Survival of enteric viruses under natural conditions in a subarctic river

Waterborne norovirus outbreaks

Noroviruses (NoVs) are the most common nonbacterial causative agents of waterborne outbreaks. Due to the mild and short-lived disease of gastroenteritis, even large epidemics may go unnoticed, since patients do not necessarily visit a doctor. NoVs have several means by which to survive both in the environment and in a population. The nonenveloped small virus retains its infectivity in the environment, and particularly in cold water, for a long time. Unlike most enteric viruses, it causes disease both in children and adults. A large number of genotypes combined with a small infective dose and short-term immunity guarantee efficient circulation of these viruses. The world of NoVs has been revealed to us predominantly by molecular methods. Having learned to detect these viruses first in patients, the emphasis is now in searching for methods sensitive enough to find them in environmental samples. In this review, the latest methods and their use in monitoring of these viruses are discussed.

Waterborne outbreak of viral gastroenteritis

A waterborne epidemic took place in a Finnish municipality in April 1994. Some 1500-3000 people, i.e. 25-50% of the population, had symptomatic acute gastroenteritis. Laboratory findings confirmed adenovirus, a Norwalk-like agent, small round viruses (SRV), and group A and C rotaviruses as causative agents, Norwalk virus being the main cause of the outbreak. The epidemic was most probably associated with contaminated drinking water. The groundwater well, situated in the embankment of a river, was contaminated by polluted river water during the spring flood. A back flow from the river to the well had occurred via a forgotten drainage pipe.

Seasonal distribution of adenoviruses, enteroviruses and reoviruses in urban river water

In the 63-month period from January 1988 to March 1993, monthly levels of adenoviruses, enteroviruses (coxsackie B, polio, echo) and reoviruses in the urban river water in Nara Prefecture, Japan were in the range 0-25, 0-190 and 0-325, plaque forming units per liter (PFU/liter), and the average levels were 2.4, 40.6 and 56.2 PFU/liter, respectively. The peak reovirus level was found in winter during the cold weather months (Nov. to Mar.). The peak enterovirus level was found in summer (May to Sept.) but continued to be found in autumn-winter (Oct. to Jan.) from 1991 to 1993. The levels of adenoviruses were low throughout all 5 years, as compared to those of reoviruses and enteroviruses. Polioviruses were isolated following the administration of vaccine. Although a changing pattern of serotype prevalence was seen with the coxsackie B viruses and echoviruses from 1988 to 1993, this is not so for polioviruses, which remained almost unchanged for the five-year period. Adenoviruses were isolated throughout all five years, though in small numbers. Reoviruses were isolated most frequently throughout five years.

Enteroviruses in recreational waters of Northern Ireland

Virus surveillance of Northern Ireland recreational waters, between April 1986 and May 1989 demonstrated widespread enteroviral contamination of coastal and inland waters. In 1986, enteroviruses were detected in 4 of 46 (8.7%) water samples, collected from 6 coastal bathing waters. In 1987, 49 of 107 (45.8%) samples, from 16 coastal bathing waters, yielded enteroviruses; 33 of the enterovirus positive samples passed one or both of the coliform standards outlined by the European Economic Community (EEC) bathing water directive (76/160/EEC). Enteroviruses were also detected in 33 of 39 (84.6%) samples tested from 3 inland recreational waters.

Animal viruses, coliphages, and bacteria in aerosols and wastewater at a spray irrigation site

Aerosol samples collected at the Muskegon County Wastewater Management System Number 1 spray irrigation site in Michigan by using the Army prototype XM2 Biological Sampler/Collector were examined for the presence of animal viruses, coliphages, and bacteria. Air samples, collected in Earle lactalbumen hydrolysate, and wastewater samples were filtered through a 0.45- and 1.2-micron membrane filter sandwich, pretreated with 10% beef extract (pH 7.0), and assayed for animal viruses by the plaque method on Buffalo green monkey kidney cells. Untreated air and wastewater samples were assayed for coliphages by the soft agar overlay method with three Escherichia coli hosts (ATCC 13706, 15597, and 11303) and for bacteria by the heterotrophic plate count method. Filtered air samples were assayed for coliphages by the most-probable-number method with the same three hosts. Although no animal viruses were detected in the aerosol samples, coliphages and bacteria were recovered. E. coli ATCC 13706 coliphage were recovered more often and in greater numbers than either of the other two types of coliphages. Concentrations of animal viruses, coliphages, and bacteria detected in the raw influent decreased as the wastewater was aerated and stored in the lagoons. No animal viruses were detected in the wastewater at the pump station just before distribution to the spray irrigation rigs. The most-probable-number method was more sensitive and consistent than the overlay procedure in detecting low levels of coliphages in air samples.

Recovery of viruses from water by a modified flocculation procedure for second-step concentration

A reduction in virus recovery efficiencies stemming from a change in the commercial processing of powdered beef extract was reversed by the addition of Celite analytical filter aid. Supplementing beef extract with this silicate is recommended as a modification to the organic flocculation procedure for second-step concentration in monitoring for waterborne viruses. Considerable differences in virus recovery were found among lots of beef extract and Celite preparations; this indicates that the performance of each lot of these substances should be checked before use.

