Investigators have linked the outbreak of E. coli bacteria in spinach, which killed three people and sickened more than 200 others across the United States, to wild pigs. The pigs could have spread the bacteria by trampling fences around a spinach field in California.
Samples taken from a wild pig, in addition to stream water and cattle from the ranch, have tested positive for the strain of E. coli implicated in the outbreak.
But investigators have not gone so far as to declare the pigs the source, and are still looking at other possibilities, including runoff, flooding, irrigation water, fertilizer and other wildlife, including deer, as possible sources.
The outbreak appears to be over, and no one has become ill from eating contaminated spinach since September 25.
A guest commentary by Kathryn Price
We have watched the evening news as story after story of incidents related to the E. coli outbreak is told. Many are ill while others die after consuming tainted leafy greens.
What is E. coli? According to the Minnesota Pollution Control Agency, Escherichia coli, a.k.a. E. coli, is "a subgroup of fecal coliform bacteria that is present in the intestinal tracts and feces of warm-blooded animals. It is used as an indicator of the potential presence of pathogens.
There are many different strains of E. coli that are classified into more than 170 serogroups. Although most strains of E. coli are harmless and live in the intestines of healthy humans and animals, the E. coli O157:H7 strain produces a powerful toxin and can cause severe illness."
Here is what is known. According to the San Francisco Chronicle, September 18, 2006, " ... federal authorities announced they will investigate farms in Salinas Valley seeking evidence of what caused the outbreak." 
The article goes on to quote Dr. David Acheson of the FDA saying, "Acheson, who called the outbreak one of the larger E. coli outbreaks ever reported, extended indefinitely the federal recommendation not to eat any fresh spinach or products that contain or are packaged with spinach that have a sell-by date of Aug. 17 through Oct. 1.
The recommendation has brought the spinach harvest to a standstill in the Salinas Valley, according to Joe Pezzini, chairman of the Central California Grower-Shipper Association and vice president of operations at Ocean Mist Farms in Castroville. Ocean Mist doesn't supply spinach to Natural Selection Foods, one of the first producers tied to the outbreak, but Pezzini said the government warning affected all growers?.
Acheson said all the farms that agents will visit today in connection with the outbreak are in the Salinas Valley, which produces much of the nation's lettuce and spinach. Authorities are continuing to investigate whether other companies and brands are involved."
Pecarich, a retired Soil Scientist in Ventura, California writes Monterey County, California "implemented what is called the Castroville Seawater Intrusion Project which, in short, mixes 66% tertiary level treated sewage effluent with 33% potable water. This was done under the auspices of the Monterey County Water Resource Agency and cost $78 million.
In brief, this project supplies 13,000 acre/feet of treated sewage effluent wastewater annually to approximately 12, 000 acres of cropland through 46 miles of pipeline to irrigate agricultural fields overlying the seawater intruded aquifer. The crops that are irrigated include spinach and lettuce." 
According to the Food and Agriculture Organization of the United Nations (FAO), the "Monterey Wastewater Reclamation Study for Agriculture (MWRSA) was a 10-year, US $7.2 million field-scale project designed to evaluate the safety and feasibility of irrigating food crops (many eaten raw) with reclaimed municipal wastewater (Sheikh et al. 1990).
Demonstration fields at Castroville in the lower Salinas Valley, California were used to study full-scale farm practices using reclaimed municipal wastewater. Two 5-hectare experimental plots provided large amounts of data on crop response which were subjected to statistical analysis. On one plot artichokes were grown, while on the other a succession of broccoli, cauliflower, lettuce and celery was raised over a 5-year period starting in late 1980." 
Here are a few definitions to learn:
Potable Water: Water that is safe for human consumption.
Municipal Wastewater: Discharge of effluent from wastewater treatment plants which receive wastewater from households, commercial establishments, and industries. Combined sewer/separate storm overflows are included in this category.
Effluent: Liquid waste, often from a factory or sewer. This is a term that is often used to refer to the urine and manure that is pumped into or out of a lagoon.
Reclaimed Water: Wastewater (sewage) that has been treated and purified for reuse, rather than discharged into a body of water. It is frequently used to irrigate golf courses and parks, fill decorative fountains, and fight fires. It can also be used to irrigate crops, as long as they will be peeled or boiled before human consumption.
Pathogenic: Capable of causing disease; harmful; any disease-causing agent.
According to the last definition, food irrigated with reclaimed water should not be eaten raw. It appears the U.S. citizen is the laboratory rat.
In January 2002, the Carlsbad Municipal Water District was quoted as saying, "One of the wisest uses of water is to give it a second chance to use it again after it is flushed down the drain at our homes and businesses. This process is called recycling wastewater, or water recycling. It's a lot like cleaning and reusing your clothes when they get dirty." 
Carlsbad Municipal Water District is wrong. It is nothing like cleaning and reusing your clothes since your clothing does not usually have urine, feces, oil, gas, road kill and other contaminants found on them. Also, we do not ingest our clothing as we do the produce irrigated with recycled wastewater opening the door for plant tissue to harbor harmful, and potentially lethal, organisms.
