Environmental detection of Fasciola hepatica by loop-mediated isothermal amplification

Advancing schistosomiasis surveillance: standardization and application of an environmental DNA (eDNA)-based approach for detecting Schistosoma mansoni in Brazil

BACKGROUND

Schistosoma sp. transmission is linked to water bodies, poor sanitation, and the presence of intermediate hosts. Nevertheless, parasite detection in snails is hampered by challenges in snail sampling and low infection rates, mainly in moderate and low-endemic areas, as well as requiring specialized personnel and being time-consuming. Thus, there is a need to improve tools to assist schistosomiasis surveillance and an environmental DNA (eDNA) approach may help to overcome these limitations. Here, we standardized and used an eDNA-based approach to monitor Schistosoma mansoni occurrence in two schistosomiasis endemic areas from Minas Gerais, Brazil.

METHODS

The eDNA approach was standardized for local conditions by evaluating the specificity of the qPCR assay in detecting the parasite DNA. Water from snail breeding tanks containing Biomphalaria glabrata, either infected or not with S. mansoni, was used to standardize the eDNA filtration and extraction protocols. Three molecular techniques- Low-Stringency PCR (LS-PCR), Loop-mediated isothermal amplification (LAMP), and quantitative PCR (qPCR)- were applied to investigate samples from snail tanks and two field surveys. Additionally, malacological surveys and measurements of water physicochemical and microbiological parameters were conducted at the same locations to know the species of mollusks present and the ideal environmental conditions to identify hotspots.

RESULTS

The qPCR assay was specifically amplified Schistosoma sp. DNA without amplifying other trematodes presents in Brazil, ensuring accurate detection without cross-amplification. All three molecular assays efficiently detected S. mansoni DNA only from eDNA samples from tanks with infected snails. The eDNA approach, associated with LAMP and qPCR assays, successfully identified S. mansoni DNA at the same collection points where snails releasing cercariae were found and at one additional site, that was missed by traditional methods, underscoring its sensitivity.

CONCLUSIONS

This study illustrates the potential of employing eDNA sampling combined with molecular techniques as an effective strategy for monitoring and identifying potential schistosomiasis transmission foci in endemic areas. This approach aligns with the WHO's roadmap for schistosomiasis elimination by 2030 and has implications for public health interventions and control measures.

Independent origins and non-parallel selection signatures of triclabendazole resistance in Fasciola hepatica

Triclabendazole (TCBZ) is the primary treatment for fascioliasis, a global foodborne zoonosis caused by Fasciola hepatica. Widespread resistance to TCBZ (TCBZ-R) in livestock and a rapid rise in resistant human infections are significant concerns. To understand the genetic basis of TCBZ-R, we sequenced the genomes of 99 TCBZ-sensitive (TCBZ-S) and 210 TCBZ-R adult flukes from 146 bovine livers in Cusco, Peru. We identify genomic regions of high differentiation (FST outliers above the 99.9th percentile) that encod genes involved in the EGFR-PI3K-mTOR-S6K pathway and microtubule function. Transcript expression differences are observed in microtubule-related genes between TCBZ-S and -R flukes, both without drug treatment and in response to treatment. Using only 30 SNPs, it is possible to differentiate between TCBZ-S and -R parasites with ≥75% accuracy. Our outlier loci are distinct from the previously reported TCBZ-R-associated QTLs in the UK, suggesting an independent evolution of resistance alleles. Effective genetics-based TCBZ-R surveillance must consider the heterogeneity of loci under selection across diverse geographical populations.

Conventional and Advanced Methods Used for the Diagnosis of Fascioliosis, a Food-Borne Zoonotic Disease

Fascioliosis is a food-borne zoonotic helminth infection caused by flatworms belonging to the family Fasciolidae, primarily affecting ruminants. The chronic form of fascioliosis is the most prevalent and is characterized by anemia, weight loss, cirrhosis, and liver dysfunction, along with atrophy, jaundice, and bottle jaw. In humans, infection results in fever, nausea, skin rashes, and severe abdominal pain. Climate changes and human-driven environmental alterations have contributed to an increasing incidence of fascioliosis in various regions. Fasciola species are widely distributed and have a high occurrence in tropical countries. Approximately 2.4-17 million humans are afflicted by fascioliosis in tropical and subtropical areas, with an additional 180 million facing the risk of infection. Fascioliosis poses a notable threat to ruminants; over 700 million production animals are at risk, and global annual financial losses surpass $3.2 billion. Conventional coprological methods and advanced molecular techniques are employed to diagnose fascioliosis in animals and humans. Within endemic areas, timely and accurate diagnosis is critical for successful prevention and treatment. Molecular approaches such as various PCR techniques and serological methods are extensively utilized to diagnose fascioliosis. In this review, we describe various conventional coprological and advanced DNA-based PCR techniques along with serological methods used for the screening, monitoring, and specific diagnosis of clinical and subclinical fascioliosis in humans and animals. The information accumulated in this review will be helpful for the diagnosis of fascioliosis in the field and research laboratories.

