-8. In this study we demonstrate on Tobacco Mosaic Virus (TMV) infected Nicotiana tabacum plants that it is possible to diagnose ultrastructural alterations in leaves in about half a day by using microwave assisted sample preparation for TEM. We have chosen to perform this study with a commercially available microwave device as it performs sample preparation almost fully automatically5 in contrast to the other available devices where many steps still have to be performed manually6-8 and are therefore more time and labor consuming. As sample preparation is performed fully automatically negative staining of viral particles in the sap of the remaining TMV-infected leaves and the following examination of ultrastructure and size can be performed during fixation and embedding.

This study describes a method that allows the rapid and clear diagnosis of plant virus diseases in about half a day by using a combination of microwave assisted plant sample preparation for transmission electron microscopy and negative staining methods.

Investigations of ultrastructural changes induced by viruses are often necessary to clearly identify viral diseases in plants. With conventional sample ...

High-throughput Detection Method for Influenza Virus

Influenza virus is a respiratory pathogen that causes a high degree of morbidity and mortality every year in multiple parts of the world. Therefore, precise diagnosis of the infecting strain and rapid high-throughput screening of vast numbers of clinical samples is paramount to control the spread of pandemic infections. Current clinical diagnoses of influenza infections are based on serologic testing, polymerase chain reaction, direct specimen immunofluorescence and cell culture 1,2.
Here, we report the development of a novel diagnostic technique used to detect live influenza viruses. We used the mouse-adapted human A/PR/8/34 (PR8, H1N1) virus 3 to test the efficacy of this technique using MDCK cells 4. MDCK cells (104 or 5 x 103 per well) were cultured in 96- or 384-well plates, infected with PR8 and viral proteins were detected using anti-M2 followed by an IR dye-conjugated secondary antibody. M2 5 and hemagglutinin 1 are two major marker proteins used in many different diagnostic assays. Employing IR-dye-conjugated secondary antibodies minimized the autofluorescence associated with other fluorescent dyes. The use of anti-M2 antibody allowed us to use the antigen-specific fluorescence intensity as a direct metric of viral quantity. To enumerate the fluorescence intensity, we used the LI-COR Odyssey-based IR scanner. This system uses two channel laser-based IR detections to identify fluorophores and differentiate them from background noise. The first channel excites at 680 nm and emits at 700 nm to help quantify the background. The second channel detects fluorophores that excite at 780 nm and emit at 800 nm. Scanning of PR8-infected MDCK cells in the IR scanner indicated a viral titer-dependent bright fluorescence. A positive correlation of fluorescence intensity to virus titer starting from 102-105 PFU could be consistently observed. Minimal but detectable positivity consistently seen with 102-103 PFU PR8 viral titers demonstrated the high sensitivity of the near-IR dyes. The signal-to-noise ratio was determined by comparing the mock-infected or isotype antibody-treated MDCK cells.
Using the fluorescence intensities from 96- or 384-well plate formats, we constructed standard titration curves. In these calculations, the first variable is the viral titer while the second variable is the fluorescence intensity. Therefore, we used the exponential distribution to generate a curve-fit to determine the polynomial relationship between the viral titers and fluorescence intensities. Collectively, we conclude that IR dye-based protein detection system can help diagnose infecting viral strains and precisely enumerate the titer of the infecting pathogens.

This method describes the use of Infrared dye based imaging system for detection of H1N1 in bronchioalveolar lavage (BAL) fluid of infected mice at a high sensitivity. This methodology can be performed in a 96- or 384-well plate, requires &lt;10 &mu;l volume of test material and has the potential for concurrent screening of multiple pathogens.

Influenza virus is a respiratory pathogen that causes a high degree of morbidity and mortality every year in multiple parts of the world. Therefore, ...

Rapid Screening of HIV Reverse Transcriptase and Integrase Inhibitors

Although a number of anti HIV drugs have been approved, there are still problems with toxicity and drug resistance. This demonstrates a need to identify new compounds that can inhibit infection by the common drug resistant HIV-1 strains with minimal toxicity. Here we describe an efficient assay that can be used to rapidly determine the cellular cytotoxicity and efficacy of a compound against WT and mutant viral strains.
The desired target cell line is seeded in a 96-well plate and, after a 24 hr incubation, serially dilutions of the compounds to be tested are added. No further manipulations are necessary for cellular cytotoxicity assays; for anti HIV assays a predetermined amount of either a WT or drug resistant HIV-1 vector that expresses luciferase is added to the cells. Cytotoxicity is measured by using an ATP dependent luminescence assay and the impact of the compounds on infectivity is measured by determining the amount of luciferase in the presence or the absence of the putative inhibitors.
This screening assay takes 4 days to complete and multiple compounds can be screened in parallel. Compounds are screened in triplicate and the data are normalized to the infectivity/ATP levels in absence of target compounds. This technique provides a quick and accurate measurement of the efficacy and toxicity of potential anti HIV compounds.

