Detection of small round structured viruses in artificially contaminated water using filter adsorption and reverse transcription polymerase chain reaction

Evaluation of virus recovery methods and efficiency of tannin-derived coagulants in removing total coliforms, E. coli and enteric viruses in effluents of a domestic sewage treatment plant

In the present study, nine coagulants having potential to be used for sewage treatment were compared to assess their efficiency in removing total coliform bacteria, Escherichia coli and adenovirus. The coagulants tested were metallic and organic and their efficiency was compared when treating samples of raw and treated sewage (activated sludge). Before the efficiency tests of the coagulants, viral concentration methods were compared. Coagulation tests were carried out by using the jar-test system and the doses used ranged from 100 ppm to 1,000 ppm. Viral DNA was extracted and subjected to real-time polymerase chain reaction (qPCR) using primers for the gene of AdV hexon. Aluminum sulfate (1,000 ppm) presented the best results for raw sewage among metal coagulants whereas Acquapol^® C118 and WW (1,000 ppm) had the most satisfactory results among organic coagulants, both reducing up to 7 logs for coliforms and 4 logs for virus. For the treated effluent, FeCl₂ (1,000 ppm) presented best results for metal coagulants, whereas, from organic coagulants, the best removal rates were for Acquapol^® 893/11 (1,000 ppm), both reducing up to 3 logs for coliforms and 4 logs for virus.

Concentration and recovery of viruses from water: a comprehensive review

Enteric viruses are a cause of waterborne disease worldwide, and low numbers in drinking water can present a significant risk of infection. Because the numbers are often quite low, large volumes (100-1,000 L) of water are usually processed. The VIRADEL method using microporous filters is most commonly used today for this purpose. Negatively charged filters require the addition of multivalent salts and acidification of the water sample to effect virus adsorption, which can make large-volume sampling difficult. Positively charged filters require no preconditioning of samples, and are able to concentrate viruses from water over a greater pH range than electronegative filters. The most widely used electropositive filter is the Virosorb 1MDS; however, the Environmental Protection Agency has added the positively charged NanoCeram filters to their proposed Method 1615. Ultrafilters concentrate viruses based on size exclusion rather than electrokinetics, but are impractical for field sampling or processing of turbid water. Elution (recovery) of viruses from filters following concentration is performed with organic (e.g., beef extract) or inorganic solutions (e.g., sodium polyphosphates). Eluates are then reconcentrated to decrease the sample volume to enhance detection methods (e.g., cell culture infectivity assays and molecular detection techniques). While the majority of available filters have demonstrated high virus retention efficiencies, the methods to elute and reconcentrate viruses have met with varying degrees of success due to the biological variability of viruses present in water.

New electropositive filter for concentrating enteroviruses and noroviruses from large volumes of water

The U.S. Environmental Protection Agency's information collection rule requires the use of 1MDS electropositive filters for concentrating enteric viruses from water, but unfortunately, these filters are not cost-effective for routine viral monitoring. In this study, an inexpensive electropositive cartridge filter, the NanoCeram filter, was evaluated for its ability to concentrate enteroviruses and noroviruses from large volumes of water. Seeded viruses were concentrated using the adsorption-elution procedure. The mean percent retention of seeded polioviruses by NanoCeram filters was 84%. To optimize the elution procedure, six protocols, each comprising two successive elutions with various lengths of filter immersion, were evaluated. The highest virus recovery (77%) was obtained by immersing the filters in beef extract for 1 minute during the first elution and for 15 min during the second elution. The recovery efficiencies of poliovirus, coxsackievirus B5, and echovirus 7 from 100-liter samples of seeded tap water were 54%, 27%, and 32%, respectively. There was no significant difference in virus recovery from tap water with a pH range of 6 to 9.5 and a water flow rate range of 5.5 liters/min to 20 liters/min. Finally, poliovirus and Norwalk virus recoveries by NanoCeram filters were compared to those by 1MDS filters, using tap water and Ohio River water. Poliovirus and Norwalk virus recoveries by NanoCeram filters from tap and river water were similar to or higher than those by the 1MDS filters. These data suggest that NanoCeram filters can be used as an inexpensive alternative to 1MDS filters for routine viral monitoring of water.

Adenovirus detection in shellfish and urban sewage in Morocco (Casablanca region) by the polymerase chain reaction

Human enteric viruses are largely excreted in faeces. These resistance of these viruses in the environment makes their faecal-oral transmission easier. Filter feeder organisms such as the mussels are bio-accumulators of viruses contaminating their aquatic environment. Thus, undercooked shellfish consumption involves sanitary risks. Thirty samples of mussels (Mytilus sp.), were tested, half were from an aquaculture origin, the others were from an area more exposed to faecal pollution. Fifteen sewage samples from this last area were also examined. Viruses were extracted from the digestive tissue by direct elution method in a glycine/NaCl pH 9.5 buffer followed by PEG 8000 precipitation. The PEG pellets were used for DNA extraction by proteinase K and phenol/chloroform. The molecular characterization, by PCR using specific adenovirus primers revealed that shellfish growing on Mohammedia (a town in the Casablanca outskirts) littoral are contaminated whereas those chosen from aquaculture and bought in the central market were not contaminated.

"Norwalk-like viruses" as a cause of foodborne disease outbreaks

While outbreaks of foodborne disease remain an important public health concern, their aetiology is not identified in a majority of instances. In targeted studies, the application of newly developed molecular assays has demonstrated that a large proportion of these outbreaks may be caused by the "Norwalk-like viruses" (NLV), a genus of genetically related viruses belonging to the family Caliciviridae. NLV outbreaks associated with consumption of faecally contaminated oysters are frequently reported and can best be controlled by preventing contamination of oyster-harvesting waters. Infectious foodhandlers are another frequent source of contamination, and such transmission can be minimised by exclusion of ill foodhandlers and the maintenance of strict personal hygiene. Molecular assays have greatly refined the epidemiological investigation of foodborne NLV outbreaks, allowing the linking of outbreaks in different locations and permitting the identification of the virus in the implicated vehicle. The development of simpler and more sensitive assays and their use on a broader scale will assist in defining the true burden of foodborne NLV outbreaks and improve strategies for their prevention and control.

Immunomagnetic separation of a Norwalk-like virus (genogroup I) in artificially contaminated environmental water samples

Rabbit polyclonal antibodies were raised against a recombinant capsid protein from a genogroup I Norwalk-like virus (NLV). Magnetic beads coated with these antibodies were used in immunomagnetic separation (IMS) of the NLV. After capture of the NLV and washing of the beads, viral RNA was heat released and detected by RT-PCR. This IMS procedure was shown to have high sensitivity for detection of homologous NLV, while capture of a genogroup II NLV was less efficient. Antigen capture was not influenced by the content of humic acids in the samples. The combination of IMS and heat release was found to be more efficient than organic extraction of RNA from water contaminated with humic acids. The efficacy and simplicity of IMS/heat release render this combination a feasible tool for the preparation of NLV RNA from environmental samples, although the antigenic diversity of NLV may be a complicating factor.