Non-travel-related hepatitis E virus (HEV) genotype 3 infections in persons in the Netherlands may have a zoonotic, foodborne, or water-borne origin. Possible reservoirs for HEV transmission by water, food, and animals were studied. HEV genotype 3/open reading frame 2 sequences were detected in 53% of pig farms, 4% of wild boar feces, and 17% of surface water samples. HEV sequences grouped within 4 genotype 3 clusters, of which 1 is so far unique to the Netherlands. The 2 largest clusters contained 35% and 43% of the animal and environmental sequences and 75% and 6%, respectively, of human HEV sequences obtained from a study on Dutch hepatitis E patients. This fi nding suggests that infection risk may be also dependent on transmission routes other than the ones currently studied. Besides the route of exposure, virus characteristics may be an important determinant for HEV disease in humans.H epatitis E virus (HEV) is an RNA virus that causes liver infl ammation in humans, predominantly in developing countries. In the 1990s, serologic studies among blood donors in industrialized countries showed that anti-HEV seropositivity also occurred among a small percentage (1.1%-1.4%) of persons without a travel history to a hepatitis E-endemic region (1,2). Later studies confi rmed sporadic hepatitis E cases contracted in Europe, the United States, and other industrialized regions (3). HEV strains detected in mammals can be classifi ed into 4 major genotypes that are represented by Burmese isolates (genotype 1), Mexican isolates (genotype 2), US isolates (genotype 3), and recent Chinese isolates (genotype 4) (3). In addition, virulent and avirulent HEV strains that infect birds have recently been identifi ed (4,5). In industrialized countries, non-travel-related HEV infections are caused by genotype 3 (Europe, United States, Japan, New Zealand, Argentina) and genotype 4 (Japan, People's Republic of China).A possible role for zoonotic transmission in the epidemiology of human HEV episodes has been suggested after viral RNA was detected in different animal species, and these viruses were found to be closely related to HEV strains found in humans. The fi rst animal in which HEV genotype 3 was identifi ed and characterized was pig in the United States (6). HEV strains of genotypes 3 and 4 have since been detected in pigs in many other countries, and these strains were found to be genetically closely related to HEV strains originating from humans in the same geographic region (7,8). Serologic studies have also indicated a broad host range of HEV. In many animal species such as cows, cats, dogs, rodents, and mongooses, immunoglobulin G to HEV was detected by using several serologic tests. However, HEV RNA was not detected in these animals and because of the lack of positive reference materials to evaluate these tests, the results must be interpreted with caution (9-12).Assuming a zoonotic source for HEV infections, exposure to reservoirs of HEV might occur through contact with infected animals and animal products. Consumption of ...
Concentration of water samples is a prerequisite for the detection of the low virus levels that are present in water and may present a public health hazard. The aim of this study was to develop a rapid, standardized molecular method for the detection of enteroviruses in large-volume surface water samples, using a concentration method suitable for the detection of infectious viruses as well as virus RNA. Concentration of water was achieved by a conventional filter adsorption-elution method and ultrafiltration, resulting in a 10,000-fold concentration of the sample. Isolation of virus RNA by a silica-based RNA extraction method was compared with the nonmagnetic and magnetic NucliSens RNA isolation methods. By using the silica-based RNA extraction method in two out of five samples, enterovirus RNA was detected, whereas four out of five samples were positive following RNA isolation with magnetic silica beads. Moreover, estimated RNA levels increased at least 100 to 500 times. Furthermore, we compared enterovirus detection by an in-house reverse transcription (RT)-PCR with a novel commercially available real-time nucleic acid sequence-based amplification (NASBA) assay. We found that the rapid real-time NASBA assay was slightly less sensitive than our in-house RT-PCR. The advantages, however, of a commercial real-time NASBA assay, like the presence of an internal control RNA, standardization, and enormous decrease in turnaround time, makes it an attractive alternative to RT-PCR.
[1] We investigated transport of viruses through saturated and unsaturated sand columns. Unsaturated experiments were conducted under conditions of uniform saturation and steady state water flow. The water saturation ranged from 1 to 0.5. Bacteriophages MS2 and fX174 were used as surrogates for pathogenic viruses in these studies. Phosphatebuffered solutions with different pH values (7.5, 6.2, 5.5, and 5) were utilized. Virus transport was modeled assuming first-order kinetic adsorption for interactions to the solidwater interface (SWI) and the air-water interface (AWI). Under saturated conditions, virus retention increased as pH decreased, and a one-site kinetic model produced a good fit to the breakthrough curves. Under unsaturated conditions a two-site kinetic model was needed to fit the breakthrough curves satisfactorily. The second site was attributed to the adsorption of phages to the AWI. According to our results, fX174 exhibits a high affinity to the AWI at pH values below 6.6 (the isoelectric point of fX174). Although it is believed that MS2 is more hydrophobic than fX174, MS2 had a lower affinity to the AWI than fX174, presumably because of the lower isoelectric point of MS2, which is equal to 3.9. Under unsaturated conditions, viruses captured within the column could be recovered in the column outflow by resaturating and immediately draining the column. Draining columns under saturated conditions, however, did not result in any recovery of viruses. Therefore the recovery can be attributed to the release of viruses adsorbed to the AWI. Our results suggest that electrostatic interactions of viruses with the AWI are much more important than hydrophobicity.
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