Here we describe cellular cytotoxicity and single round infectivity assays that allow for the rapid and accurate screening of compounds to determine their cellular cytotoxicity (CC50) and IC50 values against WT and drug resistant HIV-1.

Although a number of anti HIV drugs have been approved, there are still problems with toxicity and drug resistance. This demonstrates a need to identify ...

Loop-mediated Isothermal Amplification (LAMP) Assays for the Species-specific Detection of Eimeria that Infect Chickens

Eimeria species parasites, protozoa which cause the enteric disease coccidiosis, pose a serious threat to the production and welfare of chickens. In the absence of effective control clinical coccidiosis can be devastating. Resistance to the chemoprophylactics frequently used to control Eimeria is common and sub-clinical infection is widespread, influencing feed conversion ratios and susceptibility to other pathogens such as Clostridium perfringens. Despite the availability of polymerase chain reaction (PCR)-based tools, diagnosis of Eimeria infection still relies almost entirely on traditional approaches such as lesion scoring and oocyst morphology, but neither is straightforward. Limitations of the existing molecular tools include the requirement for specialist equipment and difficulties accessing DNA as template. In response a simple field DNA preparation protocol and a panel of species-specific loop-mediated isothermal amplification (LAMP) assays have been developed for the seven Eimeria recognised to infect the chicken. We now provide a detailed protocol describing the preparation of genomic DNA from intestinal tissue collected post-mortem, followed by setup and readout of the LAMP assays. Eimeria species-specific LAMP can be used to monitor parasite occurrence, assessing the efficacy of a farm&#8217;s anticoccidial strategy, and to diagnose sub-clinical infection or clinical disease with particular value when expert surveillance is unavailable.

Loop-mediated Isothermal Amplification LAMP Assays for the Species-specific Detection of Eimeria that Infect Chickens

Diagnosis of Eimeria infection in chickens remains demanding. Parasite morphology- and host pathology-led approaches are commonly inconclusive, while molecular approaches based on PCR have proven demanding in cost and expertise. The aim of this protocol is to establish loop-mediated isothermal amplification (LAMP) as a straightforward molecular diagnostic for eimerian infection.

Eimeria species parasites, protozoa which cause the enteric disease coccidiosis, pose a serious threat to the production and welfare of chickens. In the ...

Nasal Wipes for Influenza A Virus Detection and Isolation from Swine

Surveillance for influenza A viruses in swine is critical to human and animal health because influenza A virus rapidly evolves in swine populations and new strains are continually emerging. Swine are able to be infected by diverse lineages of influenza A virus making them important hosts for the emergence and maintenance of novel influenza A virus strains. Sampling pigs in diverse settings such as commercial swine farms, agricultural fairs, and live animal markets is important to provide a comprehensive view of currently circulating IAV strains. The current gold-standard ante-mortem sampling technique (i.e. collection of nasal swabs) is labor intensive because it requires physical restraint of the pigs. Nasal wipes involve rubbing a piece of fabric across the snout of the pig with minimal to no restraint of the animal. The nasal wipe procedure is simple to perform and does not require personnel with professional veterinary or animal handling training. While slightly less sensitive than nasal swabs, virus detection and isolation rates are adequate to make nasal wipes a viable alternative for sampling individual pigs when low stress sampling methods are required. The proceeding protocol outlines the steps needed to collect a viable nasal wipe from an individual pig.

The authors present a protocol to collect swine nasal wipes to detect and isolate influenza A viruses.

Surveillance for influenza A viruses in swine is critical to human and animal health because influenza A virus rapidly evolves in swine populations and ...

The Development of Lyophilized Loop-mediated Isothermal Amplification Reagents for the Detection of Coxiella burnetii

Coxiella burnetii, the agent causing Q fever, is an obligate intracellular bacterium. PCR based diagnostic assays have been developed for detecting C. burnetii DNA in cell cultures and clinical samples. PCR requires specialized equipment and extensive end user training, and therefore, it is not suitable for routine work especially in a resource-constrained area. We have developed a loop-mediated isothermal amplification (LAMP) assay to detect the presence of C. burnetii in patient samples. This method is performed at a single temperature around 60 &#176;C in a water bath or heating block. The sensitivity of this LAMP assay is very similar to PCR with a detection limit of about 25 copies per reaction. This report describes the preparation of the reaction using lyophilized reagents and visualization of results using hydroxynaphthol blue (HNB) or a UV lamp with fluorescent intercalating dye in the reaction. The LAMP reagents were lyophilized and stored at room temperature (RT) for one month without loss of detection sensitivity. This LAMP assay is particularly robust because the reaction mixture preparation does not involve complex steps. This method is ideal for use in resource-limited settings where Q fever is endemic.

