Cause Of Waterborne Disease Research Articles

Viral contamination of food products: a poorly understood public health problem

Throughout the world there have been several epidemics of food-borne diseases (FBD) about which there is lack of sufficient information for public health institutions to take appropriate measures. This study was conducted for the purpose of contributing to the dissemination of information on these diseases and their etiologic agents, epidemiology, and control. The study was based on data from 61 sources, including review articles, reports of outbreaks, and databases. Results reveal considerable underregistration and lack of data on FBD throughout the various countries, with viruses being the second most important cause of FBD in the United States of America. Two agents, Norwalk virus and hepatitis A virus, were the fifth and sixth most frequent causes, respectively, although the former was the single most frequent cause of FBD in 1982 and the second most frequent cause of water-borne diseases during the period from 1986 to 1988. Despite the scarcity of information on the problem, rotavirus, poliovirus, hepatitis E virus, astrovirus, and small gastroenteric viruses are also important causes of FBD. We also discuss the importance of viral zoonoses, especially hemorrhagic fevers transmitted by contact with rodent feces and tick-borne viral encephalitides (Lassa fever). There is discussion of the controversial mad cow disease and its potential transmission through food products, as well as of dietary aspects of the management of AIDS and other viral infections. Finally, measures for the prevention and control of FBD are described.

The Emerging Recognition of Cryptosporidium as a Health Hazard

Cryptosporidium is the leading cause of waterborne disease in the United States. Cryptosporidiosis occurs as a result of this pathogen and is potentially fatal to the immunosuppressed population. Current water treatment standards will not eradicate the pathogen, resulting in a potential public health hazard. Congress recently passed legislation addressing cryptosporidium, and health policies are pending approval with strong support from the Centers for Disease Control. The implication for community health nursing is that nurses should take on expanded roles as social, political, and economic advocates and educators to support community actions to eradicate this pathogen.

Application of flow cytometric methods for the routine detection of Cryptosporidium and Giardia in water.

Cryptosporidium and Giardia are common causes of waterborne disease. The currently used methods of detecting these organisms in water rely on filtration capture, immunofluorescence labelling, and epifluorescence microscopy. These methods are inefficient, labour intensive, and require a highly skilled microscopist. We describe an alternative technique using flocculation concentration, followed by flow cytometry with fluorescence activated cell sorting. Environmental samples were analysed, and protozoan-like particles were sorted and collected before confirmation with epifluorescence microscopy. The technique was found to be significantly more sensitive and considerably faster than the conventional methods.

Virus Survival and Transport in Ground Water

Viruses are a significant cause of waterborne disease in the United States; it has been estimated that they may be responsible for as much as 50% of the reported outbreaks. This fact has led the U.S. Environmental Protection Agency to propose a maximum contaminant level goal (MCLG) for viruses in drinking water. Septic tanks, which contribute over one trillion gallons of waste to the subsurface every year, are a major source of viruses in soils and ground water. The purpose of this research was to develop a model which could be used to estimate safe distances between septic tanks, or other sources of contamination, and drinking-water wells. The model was based on ground-water flow characteristics and the length of time that viruses remain infective in the subsurface environment. Water samples were collected from 71 continuously pumping municipal drinking-water wells. Viruses were inoculated into the water samples, and the rate at which the viruses were inactivated was calculated for each sample. The inactivation rates were determined to be spatially correlated by calculating a semivariogram. Kriging, a geostatistical technique, was used to estimate virus inactivation rates at unsampled locations using the measured values at nearby locations. The measured and kriged virus inactivation rates were used in conjunction with the regional ground-water flow characteristics to calculate septic tank setback distances over a city-wide area. The setback distance was defined as the distance required for a 7-log reduction in virus number in the time that the water traveled from the source of contamination to a drinking-water well. The model has been extended to account for alterations in the flow field caused by the presence of pumping wells. Setback distances of less than 15 m to greater than 300 m have been calculated using these models. The results of this research may be useful for community planning purposes, because areas with higher potentials for viral contamination of ground water may be identified based on the maps generated by the model. In addition, the models may be useful in granting variances from the mandatory ground-water disinfection requirement under consideration by the Environmental Protection Agency.