Infectious helminth ova in wastewater and sludge: A review on public health issues and current quantification practices

Role of seasonal variation on the prevalence and risk factors of trichuriasis among the aboriginal community in Malaysia

Trichuris trichiura is a soil-transmitted helminth prevalent in developing countries with poor, inadequate sanitation and unsafe water sources. In Malaysia, the prevalence of trichuriasis is relatively high among the aboriginal community due to poverty and poor sanitation. However, there are few studies to determine the seasonal variation on the prevalence and risk factors to acquire Trichuris trichiura infection in Malaysia. The present study found higher Trichuris trichiura infection during the dry season (63.6%; 138/217) in comparison to the wet season (55.5%; 142/256). Low household income, low education level and practice of open defecation were significant risk factors to acquire Trichuris trichiura infection during the wet season. Usage of untreated water supplies for daily activities was a risk factor to acquire trichuriasis during the dry season. This study highlighted that poverty and poor sanitation practices as well as drinking untreated water put the aborigines at high risk to acquire trichuriasis. Therefore, health education, improved sanitation and provision of treated water supply are recommended for the prevention and control of Trichuris trichiura infections in the aboriginal community.

Detection of Helminth Ova in Wastewater Using Recombinase Polymerase Amplification Coupled to Lateral Flow Strips

Ascaris lumbricoides is a major soil-transmitted helminth that is highly infective to humans. The ova of A. lumbricoides are able to survive wastewater treatment, thus making it an indicator organism for effective water treatment and sanitation. Hence, Ascaris ova must be removed from wastewater matrices for the safe use of recycled water. Current microscopic techniques for identification and enumeration of Ascaris ova are laborious and cumbersome. Polymerase chain reaction (PCR)-based techniques are sensitive and specific, however, major constraints lie in having to transport samples to a centralised laboratory, the requirement for sophisticated instrumentation and skilled personnel. To address this issue, a rapid, highly specific, sensitive, and affordable method for the detection of helminth ova was developed utilising recombinase polymerase amplification (RPA) coupled with lateral flow (LF) strips. In this study, Ascaris suum ova were used to demonstrate the potential use of the RPA-LF assay. The method was faster (< 30 min) with optimal temperature at 37 °C and greater sensitivity than PCR-based approaches with detection as low as 2 femtograms of DNA. Furthermore, ova from two different helminth genera were able to be detected as a multiplex assay using a single lateral flow strip, which could significantly reduce the time and the cost of helminth identification. The RPA-LF system represents an accurate, rapid, and cost-effective technology that could replace the existing detection methods, which are technically challenged and not ideal for on-site detection in wastewater treatment plants.

Contamination of wastewater with Echinococcus multilocularis - possible implications for drinking water resources in the QTP China

Echinococcus multilocularis is a parasite that causes a dangerous zoonosis, alveolar echinococcosis (AE). Its presence in water sources, however, has scarcely been studied heretofore. Accordingly, 222 samples of different origin including wastewater from wastewater treatment plants (WWTPs) (n = 137), slaughterhouse (n = 49) as well as water from rivers (n = 26) and a cattle farm (n = 10) were collected from Xining City and a rural area in Qinghai-Tibet Plateau (QTP), an endemic area. Material obtained after processing of 10 L volume samples was subsequently analysed using three molecular detection methods: nested PCR, real-time PCR and LAMP. E. multilocularis DNA was found in 13 (5.85%) water samples; including 8 (5.8%), 3 (6%), 2 (20%) and 0 positive samples found in WWTPs, a slaughterhouse, a cattle farm and rivers, respectively. All three (LAMP, PCR, RT-PCR) molecular tools displayed high agreement and effectiveness in their ability of detecting the parasite's DNA in environmental material. This is the first investigation describing E. multilocularis detection in wastewater samples, using three sensitive molecular diagnostic tools. Results indicate the role of wastewater in dissemination of E. multilocularis and the risk of contamination of water sources.

