May 2007, Vol. 19, No.5
Avian Flu Virus Unlikely To Spread Through Wastewater, Drinking Water Systems
A close relative of the highly pathogenic avian influenza virus (H5N1) can be eliminated by wastewater and drinking water treatments, including chlorination, ultraviolet (UV) radiation, and bacterial digestion, according to a Cornell University (Ithaca, N.Y.) news release. The virus is harmless to humans but provides a case study of the pathways by which the influenza could spread to human populations.
Cornell researchers studied the related virus, called H5N2, to see whether a hypothetical mutated form of H5N1 could infect people through drinking and wastewater systems. Researchers at Cornell and the U.S. Military Academy at West Point (N.Y.) collaborated on the study, published in a recent issue of Environmental Engineering Science.
H5N2, a low-pathogenic avian influenza virus that is not contagious for humans, is physically similar to H5N1, which since 2003 has been lethal to millions of birds globally and more than half of the almost 200 infected people, mostly through handling infected birds. Researchers and officials are concerned that if H5N1 mutates to transmit easily between people, a deadly global pandemic could occur.
“It is unknown if H5N1 is more resistant” than H5N2 to procedures used by the water management industry, said Araceli Lucio–Forster, the paper’s lead author and a teaching support specialist in Cornell’s Department of Microbiology and Immunology. Because H5N1 requires high-level biosafety facilities, Lucio–Forster and colleagues used H5N2 as a surrogate virus. Given the similarities between the two viruses, Lucio–Forster said she thinks that if H5N1 entered the water treatment system, “the virus should be inactivated, which means treated water may not be a likely source of transmission.”
Overall, avian flu viruses do not survive well outside of a host. Still, the researchers tried to address concerns in the wastewater treatment industry that if a human outbreak occurred, contaminated feces passing through the plant could infect plant workers and spread elsewhere through drinking water.
“You have some 50,000 treatment plants in the U.S., and all these operators that run the plants were concerned that if there were an influenza outbreak and everyone were sick, is it going to come into the plant and infect them and others,” said co-author Dwight Bowman, a professor of parasitology at Cornell.
To test the effectiveness of UV radiation for killing the H5N2 virus, the researchers exposed the virus in drinking water, as well as in wastewater effluents, to UV light at varying levels. The treatment was effective in killing H5N2 at levels well within industry standards (and at lower levels than are used for killing Cryptosporidium and Giardia in water).
For chlorine, which is mostly ubiquitous in U.S. drinking water, the results were less definitive. Inactivation of H5N2 depends on both chlorine concentrations and time of exposure. On average, U.S. treatment plants treat drinking water with chlorine concentrations of 1 mg/L for 237 minutes. Under these conditions, the researchers found that H5N2, and probably H5N1, would be mostly inactivated, but further studies are needed to see if the viruses stay active when they come out of feces or are at different pH and salinity levels.
Similarly, the small laboratory-scale study found that bacterial digesters also reduced H5N2 to undetectable levels after 72 hours, which is consistent with industry standards. The researchers also found that higher digester temperatures inactivated the virus more quickly.
For more on Cornell’s ongoing avian flu research, see www.news.cornell.edu/Chronicle/features/avian_flu/avian_flu.shtml.
Scientists Help Agriculture Face a Future With Less Water
Farms in the semiarid western United States produce a large portion of the nation’s food and fiber, most with irrigation. Yet, as available water supplies shrink and competing demands for water increase, western agriculture faces an uncertain future, according to scientists from Oregon State University (OSU; Corvallis).
Scientists from around the world convened in February to discuss the water crisis in agriculture and explore how new research can help farmers produce more with less, according to an OSU news release. Their discussion was part of the annual meeting of the American Association for the Advancement of Science (Washington, D.C.), held in San Francisco.
“There is no question that the greatest challenge for agriculture in the near future will be the availability of adequate supplies of water of sufficient quality to support agricultural production,” said Stella M. Coakley, an associate dean of the College of Agricultural Sciences at OSU and one of the panel organizers.
Coakley, a plant pathologist with a specialty in climatic effects, sees the issues of water security and food security converging in agricultural areas around the world, including many parts of Oregon.
Panel members described how an increase in population, urbanization, and environmental consciousness has increased various demands for water, outbidding and reducing the water available for agriculture. Shrinkage of groundwater resources and a prolonged drought have aggravated the situation, according to the OSU news release, and the greater frequency of more severe droughts predicted by some global climate change models are a cause for great concern.
In addition, global warming appears to be increasing the water requirements of plants. There was much talk of potential water security advancements and issues in the western United States.