Rapid and multiple visual detection of Fasciola hepatica in feces via recombinase polymerase amplification integrated with CRISPR/Cas12a technology

Fasciola hepatica is a foodborne zoonotic parasite causing significant economic losses and impacting human and livestock health in resource-limited regions. We developed a rapid, reliable, and sensitive detection method combining recombinase polymerase amplification (RPA) with CRISPR/Cas12a, allowing visualization with the naked eye or a fluorescence reader. Multiple visual methods were used to analyze the assay results. Fluorescence signals were collected using a fluorescence reader or observed under UV or blue light. Lateral flow strips (LFS) were used for visual detection. Among seven primer pairs and three CRISPR RNA (crRNA) screened, F1/R1 and crRNA3 were optimal. The Cas12a reaction buffer was optimized with 50 mM Tris-HCl and 80 mM NaCl, with an RPA reaction time of 20 min. The assay showed high specificity and excellent sensitivity for F. hepatica, detecting 0.122 copies/μL with fluorescence and 8.6 copies/μL with LFS. Testing of 143 sheep and 43 human fecal samples showed 98.39 % consistency with qPCR and nested PCR, with prevalence rates of 52.45 % and 18.6 % in sheep and humans, respectively. Our assay offers substantial potential for point-of-care testing in resource-limited areas, addressing the need for rapid and accurate diagnosis of F. hepatica.

Ovicidal activity of diaryl dichalcogenides and ivermectin on Fasciola hepatica: A novel candidate for a blending-based therapeutic strategy

Fasciolosis is a food and waterborne disease caused by Fasciola spp., representing a global health burden to various hosts, including humans and other animals. This study investigates the in vitro activity of tellurium- and selenium-containing diaryl dichalcogenides: diacetal ditelluride (LQ07), diacetal diselenide (LQ62), and diacetyl diselenide (LQ68) alone and in combination with ivermectin (IVM) against eggs of Fasciola hepatica. The eggs were exposed for 12 h with each organochalcogen (OC) (0.1 - 2 mmol l-1) and IVM (0.01 - 2 mmol l-1) following an incubation of 15 days, allowing embryonation. The inhibitory concentration of 50 % (IC50) of each OC or IVM was tested with the IC10, IC30, and IC50 of IVM or each OC, respectively. LQ07, LQ62, and LQ68, as well as IVM, demonstrated a concentration-dependent ovicidal activity. The peak ovicidal activity of 99.74 % was achieved when IVM was tested at 2.0 mmol l-1. LQ62 and LQ68 demonstrated greater ovicidal activity, having an IC50 < 0.32 mmol l-1 being 6.25-fold more toxic than IVM alone. The percentage of dead eggs was significantly higher in the IVM group (early mortality), as Se-containing OCs led to the (miracidia) embryonation of the eggs with no hatching (late mortality). Blending Se-containing OCs and IVM showed an additive effect of up to 27 % against F. hepatica eggs. The present data contribute to the potential use of blending-based therapeutic strategies to combat F. hepatica infections in eradication programs worldwide. The combinations may also act against multidrug-resistant strains, reinstating drug-based parasite control.

Advancement in Diagnosis, Treatment, and Vaccines against Fasciola hepatica: A Comprehensive Review

In this review article, we aim to provide an overview of fasciolosis in ruminants. Diagnosis through new coprological methods (such as Flukefinder®, FLOTAC®, and Mini-FLOTAC®) remains the most suitable approach for farms. Regarding treatment, there is a scarcity of available drugs, and resistance to them has prompted new approaches (including drug combinations, enhanced metabolism, or the use of natural compounds) to address this issue. Additionally, several researchers have developed vaccines to control the disease, but their efficacy varies, and none are currently sufficient for commercial use. Further studies are needed to better understand all aspects discussed in this manuscript, with the goal of improving diagnosis, treatment, and disease control. It is important to note that this manuscript does not delve into in-depth knowledge of the discussed aspects; rather, it provides an overview of the different methodologies related to these three aspects of parasitic disease.

One-health approach on the future application of snails: a focus on snail-transmitted parasitic diseases

Snails are fascinating molluscs with unique morphological and physiological adaptive features to cope with various environments. They have traditionally been utilized as food and feed sources in many regions of the world. The future exploitation of alternative nutrient sources, like snails, is likely to increase further. Snails, however, also serve as an intermediate host for several zoonotic parasites. A category of parasitic infections, known as snail-transmitted parasitic diseases (STPDs), is harmful to humans and animals and is mainly driven by various trematodes, cestodes, and nematodes. The environment plays a crucial role in transmitting these parasites, as suitable habitats and conditions can facilitate their growth and proliferation in snails. In light of diverse environmental settings and biologically categorized snail species, this review evaluates the dynamics of significant STPDs of zoological importance. Additionally, possible diagnostic approaches for the prevention of STPDs are highlighted. One-health measures must be considered when employing snails as an alternative food or feed source to ensure the safety of snail-based products and prevent any adverse effects on humans, animals, and the environment.