Professor Valerie Harwood of the
Department of Integrative Biology.
USF microbiologist silences critics
TAMPA, Fla. -- University of South Florida microbiologist Valerie Harwood wasn’t looking for a fight with some of the nation’s poultry giants when she accepted an unusual assignment from the Oklahoma Attorney General’s Office: investigate whether millions of pounds of chicken waste from giant farms could have infiltrated Oklahoma’s watershed and polluted its lakes, streams and wells.
Harwood, who over the last decade has developed a technique to track E. coli and other sewage contaminants and connect them to a specific source, was employed as a scientific expert from 2005 to 2008 by the state of Oklahoma to look for connections between potentially deadly bacteria in the Illinois River watershed to massive poultry operations in neighboring Arkansas and in Oklahoma.
Big poultry fought back, seeking to dismiss Harwood’s work as “junk science” because a new, poultry-specific technique had not been published in a peer-reviewed journal.
Fast-forward to 2011: the court case is still awaiting a decision but the verdict on Harwood’s science is in: the first in a series of articles was published in the Journal of Applied Microbiology and a second paper has been accepted in the journal Applied and Environmental Microbiology.
The publications are a milestone for Harwood, a well-respected expert on water quality and contamination who had her credibility under a microscope during the contentious case. Eleven poultry companies, including chicken giant Tyson Foods Inc., are defendants in the lawsuit.
“If you can find a source-specific microorganism, you can trace (the pollution),” she said. “It’s a lot easier said than done, but it can be done.”
Harwood, a professor in the Department of Integrative Biology, had been an expert witness called by the state of Oklahoma to test E. coli in the Illinois River and compare it to bacteria in the hundreds of thousands of tons of poultry waste which is used as fertilizer on farms and ranching operations near the chicken farms.
Harwood was already an internationally recognized expert in microbial source tracking -- a field of environmental microbiology that seeks to determine the source of fecal contamination in water by identifying specific molecular signatures in the DNA of fecal microorganisms -- when she was called into Oklahoma’s case. The tactic used by the poultry companies was effective: a judge denied Oklahoma’s request for an injunction and the case has lagged on for years with the same practices continuing.
Working with researcher Jennifer Weidhaas, now at West Virginia University, the scientists’ test is based on quantitative PCR and can determine the level of Brevibacterium LA35 in rivers and streams. Harwood explains that this type of bacteria is highly concentrated in soiled poultry litter and is otherwise uncommon, allowing the bacteria to serve as a tracer for poultry fecal contamination that spreads to water bodies after the poultry litter is spread on fields.
Harwood said the contamination has spread into neighboring Oklahoma through rain washing it into ditches and tributaries, then flowing into the Illinois River, a scenic Oklahoma water that is home to many recreational activities. The porous nature of the area’s karst geology also allowed contamination to seep into the groundwater.
“The biggest surprise to me was that I did not realize what a prevalent practice this is,” she said. “They are spreading literally tons of this material every year. It’s amazing to me that anybody thinks this isn’t going to end up in the water.”
The most recent article encompasses the scientific results drawn during Harwood’s work on the Oklahoma case. Her work took her to an area of Arkansas and Oklahoma where some 1,600 poultry farms housed more than 57 million chickens and turkeys -- some 2 percent of the nation’s poultry supply.
Using the marker, the scientists established that the poultry feces marker was correlated with E. coli and other fecal bacteria in litter samples and water samples from the Illinois River watershed, and with phosphorus and heavy metals prevalent in poultry feed in water samples.
Poultry producers could alleviate the pollution by using other disposal techniques rather than selling the poultry litter to farms and ranches as inexpensive fertilizer, Harwood said. For example, if the litter were composted, a process which raises the temperature of the material, the bacterial load would be reduced. Or, the industry could truck the waste to a disposal site that was not near vulnerable water bodies.
Either technique, however, would raise the cost of poultry at a time when inexpensive protein food sources are a necessity just not for the United States but much of the world. And while the problem of poultry waste disposal may remain a challenge, Harwood said she hopes her scientific evidence empowers consumers to consider the impact of large-scale farming and food choices on the environment.
On that count, there’s already an early verdict.
“I got e-mails from citizens thanking me for doing this,” she said.
Author: Vickie Chachere