Public Health preps for next swim season

“We’re going to emphasize some prevention, so hopefully we’re not getting ourselves into a situation like we were this year,” Armstrong said.

The three presentation points in the “Swim Safety Campaign Spring 2019” were:

• Working with the public information officer to have focus messages during a month this spring.

• Focus on educating parents about swim diapers, reminding to take on frequent bathroom breaks, and other healthy swimming behaviors.

• Work with Green Neighbors Program to provide education on natural gardening (which Armstrong said could help prevent chemical runoff).

The presentation also outlined the response, investigation and testing timelines for the warnings and closures this summer.

While Battle Ground Lake was tested and had its health advisory lifted, the report hypothesized that it was most likely the source of the two initial Clark County cases of shigellosis bacteria, which is spread through fecal-oral transmission.

The investigation is ongoing, and case counts are subject to change, Armstrong said. There have been 15 total shigellosis cases: seven primary, and eight secondary. Primary cases are contracted through swimming, while secondary cases were sickened by primary cases.

Public Health was notified of the two Clark County cases on July 20, after the people swam in the lake on July 14. Testing was conducted within hours of notification, but “by then the water sampled didn’t show anything,” Armstrong said.

That conclusion was strengthened by the fact that during the investigation, the mother of the two Clark County cases reported her children saw fecal matter in the water. Multnomah County also reported three shigella cases in people who swam in Battle Ground Lake on the same day as the Clark County cases. Shigella has appeared in Clark County bodies of water before — Klineline Pond in 2012 and 2014.

Data collected by Public Health also shows that high temperatures and the increased need to cool off in water didn’t help. The highest temperatures this summer probably drew the biggest bather loads at Klineline, because that’s when the most transactions happened. Transactions are measured through how many people paid to park at Salmon Creek Regional Park.

Those transactions are used as a proxy for bather loads, since parking doesn’t necessarily mean those people swam in the pond. When there were an increased number of transactions, there were higher plate counts of E. Coli present, and the increased E. Coli counts can be attributed to a higher bather load, according to the presentation.

“When temperatures rise, more people head to these water bodies,” Armstrong said. “We’re going to try to emphasize education about swim behavior and human behavior. … Nobody wants to see the swim beaches closed.”