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Microbial source tracking: Conservation districts discuss progress and plans

by Wyoming Livestock Roundup

Casper – Microbial source tracking (MST) has been implemented in several districts across Wyoming in the last couple years, according to Cathy Rosenthal, Wyoming Association of Conservation District (WACD) watershed coordinator.

Rosenthal hosted the MST session during the Progressive Resource Manager Forum at the Wyoming Natural Resources Rendezvous on Nov. 27 in Casper to review the last two years of MST.

“MST is a more specific method of determining microbial sources, like E. coli, compared to other similar methods,” Rosenthal explained.


Crook County Natural Resource Department (CCNRD) District Manager Raesha Sells discussed MST sampling in Crook County from the past two years.

“CCNRD conducts water sampling on the Belle Fourche River and Donkey Creek, where there is a total maximum daily load (TMDL) in place for E. coli, chloride and ammonia,” she said.

The Environment Protection Agency (EPA) requires a TMDL when an impaired water body is not removed from the impaired water body list after eight to 13 years, according to Rosenthal.

CCNRD hasn’t conducted MST sampling since 2015. MST was originally conducted to determine to source of E. coli in the Belle Fourche River and Donkey Creek, explained Sell.

“Eight different markers were tested looking for canine, ruminant and human sources. In 2015, the results showed one human hit, 11 ruminant hits and six canine hits,” she noted, adding CCNRD correlated data with Campbell County Conservation District for the canine and human results.

According to Sells, MST has been difficult for CCNRD to use for ruminants because the markers are not specific to cattle, sheep or wildlife.

“Due to the broad scope of MST markers, CCNRD discontinued MST sampling until more specific markers could be developed,” stated Sells, adding best management practices with landowners are being used to reduce E. coli within the watershed.

Tiered approach

Both Campbell County Conservation District (CCCD) and Popo Agie Conservation District (PACD) implemented MST tiered approaches.

“In 2006, CCCD spent grant funding to fix septic systems, but E. coli was still a problem, so we started using the MST tiered approach to find the human source,” stated Jay Quintanilla, CCCD water and range technician.

For two years, CCCD MST sampled the Little Powder River for human E. coli sources, resulting in zero human hits. CCCD decided to implement best management practices in that area to direct funds into a more cost effective project, according to Quintanilla.

“MST is a valuable tool that gives us some confidence to tell stakeholders there isn’t a major problem,” he added.

In 2017, Quintanilla stated CCCD moved up the tiered approach by investigating avian E. coli sources because there were a lot birds at all of the MST testing sites.

“We were only able to obtain five days of sampling for avian sources, so we will continue with the avian approach in 2018,” he stated.

In PACD, E. coli has been monitored since 2002, and best management practices were implemented to help reduce the concentration.

“We realized that to implement targeted best management practices, the E. coli source needed to be located,” stated Dave Morneau, PACD conservation technician.

He said PACD was directed to look more at human sources in 2006 and some key projects were implemented, but the data was inconclusive.

“We decided to try source identification, and MST was emerging but we decided to try a different method instead,” he added.

PACD also used the tiered MST approach for three years, but their approach was too narrow, according to Morneau.

“Currently, the samples haven’t been from definitively positive sources, so we have enhanced our sampling protocol,” he stated, noting PACD will be focusing on livestock.       


Quintanilla stated he thinks MST isn’t the best approach when there is a known E. coli source.

“CCCD is constantly observing wildlife, and we know that agriculture is a huge sector in the area, so MST isn’t always necessary,” he said.

He also mentioned MST has spatial and temporal limits.

“In Gillette, there is a sewer treatment plant, and we know there is human waste coming out of the area, but when CCCD samples downstream, there isn’t any trace of human sources,” explained Quintanilla.

Morneau also voiced his concerns with the sensitivity of the human marker tests, but PACD is moving forward in the belief there isn’t many human sources of E. coli.

“PACD is also concerned about the results between Microbial Insights, a lab in Tennessee, and the Wyoming Public Health Lab because the numbers were different,” he added.

Morneau concluded, “Just because there aren’t positive hits doesn’t mean there’s nothing to be learned. Negative hits are helpful, too.”

Heather Loraas is assistant editor of the Wyoming Livestock Roundup and can be reached at

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