Novel high-performance detection of Raillietina echinobothrida, Raillietina tetragona, and Raillietina cesticillus using loop-mediated isothermal amplification coupled with a lateral flow dipstick (LAMP-LFD)

A simple color absorption analysis of colorimetric loop-mediated isothermal amplification for detection of Raillietina spp. in clinical samples using a 3D-printed tube holder coupled with a smartphone camera and notebook screen

A simple method has been developed for semi-quantitative analysis of the colorimetric output of loop-mediated isothermal amplification (LAMP) using a 3D-printed tube holder with a smartphone and notebook for the detection of Raillietina, which is the cause of Raillietiniasis affecting free-range chicken farming. In this method, a light is directed from a notebook screen to the LAMP products in the tube holder and the color absorption of the LAMP products is measured by using the appropriate smartphone application. It was found that the malachite green dye-coupled LAMP (MaG-LAMP) assay showed the highest sensitivity and specificity for detecting Raillietina without any cross-reaction with other related parasites and hosts. The limit of detection was 10 fg/μL of DNA. A total of 60 fecal samples were infectively confirmed by microscopic examination and the results of microscopy compared with those of MaG-LAMP and triplex PCR assays. Microscopy and MaG-LAMP based on the color absorption demonstrated high agreement in Raillietina detection with kappa = 1. Rapid, simple, cost-effective, and easy interpretation of colorimetric LAMP assays and their high sensitivity make them superior to PCR and morphological investigation, demonstrating the feasibility of this assay in point-of-care screening to support farm management and solve chicken health problems. Our study presents is an alternative diagnostic method using semi-quantitative analysis of colorimetric LAMP based on the differing solution color absorptions between positive and negative reactions for infectious disease diagnosis.

Assay for the simultaneous detection of Raillietina spp. (R. echinobothrida, R. tetragona, and R. cesticillus) and Ascaridia galli infection in chickens using duplex loop-mediated isothermal amplification integrated with a lateral flow dipstick assay

Raillietina species and Ascaridia galli are two of the significant intestinal parasites that affect chickens in a free-range system production. They destroy the intestinal mucosa layer, leading to several clinical symptoms such as weight loss, a slowed growth rate, and economic value loss. Thus, the objective of this study was to develop an assay for simultaneously detecting Raillietina spp. (R. echinobothrida, R. tetragona, and R. cesticillus) and A. galli in a single reaction using duplex loop-mediated isothermal amplification (dLAMP) coupled with a lateral flow dipstick (LFD) assay. The analytical specificity of the dLAMP-LFD assay showed a high specific amplification of Raillietina spp. and A. galli without non-target amplification. Regarding the analytical sensitivity, this approach was capable of simultaneously detecting concentrations as low as 5 pg/μL of mixed-targets. To evaluate the efficiency of the dLAMP assay, 30 faecal samples of chickens were verified and compared through microscopic examination. The dLAMP-LFD assay and microscopic examination results showed kappa values of Raillietina spp. and A. galli with moderate (K= 0.615) to high (K= 1) agreements, respectively, while the McNemar's test indicated that the efficiency between assays was not significantly different. Therefore, the developed dLAMP-LFD assay can be used as an alternative screening method to the existing classical method for epidemiological investigation, epidemic control, and farm management, as well as for addressing poultry health problems.

Evaluation of semi-quantitative colorimetric assays based on loop-mediated isothermal amplification indicators by using image analysis

Colorimetric assays are some of the most convenient detection methods, creating discoloration in solutions that is visible to the naked eye. However, colorimetric reactions have some limitations regarding the variability in the color perception of individuals caused by factors such as color blindness, experience, and gender. Semi-quantitative chromatic analysis has been used as an alternative method to differentiate between two colors and accurately interpret the results from a numerical value, with high confidence. Therefore, we developed and determined the optimal model between Red-Green-Blue (RGB) and Commission Internationale de l'Eclairage (CIE) Lab color spaces to establish a semi-quantitative colorimetric assay via image analysis by the ImageJ program for loop-mediated isothermal amplification (LAMP), using the dyes malachite green and phenol red. The semi-quantitative colorimetric assays using the color distance values of the CIELab color space (ΔEab) were more suitable than those using the RGB color space (ΔERGB) for chromatic differentiation between positive and negative reactions in both indicator dyes, demonstrating the feasibility of this assay to be applied in the detection of a wide range of pathogens and infectious diseases.