Optimization of the BGM cell line culture and viral assay procedures for monitoring viruses in the environment

An in-depth study of the continuous cell line designated BGM is described herein, and recommendations are made for standardizing cell culture and viral assay procedures. Based on data gathered from a survey of 58 laboratories using this cell line, a research plan was developed that included the study of growth media, sera, NaHCO3 levels, culture bottles, cell concentration, overlay media, agar, virus infection conditions, and cell-dissociating agents. Additionally, a comparative virus isolation study with BGM cells and nine other cell types was conducted with 37 sewage samples collected from nine different geographic areas. The results of the study indicated that the BGM cell line is superior for virus isolation when compared with the other cell types and that certain media and additives tend to increase BGM cell sensitivity to a specific group of viruses. A standardized procedure for cultivation of BGM cells is described which provides a more effective enterovirus assay system.

Indicator organisms for estuarine and marine waters

The use of indicator organisms for estuarine and coastal waters has been reviewed. The natural flora of the environment must be considered in selecting an indicator organism, but, more importantly, recent work which shows a viable but non-recoverable stage of pathogens entering the marine environment demonstrates that the conventional detection of indicator microorganisms is misleading, if not inaccurate. Results suggest that the newly developed epifluorescent/immunofluorescent direct detection of pathogens in the environment may be the most reliable method for determining public health hazards in marine and estuarine waters.

Indicator organisms for estuarine and marine waters

Abstract The use of indicator organisms for estuarine and coastal waters has been reviewed. The natural flora of the environment must be considered in selecting an indicator organism, but, more importantly, recent work which shows a viable but non‐recoverable stage of pathogens entering the marine environment demonstrates that the conventional detection of indicator microorganisms is misleading, if not inaccurate. Results suggest that the newly developed epifluorescent/immunofluorescent direct detection of pathogens in the environment may be the most reliable method for determining public health hazards in marine and estuarine waters.

Processing and transport of environmental virus samples

Poliovirus-seeded tap water, conditioned with MgCl2 and passed through virus-adsorbing filters, gave better poliovirus recovery than water identically treated but conditioned with AlCl3. Elution of several filter types with beef extract yielded higher recoveries than did elution with glycine. Seeded samples filtered through various filters and stored showed considerable virus loss in 2 days when stored at 4 degrees C, whereas those stored at -70 degrees C gave stable virus recovery up to 4 days. Additionally, the use of antifoam during the elution process reduced foaming and increased virus recovery by 28%.

Adsorption of reovirus to clay minerals: effects of cation-exchange capacity, cation saturation, and surface area

The adsorption of reovirus to clay minerals has been reported by several investigators, but the mechanisms defining this association have been studied only minimally. The purpose of this investigation was to elucidate the mechanisms involved with this interaction. More reovirus type 3 was adsorbed, in both distilled and synthetic estuarine water, by low concentrations of montmorillonite than by comparable concentrations of kaolinite containing a mixed complement of cations on the exchange complex. Adsorption to the clays was essentially immediate and was correlated with the cation-exchange capacity of the clays, indicating that adsorption was primarily to negatively charged sites on the clays. Adsorption was greater with low concentrations of clays in estuarine water than in distilled water, as the higher ionic strength of the estuarine water reduced the electrokinetic potential of both clay and virus particles. The addition of cations (as chloride salts) to distilled water enhanced adsorption, with divalent cations being more effective than monovalent cations and 10(-2) M resulting in more adsorption than 10(-3) M. Potassium ions suppressed reovirus adsorption to montmorillonite, probably by collapsing the clay lattices and preventing the expression of the interlayer-derived cation-exchange capacity. More virus was adsorbed by montmorillonite made homoionic to various mono-, di-, and trivalent cations (except by montmorillonite homoionic to potassium) than by comparable concentrations of kaolinite homoionic to the same cations. The sequence of the amount of adsorption to homoionic montmorillonite was Al greater than Ca greater than Mg greater than Na greater than K; the sequence of adsorption to kaolinite was Na greater than Al greater than Ca greater than Mg greater than K. The constant partition-type adsorption isotherms obtained when the clay concentration was maintained constant and the virus concentration was varied indicated that a fixed proportion of the added virus population was adsorbed, regardless of the concentration of infectious particles. A heterogeneity within the reovirus population was indicated.

A method for recovering viruses from sludges

Primary, activated, and anaerobic mesophilically digested sludges were salted with MgCl2 (divalent cations) or AlCl3 (trivalent cations) and acidified to bind indigenous unadsorbed virions to the sludge solids; the sludges were centrifuged, and the adsorbed virions were eluted from the solids with buffered 10% beef extract. The elution yields with this procedure were superior to those obtained from sludges that had been salted or acidified only. Homogenization of sludges prior to other treatment did not increase the numbers of virions recovered.

Coliphages as ecological indicators of enteroviruses in various water systems

The occurrence of coliphages and enteroviruses in a variety of water systems in Czechoslovakia was monitored for two years. Two host strains of Escherichia coli bacteria were used to test 1161 water samples for the presence of bacteriophages. These strains were polyvalent hosts for a broad spectrum of morphologically distinct coliphages, and their use thus gave quantitative data on the degree of viral pollution in any given water sample. Ninety-two water samples were tested in parallel for the presence of enteroviruses, by using a flocculation method to concentrate the viruses followed by isolation in cultures of a buffalo green monkey (BGM) kidney continuous cell line. The enterovirus and coliphage recovery rates showed similar differences when waters with different levels of pollution were compared. Seasonal fluctuations of both the coliphage and enterovirus (mostly poliovirus) levels in river water were demonstrated by statistical analysis of the data collected. The levels increased in the winter and sharply declined in the summer months as the river water temperature increased. Chemical pollution did not seem to influence the survival of either the coliphages or the enteroviruses in the observed rivers.