Detection and quantification of Wuchereria bancrofti and Brugia malayi DNA in blood samples and mosquitoes using duplex droplet digital polymerase chain reaction

Beyond Tradition: Exploring Cutting-Edge Approaches for Accurate Diagnosis of Human Filariasis

Filariasis is recognised as a global public health threat, particularly in tropical and subtropical regions. It is caused by infection with a nematode parasite of the superfamily Filarioidea, including Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus, and Onchocerca lupi. Three main types of filariasis have been classified: lymphatic filariasis, subcutaneous filariasis, and serous cavity filariasis. The symptoms exhibited by individuals afflicted with filariasis are diverse and contingent upon several variables, including the species of parasite, the host's health and immune response, and the stage of infection. While many classical parasitological techniques are considered indispensable tools for the diagnosis of parasitic infections in humans, alternative methods are being sought due to their limitations. Novel tests based on host-parasite interactions offer a rapid, simple, sensitive, and specific diagnostic tool in comparison to traditional parasitological methods. This article presents methods developed in the 21st century for the diagnosis of filariasis caused by invasion from W. bancrofti, B. malayi, O. volvulus, and O. lupi, as well as techniques that are currently in use. The development of modern diagnostic methods based on molecular biology constitutes a significant advancement in the fight against filariasis.

A newly developed droplet digital PCR for Ehrlichia canis detection: comparisons to conventional PCR and blood smear techniques

Canine monocytic ehrlichiosis caused by Ehrlichia canis infection is a life-threatening vector-borne disease in dogs worldwide. Routine blood smear has very low sensitivity and cannot accurately provide a quantitative result. Conventional PCR (cPCR) and real-time PCR (qPCR) are widely used as molecular methods for E. canis detection. qPCR is quantitative but relies on standard curves of known samples. To overcome this difficulty, this study developed a new E. canis quantitative detection method, using droplet digital polymerase chain reaction (ddPCR). ddPCR was evaluated against cPCR and blood smears. PCR amplicons and genomic DNA (gDNA) from 12 microscopic positive samples were used to identify the limits of detection (LODs) in ddPCR and cPCR. Our ddPCR was assessed in 92 field samples, it was compared with cPCR and blood smears. ddPCR showed LOD = 1.6 copies/reaction, or 78 times more sensitive than cPCR (LOD = 126 copies/reaction), using PCR amplicons as a template, whereas both ddPCR and cPCR had equal LODs at 0.02 ng gDNA/reaction. In addition, ddPCR had 100% sensitivity and 75% specificity for E. canis detection compared to cPCR and no cross-reaction with other blood pathogens was observed. ddPCR identified more positive samples than cPCR and blood smear. ddPCR improved the overall performance of E. canis detection, with a better LOD and comparable sensitivity and specificity to cPCR. The technique might be helpful for diagnosis of E. canis in light infection, evaluating the number of E. canis and follow-up after treatment.

Digital PCR for accurate quantification of pathogens: Principles, applications, challenges and future prospects

Pathogens pose a severe threat to food safety and human health. The traditional methods for pathogen detection can't meet the growing diagnosis and control need. Digital PCR (dPCR) attracts a considerable attention for its ability to absolutely quantify pathogens with features of high selectivity, simplicity, accuracy and rapidity. The dPCR technique that achieves absolute quantification based on end-point measurement without standard curve offers a guideline for further genetic analysis and molecular diagnosis. It could contribute to the quantification of low level of nucleic acid, early detection and timely prevention of pathogenic diseases. In this review, 1442 publications about dPCR were selected and the detections of various pathogens by dPCR were reviewed comprehensively, including viruses, bacteria, parasites and fungi. A number of examples are cited to illustrate that dPCR is a new powerful tool with desired accuracy, sensitivity, and reproducibility for quantification of different types of pathogens. Moreover, the benefits, challenges and future prospects of the dPCR were also highlighted in this review.

Recent advances in nucleic acid-based methods for detection of helminth infections and the perspective of biosensors for future development

Pathogenic helminth infections are responsible for severe health problems and economic losses worldwide. Timely and accurate diagnosis of helminth infections is critical for adopting suitable strategies for pathogen control. Here, we review recent advances in nucleic acid-based diagnostic methods, including polymerase chain reaction, quantitative qPCR, loop-mediated isothermal amplification and recombinase polymerase amplification, and discuss their advantages and disadvantages for diagnosing helminth infections. In addition, we highlight recent advances in biosensors for the detection of nucleic acid biomarkers that can potentially be used for the diagnosis of helminth infection.

DNA Diagnostics for Schistosomiasis Control

Despite extensive efforts over the last few decades, the global disease burden of schistosomiasis still remains unacceptably high. This could partly be attributed to the lack of accurate diagnostic tools for detecting human and animal schistosome infections in endemic areas. In low transmission and low prevalence areas where schistosomiasis elimination is targeted, case detection requires a test that is highly sensitive. Diagnostic tests with low sensitivity will miss individuals with low infection intensity and these will continue to contribute to transmission, thereby interfering with the efficacy of the control measures operating. Of the many diagnostic approaches undertaken to date, the detection of schistosome DNA using DNA amplification techniques including polymerase chain reaction (PCR) provide valuable adjuncts to more conventional microscopic and serological methods, due their accuracy, high sensitivity, and the capacity to detect early pre-patent infections. Furthermore, DNA-based methods represent important screening tools, particularly in those endemic areas with ongoing control where infection prevalence and intensity have been reduced to very low levels. Here we review the role of DNA diagnostics in the path towards the control and elimination of schistosomiasis.

The History of Bancroftian Lymphatic Filariasis in Australasia and Oceania: Is There a Threat of Re-Occurrence in Mainland Australia?

Lymphatic filariasis (LF) infects an estimated 120 million people worldwide, with a further 856 million considered at risk of infection and requiring preventative chemotherapy. The majority of LF infections are caused by Wuchereria bancrofti, named in honour of the Australian physician Joseph Bancroft, with the remainder due to Brugia malayi and B. timori. Infection with LF through the bite of an infected mosquito, can lead to the development of the condition known as elephantiasis, where swelling due to oedema leads to loss of function in the affected area and thickening of the skin, 'like an elephant'. LF has previously been endemic in Australia, although currently, no autochthonous cases occur there. Human immigration to Australia from LF-endemic countries, including those close to Australia, and the presence of susceptible mosquitoes that can act as suitable vectors, heighten the possibility of the reintroduction of LF into this country. In this review, we examine the history of LF in Australia and Oceania and weigh up the potential risk of its re-occurrence on mainland Australia.

Sensitive and accurate quantification of human malaria parasites using droplet digital PCR (ddPCR)

Accurate quantification of parasite density in the human host is essential for understanding the biology and pathology of malaria. Semi-quantitative molecular methods are widely applied, but the need for an external standard curve makes it difficult to compare parasite density estimates across studies. Droplet digital PCR (ddPCR) allows direct quantification without the need for a standard curve. ddPCR was used to diagnose and quantify P. falciparum and P. vivax in clinical patients as well as in asymptomatic samples. ddPCR yielded highly reproducible measurements across the range of parasite densities observed in humans, and showed higher sensitivity than qPCR to diagnose P. falciparum, and equal sensitivity for P. vivax. Correspondence in quantification was very high (>0.95) between qPCR and ddPCR. Quantification between technical replicates by ddPCR differed 1.5-1.7-fold, compared to 2.4-6.2-fold by qPCR. ddPCR facilitates parasite quantification for studies where absolute densities are required, and will increase comparability of results reported from different laboratories.