Ray Huffaker, from the School of Economic Sciences at Washington State University (Pullman), addressed the changes needed in federal water laws and policies to protect water rights and to enhance efficiencies in water distribution, allocation, and marketing. Bert Clemmens, from the Arid Land Agricultural Research Center (Maricopa, Ariz.), discussed actions and technologies that could reduce field losses of rain and irrigation waters. Robert Evans, from the U.S. Department of Agriculture’s Agricultural Research Service in Sidney, Mont., described how competition for water soon will require a major shift from maximizing agricultural productivity per unit of land to maximizing productivity per unit of water consumed. He outlined new methods to increase water use efficiency of crops, technologies that include site-specific water management.
John Letey, a professor emeritus of soil and water sciences at the University of California, Riverside, spoke of his work modeling soil salinity and reuse of saline and other impaired waters.
“These are some examples of what we might do to address the water security in the West,” Coakley said.
Contact Coakley at (541) 737-5264.
Pinpointing Contamination Sources
An Oregon State University (OSU; Corvallis) microbiologist has developed a molecular test to determine the source of fecal contamination in water, according to an OSU news release.
This type of detection, called “fecal source tracking,” is both faster and far more specific than traditional standard fecal coliform tests, according to Katharine G. Field, who developed the test. Results of a Tillamook Bay (Ore.) study using the new methodology were published in a recent issue of Applied and Environmental Microbiology.
Field and her colleagues found a way to use gene amplification to determine the kind of fecal bacteria in polluted water and its source, according to OSU. Their new technique detects the presence of markers — unique gene sequences from specific strains of bacteria — found in host species, such as humans and cows.
Until a few years ago, it was impossible to pinpoint specific causes of fecal contamination, which can come from any number of sources. Septic tanks percolating into groundwater, overflow from wastewater treatment plants, and runoff from a confined cattle-feeding operation are usual suspects for fecal contamination of water. Deer and elk droppings, as well as waste from water birds, dogs, and cats, also have been blamed for water pollution problems, the news release states.
“Traditional testing tells you that you have contamination, but not where it comes from,” explained Field, a microbiologist with OSU’s Agricultural Experiment Station. “The standard tests, growing fecal indicator bacteria such as E. coli, can’t distinguish between human, elk, bird, cattle, or pet-based fecal sources. And this is the kind of test that regulations are still based on. The laws have nothing to do with the source of the contamination.”
Tillamook Bay typically suffers chronic nonpoint fecal contamination that periodically poses risks to human health and the area’s shellfish industry, according to the news release. Previously, no one could pinpoint the source of the water pollution problem beyond the association with coliform bacteria, found in all warm-blooded animal feces. Field chose this coastal region to try out her new techniques and help ease a local environmental health problem.
Results show that in the majority of the Tillamook watershed, cows are the most important source of contamination, although human wastewater occasionally is a problem, especially in the bay and near the towns, Field said.
“Now managers on the north coast can focus on fixing the big problems — mitigating runoff from cattle, fixing fences, and improving drainage problems,” Field said.
Field’s group has developed genetic markers for bacteria from several host species. They can now assay polluted water samples directly for the presence of the marker genes, revealing the source of the fecal contamination.
With a new patent, Field is now focusing on developing a simple kit that contains everything needed to perform the test. She also wants to expand the number of genetic markers to include all the animals likely to be a source of contamination, even marine mammals and wild birds. Dogs, she noted, are a major issue for urban nonpoint source fecal pollution, and cat litter has been implicated in a die-off of sea otters in Northern California.
Contact Field at firstname.lastname@example.org. Read more about her research at aem.asm.org/cgi/content/abstract/72/8/5537.
Getting to the Root of the Matter
Beyond our sight — but not beyond our control — the futures of farm fields unfold in crop root zones. This area immediately surrounding a plant’s roots is the site of physical, chemical, and biological activities that govern the plant’s growth and its influence on the environment.
To help growers make well-informed decisions, U.S. Agricultural Research Service (ARS) scientists in the agency’s Agricultural Systems Research Unit (Fort Collins, Colo.), created the Root Zone Water Quality Model (RZWQM) in the early 1990s.
Now Fort Collins scientists have developed RZWQM2, an enhanced version of the original water quality model that has been designed to serve an even larger audience with greater ease.
RZWQM2 simulates plant growth and the movement of water, nutrients, and chemicals within and around the root zones of agricultural cropping systems. By entering information about their systems, growers can estimate the environmental and economic impacts of a variety of management decisions, including tillage, crop residue management, crop rotations, and the timing and rate of chemical applications.
Read more about this research in the March 2007 issue of Agricultural Research magazine at www.ars.usda.gov/is/AR/archive.