The Development of Lyophilized Loop-mediated Isothermal Amplification Reagents for the Detection of Coxiella burnetii

We described here a simple loop-mediated isothermal amplification (LAMP) method using lyophilized reagents for the detection of C. burnetii in patient samples.

Coxiella burnetii, the agent causing Q fever, is an obligate intracellular bacterium. PCR based diagnostic assays have been developed for detecting C. ...

In Vivo Assay for Detection of Antigen-specific T-cell Cytolytic Function Using a Vaccination Model

Current methodologies for antigen-specific killing are limited to in vitro use or utilized in infectious disease models. However, there is not a protocol specifically intended to measure antigen-specific killing without an infection. This protocol is designed and describes methods to overcome these limitations by allowing for the detection of antigen-specific killing of a target cell by CD8+ T cells in vivo. This is accomplished by merging a vaccination model with a traditional CFSE-labeled target killing assay. This combination allows the researcher to assess the antigen-specific CTL potential directly and quickly as the assay is not dependent upon tumor growth or infection. In addition, the readout is based on flow cytometry and so should be readily accessible to most researchers. The major limitation of the study is identifying the timeline in vivo that is appropriate to the hypothesis being tested. Variations in antigen strength and mutations in the T cells that may result in differential cytolytic function need to be carefully assessed to determine the optimal time for cell harvest and assessment. The appropriate concentration of peptide for vaccination has been optimized for hgp10025-33 and OVA257-264, but further validation would be needed for other peptides that may be more appropriate to a given study. Overall, this protocol allows a quick assessment of killing function in vivo and can be adapted to any given antigen.

In Vivo Assay for Detection of Antigen-specific T-cell Cytolytic Function Using a Vaccination Model

The goal of this protocol is to allow for detection of in vivo antigen-specific killing of a target cell in a murine model.

Current methodologies for antigen-specific killing are limited to in vitro use or utilized in infectious disease models. However, there is not a protocol ...

Zika Virus Specific Diagnostic Epitope Discovery

High-density peptide microarrays allow screening of more than six thousand peptides on a single standard microscopy slide. This method can be applied for drug discovery, therapeutic target identification, and developing of diagnostics. Here, we present a protocol to discover specific Zika virus (ZIKV) diagnostic peptides using a high-density peptide microarray. A human serum sample validated for ZIKV infection was incubated with a high-density peptide microarray containing the entire ZIKV protein translated into 3,423 unique 15 linear amino acid (aa) residues with a 14-aa residue overlap printed in duplicate. Staining with different secondary antibodies within the same array, we detected peptides that bind to Immunoglobulin M (IgM) and Immunoglobulin G (IgG) antibodies present in serum. These peptides were selected for further validation experiments. In this protocol, we describe the strategy followed to design, process, and analyze a high-density peptide microarray.

In this protocol, we describe a technique to discover Zika virus specific diagnostic peptides using a high-density peptide microarray. This protocol can readly be adapted for other emerging infectious diseases.

High-density peptide microarrays allow screening of more than six thousand peptides on a single standard microscopy slide. This method can be applied for ...

Reverse Transcription Loop-Mediated Isothermal Amplification (RT-LAMP) Assay for the Specific and Rapid Detection of Tilapia Lake Virus

Summary

Explore More Videos

Chapters in this video

Combination of Adhesive-tape-based Sampling and Fluorescence in situ Hybridization for Rapid Detection of Salmonella on Fresh Produce

Detection of Infectious Virus from Field-collected Mosquitoes by Vero Cell Culture Assay

Microwave Assisted Rapid Diagnosis of Plant Virus Diseases by Transmission Electron Microscopy

High-throughput Detection Method for Influenza Virus

Rapid Screening of HIV Reverse Transcriptase and Integrase Inhibitors

Loop-mediated Isothermal Amplification (LAMP) Assays for the Species-specific Detection of Eimeria that Infect Chickens

Nasal Wipes for Influenza A Virus Detection and Isolation from Swine

The Development of Lyophilized Loop-mediated Isothermal Amplification Reagents for the Detection of Coxiella burnetii

In Vivo Assay for Detection of Antigen-specific T-cell Cytolytic Function Using a Vaccination Model

Zika Virus Specific Diagnostic Epitope Discovery