Association’s Update: E.coli Count as of 8/18
Last week we reported on the status of the E. coli O157:H7 outbreak investigation and shared the information available at that time. Lake Wildwood Association is in daily contact with the County Health Department and Environmental Health. The Health Department has primary responsibility for conducting the investigation working closely with Environmental Health. The Association is doing all it can to assist in any way possible. Some preliminary data have been reported connected to the outbreak investigation and the first test results related to the sewage spill have been reported. The E. coli O157:H7 outbreak and the sewage spill are unrelated issues.
The sewage spill on Sunday August 13 was caused by a power outage and occurred near the lift station in the green-belt on Chaparral Circle. The sewage flowed into the Lake at a point to the east of the lift station. It appears the sewage plume was then carried in a southeasterly direction toward the inlet of Lake Wildwood Creek, most likely due to wind drift. Results from the first water tests conducted by the County on Monday August 14 are summarized below. Upstream refers to the direction toward the Lake Wildwood Creek inlet. Downstream refers to the direction on the opening of Lake Wildwood Creek Bay into the main body of the Lake.
August 13, 2017 Sewage Spill
E. coli Test results for Samples Collected August 14, 2017
Sample Location (E. coli MPN/100 mL)
—300 feet upstream 2,419
150 feet upstream 1,986
Point of entry 1,553
150 feet downstream 579
300 feet downstream 199
Single sample recreation permissible maximum 235 MPN/100 mL
The E. coli indicator bacteria test results appear to indicate the sewage was “pooling” in the end of the bay at that time. All test results from the point of entry and upstream of that point were well above the recreational water limits. The downstream concentrations were elevated but suggest greater dilution in that direction. Samples were collected again on Thursday, August 17 and will be reported when received. Samples collected by the Association at Explorer Park Beach on Tuesday, August 15 did not show elevated E. coli levels.
The outbreak investigation is in full swing now. The last known exposure reported was July 23. The Lake was still open for swimming until July 28. No cases have been reported to us arising from people using the Lake between July 23 to 28.
Water, sediment and animal scat samples have been sent to multiple labs including Placer County Health Department, the State Public Health Lab and the Centers for Disease Control (CDC). The CDC shipped specialized sampling equipment to our local Environmental Health to concentrate large volumes of water. Concentration improves the detection sensitivity. These concentrated samples will be tested for E. coli O157:H7. Sediment/sand samples were also shipped to CDC. Results are expected in the next couple weeks.
We have received preliminary test results from animal scat samples submitted to Placer County Health Department Lab. Please note, these are preliminary test results and only represent a small fraction of the investigation in progress. Seven samples, four (4) deer and three (3) goose, were tested. Five samples were collected around Commodore. One each of deer and goose scat was collected at Meadow Park. All samples were negative for E. coli O157:H7 by standard laboratory test procedures.
In addition to conducting the standard analyses, the samples were also tested using newer molecular biology techniques (PCR). PCR procedures detect genes. The samples were tested for the presence of genes that encode for shiga toxin production. Shiga toxin genes were detected in all scat samples, but not related to E. coli O157:H7. This is where the science becomes very challenging. A gene may be present but not express itself. Work is continuing to try to determine what bacteria in the deer and goose scat may possess the toxin gene and what the health significance may be. That is currently unknown. At this point we can say a direct link has not been established between the E. coli O157:H7 infected children and adults to the deer and/or geese. Again, these are preliminary test results and much more work is in progress. No final conclusions should be drawn based on these data.
In addition to the animal scat testing, one water sample from Commodore Beach was submitted to the Placer County Health Department lab at the very beginning of discovering a link between the outbreak and the Lake. E. coli O157:H7 was not detected in that water sample. Much more water testing is currently underway.
Lake Wildwood Association can do little to investigate this outbreak other than assist the Health Department wherever possible. In response to the outbreak, we have increased our routine E. coli indicator testing of the Lake. We routinely tested weekly at each Park at the rope-line of the swim zone, and the creeks flowing into the Lake. We have increased our testing to include taking samples in the shallow water at the shoreline and at a point about waist deep (~3 feet) roughly midway between the shore and the rope-line depending on the beach. E. coli test results for this week show there was no difference between samples collected at the rope-line and those collected at waist depth, and all were well below the recreational limits. The shoreline samples at Hideaway and Vista were very low. Shoreline samples at Explorer and Meadow Park were elevated compared to the deeper water, but still below the recreational limit. The shoreline sample at Commodore was significantly above the limit. The outbreak investigation is examining reasons for the elevated shoreline concentrations and whether this is related to the outbreak. No direct link has been established yet.
Our test data continues to indicate there is no generalized contamination in the Lake. The significance of elevated E. coli levels at the shoreline is still not known. The source of the E. coli O157:H7 remains unknown. Given these uncertainties, the Health Department advisory will remain in place. The advisory was issued to protect your health. The Association recommends you heed the warning until these questions are resolved.
–Lake Wildwood Association
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