Why would we use potentially harmful methods of irrigation for our nation's food supply? According to the USDA, Agricultural Research Service's (ARS) Research Project: Groundwater Recharge and Wastewater Irrigation to Protect Crops and Groundwater, a 2005 Annual Report, it is stated that:
"Water demands in the western US currently exceed available supplies. Population growth and water shortages will increase the need to use treated wastewater effluent for irrigation, particularly in areas where fresh water resources are limited. The use of recycled water for municipal and crop irrigation will reduce groundwater pumping, which currently provides 37% of water for agricultural use and is the largest user of groundwater nationwide." 
Perhaps population explosions in the west are a direct result of the current illegal alien issue; another topic for another time. Nevertheless, this problem could be corrected if so desired by the powers that be.
Who are the most vulnerable of getting E. coli? According to the EPA website, "Children under the age of five, the elderly, and people whose health is weakened (i.e., people who have long-term illnesses such as cancer or AIDS) are at greater risk of severe illness." 
The most shocking realization during the gathering of information regarding this topic is how much the USDA understood was at risk. The USDA ARS 2005 Annual Report goes on to say, "Using present technologies, municipal wastewater treatment may not completely disinfect recycled irrigation waters, allowing pathogenic microbial populations to re-grow in water storage and transmission systems.
As a result, recycled water used for agricultural and municipal irrigation can contain enough pathogenic organisms to threaten human health once released into the environment. Moreover, little is known about the long-term environmental fate of synthetic organic compounds, including pharmaceutically active chemicals and disinfection byproducts, contained in recycled wastewater. Overall, the environmental and public health impacts of irrigation with reclaimed sewage effluent and the potential degradation of underlying groundwater are largely unknown."
Some of the USDA ARS objectives found in the same report include:
Objective 1: Develop methods for improved environmental detection of contaminants and pathogens using field studies in areas with a history of wastewater application.
Objective 2: Determine the environmental fate and transport of contaminants and pathogens using focused studies in agricultural fields, municipal irrigated areas (golf courses, parks), and/or groundwater recharge areas with a long history of municipal wastewater application.
Objective 3: Examine novel methods to control bacterial growth and chemical transport in conveyance systems using laboratory reactor studies, to aid in development of management strategies to minimize environmental impacts of using treated effluent for irrigation.
This research directly addresses the national and global problem of food safety in agricultural areas that have been irrigated with sewage effluent or with effluent contaminated water. The research also addresses issues of water conservation and integrated water management through water reuse.
These issues now occur or are emerging in many parts of the US and the rest of the world wherever there is insufficient water to meet competing demands for municipal, industrial, and agricultural irrigation. All objectives fall under National Program 201, Water Quality and Management.
By addressing water conservation and integrated water management through water reuse, Objectives 1 and 2 fall under Problem Area 2.5 (Waste Water Reuse), Goal 2.5.3 (Waste Water Standards). Objective 3 addresses Problem Area 2.3 (Water Conservation Management), Goal 2.3.1 (Water Conservation Technologies)."
The most damning evidence against the USDA ARS is their admittance of possible harmful effects of using recycled wastewater to irrigate our produce.
Section 5 of the report says, "Microbiological work in the earlier projects included a laboratory study to assess the survival and re-growth potential of bacteria present in tertiary-treated effluent as it passed through a model distribution system. The results demonstrated that population numbers of indicator bacterial organisms increased by three to four orders of magnitude over the 11-day length of the experiment.
This research established that although the reclaimed water met EPA standards for irrigation at the treatment plant, there is great potential for bacterial re-growth during transport that could place the water out of compliance at the point of intended use.
This work illustrated the critical need to understand the environmental fate of microorganisms and the potential for bacterial re-growth in reclaimed water used for crop irrigation so that future problems of food and groundwater contamination via wastewater irrigation can be prevented."
It appears the USDA does not know what the long term effects will be using recycled wastewater on crops or humans who consume their harvests making all of us who shop in our local grocery store their guinea pig.
Armed with the knowledge above, is it possible the tainted flesh of California produce in the Salinas Valley is a result of the poor decision to use recycled wastewater effluent to irrigate the nation's food supply? I will be thinking twice before serving my children leafy greens grown in California. Be sure to check your own community's irrigation practices before believing your locally grown produce is any safer.
 San Francisco Chronicle, Spinach probe of Salinas Valley
Feds tracking cause of E. coli outbreak http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/09/18/MNGRBL7IQ71.DTL
 California Progress Reporthttp://www.californiaprogressreport.com/ and http://www.bapd.org/n7652.html
 FAO Corporate Document Repository http://www.fao.org/docrep/T0551E/t0551e0b.htm
 EcoISP, California Drinking Water Protected by Wastewater Recycling http://www.ecoisp.com/resources6.asp
 USDA Agricultural Research Service, Groundwater Recharge and Wastewater Irrigation to Protect Crops and Groundwater http://www.ars.usda.gov/research/projects/projects.htm?ACCN_NO=408631&showpars=true&fy=2005
 US Environmental Protection Agency, E. coli 0157:H7 in drinking water -- US EPA http://www.epa.gov/safewater/ecoli.html