A Review on the Current Knowledge and Prospects for the Development of Improved Detection Methods for Soil-Transmitted Helminth Ova for the Safe Reuse of Wastewater and Mitigation of Public Health Risks

Climate change, increase in population and scarcity of freshwater have led to a global demand for wastewater reuse in irrigation. However, wastewater has to be treated in order to minimize the presence of pathogens, in particular, the ova of soil-transmitted helminthes (STHs). Limiting the transmission via removal of STH ova, accurate assessment of risks and minimizing the exposure to the public have been recommended by health regulators. The World Health Organization (WHO) guideline specifies a limit of ≤1 ova/L for safe wastewater reuse. Additionally, the Australian Guidelines for Water recycling (AGWR) recommend a hydraulic retention time of over 25 days in a lagoon or stabilization pond to ensure a 4 log reduction value of helminth ova and to mitigate soil-transmitted helminths associated risks to humans. However, the lack of fast and sensitive methods for assessing the concentration of STH ova in wastewater poses a considerable challenge for an accurate risk assessment. Consequently, it has been difficult to control soil-transmitted helminthiasis despite effective mass drug administration. This limitation can be overcome with the advent of novel techniques for the detection of helminth ova. Therefore, this review presents an assessment of the current methods to detect the viable ova of soil-transmitted helminths in wastewater. Furthermore, the review focuses on the perspectives for the emerging state-of-the-art research and developments that have the potential to replace currently available conventional and polymerase chain reaction based methods and achieve the guidelines of the WHO in order to allow the safe reuse of wastewater for non-potable applications, thereby minimizing public health risks.

Detection of helminth ova genera using in-situ biosynthesis of gold nanoparticles

In this study, a presumptive colorimetric method was used to detect and differentiate the ova of two major soil transmitted helminths in wastewater, Ascaris and Trichuris. Gold nanoparticles were synthesised following the reduction of tetrachloroauric acid by the surface moiety of Ascaris suum, resulting in a colour change. In contrast there was no colour change with Trichuris suis indicating the absence of gold nanoparticle synthesis. Analysis of the ova using scanning electron microscopy (SEM) revealed that the synthesis of nanoparticles on the surface of ova was confirmed as gold nanoparticles (91 w/w %) by energy dispersive X-ray analysis (EDX). This study indicated that the surface moieties of helminth ova could be a potential target for ova detection and differentiation using the biosynthesis of nanoparticles by colorimetry methods.

Three advantages:

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Simple colorimetry based method requiring no sophisticated devices.

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No trained personnel required.

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Cost-effective and can be a potential candidate for biosensors.

Removal of helminth eggs by centralized and decentralized wastewater treatment plants in South Africa and Lesotho: health implications for direct and indirect exposure to the effluents

Wastewater may contain contaminants harmful to human health; hence, there is the need for treatment before discharge. Centralized wastewater treatment systems are the favored treatment options globally, but these are not necessarily superior in reduction of pathogens as compared to decentralized wastewater treatment systems (collectively called DEWATS). This study was therefore undertaken to assess the soil-transmitted helminth (STH) and Taenia sp. egg reduction efficiency of selected anaerobic baffled reactors and planted gravel filters compared to centralized wastewater treatment plants in South Africa and Lesotho. The risk of ascariasis with exposure to effluents from the centralized wastewater treatment plants was also assessed using the quantitative microbial risk assessment (QMRA) approach. Eggs of Ascaris spp., hookworm, Trichuris spp., Taenia spp., and Toxocara spp. were commonly detected in the untreated wastewater. The DEWATS plants removed between 95 and 100% of the STH and Taenia sp. eggs, with centralized plants removing between 67 and 100%. Helminth egg concentrations in the final effluents from the centralized wastewater treatment plants were consistently higher than those in the WHO recommended guideline (≤ 1 helminth egg/L) for agricultural use resulting in higher risk of ascariasis. Therefore, in conclusion, DEWATS plants may be more efficient in reducing the concentration of helminth eggs in wastewater, resulting in lower risks of STH infections upon exposure.