Feasibility of a DNA biosensor assay based on loop-mediated isothermal amplification combined with a lateral flow dipstick assay for the visual detection of Ascaridia galli eggs in faecal samples

Ascaridia galli is an important nematode that causes ascaridiasis in free-range and indoor system chicken farms. Infection with A. galli may damage the intestinal mucosa and inhibit nutrient absorption, leading to a reduced growth rate, weight loss and a decreased egg production. Consequently, A. galli infection is a significant health problem in chickens. In this study, we developed a loop-mediated isothermal amplification coupled with a lateral flow dipstick (LAMP-LFD) assay for the visual detection of A. galli eggs in faecal samples. The LAMP-LFD assay consists of six primers and one DNA probe that recognize the internal transcribed spacer 2 (ITS2) region; it can be performed within 70 min and the results can be interpreted with the naked eye. Using the LAMP-LFD assay developed in this study, A. galli DNA was specifically amplified without any cross-reactions with other related parasites (Heterakis gallinarum, Raillietina echinobothrida, R. tetragona, R. cesticillus, Cotugnia sp., Echinostoma miyagawai) and definitive hosts (Gallus gallus domesticus, Anas platyrhynchos domesticus). The minimum detectable DNA concentration was 5 pg/μl, and the detectable egg count was 50 eggs per reaction. The assay can be performed in a water bath, without the need for post-mortem morphological investigations and laboratory instruments. It is therefore a viable alternative for the detection of A. galli in chicken faeces and can replace classical methods in field screening for epidemiological investigations, veterinary health and poultry farming management. RESEARCH HIGHLIGHTSThis is the first study using the LAMP-LFD assay for Ascaridia galli detection.The results can be observed by the naked eye.The developed assay can be used to detect Ascaridia galli eggs in faecal samples.

Multi-detection for paramphistomes using novel manually designed PAR-LAMP primers and its application in a lateral flow dipstick (LAMP-LFD) system

Loop-mediated isothermal amplification (LAMP) has been applied for the detection of various parasites, and its application in lateral flow dipstick (LFD) can improve the convenience of point-of-care diagnosis. A novel PAR-LAMP probe and primers were designed by manual selection from a region of low variation in the ITS-2 DNA sequence. Up to six species of rumen fluke were detected by LAMP and LAMP-LFD in this study. Target specificity and sensitivity were tested, revealing a high target specificity (accuracy) and a low limit of detection (sensitivity). Different target sensitivities of paramphistome were presented, including 5 pg for Gastrothylax crumenifer and Carmyerius sp.; 1 pg for Fischoederius elongatus, Orthocoelium parvipapillatum, and O. dicranocoelium; and 0.1 pg for Paramphistomum epiclitum. LAMP-LFD can detect a paramphistome egg even in contaminated in feces that was spiked with the egg under laboratory conditions. In addition, natural paramphistome infection in cattle from Surat Thani and Khon Kaen provinces, Thailand, was evaluated by detection of egg contamination in fecal specimens using PAR-LAMP primers. The PAR-LAMP detection result was also statistically evaluated by microscopic examination of feces. This study presents the application of novel manually designed primers in a LAMP-LFD system for improving performance in detection and diagnosis assays for paramphistomosis.

High-performance triplex PCR detection of three tapeworm species belonging to the genus Raillietina in infected poultry

Chickens and ducks are important sources of essential proteins and nutrition for global consumption, especially their eggs and meat. Tapeworm infections in chickens and ducks are the cause of serious poultry health and economic problems in the processing of livestock and food production systems. Raillietina are cosmopolitan in distribution and are possibly the most common tapeworm parasites. There are three important species regarding avian infection, with different pathogenicity, including Raillietina echinobothrida, R. tetragona, and R. cesticillus. Co-infection diagnosis of these tapeworms using morphological analysis can be performed, but this is time-consuming and complicated. Therefore, this study aimed to develop a triplex PCR for the detection and discrimination of three Raillietina species. The triplex PCR assay specifically amplified target DNAs with no inter-specific interference and produced a specific band for each species. According to the specificity test, there was no cross-amplification with the DNA template of related parasites and their hosts. The lowest detectable DNA concentrations were evaluated and provided sensitivities of 0.5 pg/μL for R. echinobothrida, 5 pg/μL for R. tetragona, 50 fg/μL for R. cesticillus, and 5 pg/μL for the combination of DNA from all three species. Simultaneous detection limits of egg capsules and gravid proglottids was also performed, with and without feces. The interference of feces in the reaction was related to a decrease in sensitivity, but simultaneous detection of three Raillietina species in amounts lower than one gravid proglottid and ten egg capsules was still successful. Thus, this study is the first triplex PCR assay for Raillietina detection and can be utilized as an alternative diagnostic tool for the detection and discrimination of R. echinobothrida, R. tetragona, and R. cesticillus infection in poultry through the verification of fecal specimens. In addition, it could improve the performance of specific treatments and promote veterinary healthcare.

Molecular detection of three intestinal cestode species (Raillietina echinobothrida, R. tetragona, R. cesticillus) from poultry in Thailand

RESEARCH HIGHLIGHTS

This study established specific primers for Raillietina species detection.The ITS2 region is an effective molecular marker for Raillietina identification.