Thesis (Ph. D. - Microbiology and Immunology)--University of Arizona, 1984. / Includes bibliographical references (leaves 201-208).

Thesis (M.S.)--Ohio University, November, 1989. / Title from PDF t.p.

As the shortage of fresh water becomes more and more critical, alternative sources are being sought. The reuse of wastewater has become a viable option, particularly for agriculture and landscaping. However, the possible presence of the enteric pathogens, especially viruses, in wastewater has created concern about potential health risks associated with this practice. If wastewater is used for irrigation it may contaminate vegetable crops which are commonly eaten raw. Also, it may contaminate grass used for golf courses, school yards, and playgrounds where more people may be exposed. Rotaviruses may be of particular concern since they are a cause of infantile diarrhea and gastroenteritis in adults and have been a cause of waterborne disease outbreaks. No information, however, is available about the dissemination and survival of rotaviruses on uncooked food and landscaped areas. This information is necessary in developing criteria for determining safe uses of wastewater for crop irrigation. A method was developed for recovery of rotavirus from the surface of vegetables. The simian rotavirus SA-11, adsorbed onto the vegetable surfaces and effects of various eluents, pH, and exposure time, was evaluated to optimize recovery. The maximum recovery of rotavirus occurred with a solution of 3% beef extract at pH 8.0 after 5 minutes of exposure. Survival of rotavirus SA-11 on lettuce, radishes, and carrots stored at 4°C and room temperature was evaluated. Rotavirus SA-11 was able to survive up to 30 days at refrigeration temperatures and up to 25 days at room temperatures. Rotavirus survived longest on lettuce. The survival of coliphage and enteric viruses on grass was studied during winter and summer outdoors. Coliphage, poliovirus, and rotavirus SA-11 survived on two types of grass during winter and summer from 8 to 40 hours. Human rotavirus survived longer than the other enteric viruses, however, coliphage was more sensitive to inactivation. The occurrence of rotaviruses and enteroviruses in the secondarily treated sewage (activated sludge) was evaluated over a one year period. Total coliforms, pH, and turbidity were also determined. Rotavirus concentrations peaked during Spring and Winter while concentrations of enteroviruses peaked during May, September, and December. No correlation was found between the concentrations of total coliforms, rotaviruses and enteroviruses.

Thesis (Ph. D. - Microbiology and Immunology)--University of Arizona, 1986. / Includes bibliographical references (leaves 121-126).

Thesis (M.S. - Hydrology and Water Resources Administration)--University of Arizona, 1987. / Includes bibliographical references (leaves 166-176).

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

Ground water has traditionally been considered safe for human consumption without treatment. However, it is an increasingly significant cause of human disease. Although ground water accounts for only approximately 20% of the nation's water supply, over 50% of the waterborne disease outbreaks in the United States are due to the consumption of contaminated ground water. It has been estimated that 65% of the cases of illness in these outbreaks are caused by enteric viruses. Little, however, is known about the persistence of viruses in ground water. The purpose of this study was to try to determine the chemical, physical, and biological factors influencing virus survival in ground water. This information will be helpful in developing criteria for determining safe distances between drinking water wells and sources of potential contamination such as septic tanks and waste application sites. Ground water samples were obtained from eleven sites throughout the United States. In addition, twenty samples were collected from the Tucson basin. The water temperature was measured at the time of collection. Several physical and chemical characteristics (including pH, nitrates, turbidity, and hardness) were determined for each sample. Separate polypropylene tubes containing 50 ml of water were inoculated with each of three viruses: poliovirus-1, echovirus-1 and MS-2 coliphage. Duplicate tubes containing water which had been filtered to remove the indigenous bacteria were also inoculated with viruses. The tubes were incubated at the in situ ground water temperature; selected samples were incubated at two additional temperatures. One-ml subsamples were withdrawn at predetermined intervals over a 30-day period and assayed to determine the number of microorganisms remaining. Multiple regression analysis revealed that temperature was the only water characteristic significantly correlated with the decay rates of all three viruses. Bacteria did not have a consistent effect on the decay rate of the viruses. In addition, no significant differences were found among the decay rates of the three viruses, suggesting that MS-2 coliphage may be able to be used as a model of animal virus behavior in the environment.

Enteric viruses are viruses which replicate in the intestinal tract of man and animals. One mode of transmission for enteric viruses is the fecal-oral route. Drinking water which has been contaminated with sewage or sewage effluent has been implicated as a means for the spread of enteric viruses. Monitoring water for virus contamination requires two steps: 1) the collection and the concentration of the water sample and 2) the isolation and identification of the virus present. Current methods for the detection of enteric viruses in water requires the use of animal cell culture. This technique has several drawbacks, such as: 1) long incubation periods, up to two and three weeks, before some enteric viruses are detected, 2) not all viruses can be detected in one cell line, and 3) not all viruses have been grown in cell culture. More rapid techniques, such as fluorescent antibody or radioimmunoassay do not have the needed sensitivity to detect the low levels of virus found in contaminated water. These techniques also require the production of an antibody for each different virus type. An alternative technique for the detection of viruses in water was sought. Recent advances in recombinant DNA technology now makes it possible to detect viruses without the use of cell culture or antibodies. Gene probes that hybridize to the RNA of poliovirus and hepatitis A virus were tested for their ability to detect different enteric viruses. The probes were labeled with ³²P dCTP and ³²P dATP to a specific activity greater then 1.0 x 10⁹ cpm/ug DNA. Gene Screen Plus (NEN) was chosen as the hybridization membrane since it was more sensitive to virus detection than the other membranes tested. A dot-blot apparatus (Bio Rad) was used to apply the samples. Results were visualized by autoradiography for thirty-six hours at -70° C. One infectious unit of poliovirus and hepatitis A virus was detected using labeled cDNA probes. Upon comparison, the dot blot assay was as sensitive as tissue culture for the detection of poliovirus in beef extract, secondary effluent, and tapwater. Environmental samples, such as secondary effluent, reclaimed wastewater and unchlorinated drinking water were also assayed for poliovirus and hepatitis A virus with the use of gene probes. The results presented here offer an alternative method for screening water samples for the presence of enteric viruses.

Thesis (Ph. D. - Microbiology and Immunology)--University of Arizona, 1989. / Includes bibliographical references (leaves 165-170).

Thesis (Ph. D.)--Michigan State University. Dept. of Crops and Soil Sciences, 2008. / Title from PDF t.p. (viewed Aug. 18, 2009). Includes bibliographical references (p. 147-171). Also issued in print.