Toxic algae test results are in after mysterious deaths of California family while hiking

Sep. 8—Few clues have been shared by investigators working to determine how a family and their dog died a little over three weeks ago while hiking in Sierra National Forest, in a remote section of Mariposa County southwest of Yosemite National Park.

Known harmful algae blooms in the south fork of the Merced River, near where the family was mysteriously found dead along the Savage-Lundy Trail in Devil's Gulch, are among the hazards being considered.

Mariposa County Sheriff Jeremy Briese, in a monthly update last week, said some test results from recent water samples there came back showing "high levels" of anatoxin-a, but that investigators are "not saying" that's what killed Mariposa residents John Gerrish, Ellen Chung, their daughter, Miju, and family dog, Oski.

Anatoxin-a, sometimes called Very Fast Death Factor, is produced by cyanobacteria caused by harmful algae blooms.

"The signs of toxicity were mostly neurologic," the U.S Environmental Protection Agency wrote in a report about the health effects of anatoxin-a, "with deaths due to respiratory paralysis. ... In oral toxicity studies, animals demonstrated acute clinical signs of neurotoxicity such as loss of coordination, muscular twitching and death from respiratory paralysis within several minutes of exposure."

Briese said the presence of anatoxin-a was reported to the State Water Resources Control Board.

A state map of harmful algae blooms across California was updated Wednesday afternoon with results from samples taken Aug. 19 on the south fork of the Merced River, north of Jerseydale.

Despite the presence there of anatoxin-a, the State Water Board said it's continuing to recommend a caution advisory in that location, near where the family was found dead, which is two tiers below the state's most serious danger advisory.

"Multiple types of cyanobacteria were detected" in algal mats there, the results state, along with anatoxin-a at 11.8 micrograms per liter.

"No other cyanotoxins were detected (I.e. microcystins, cylindrospermopsin, saxitoxin)," the results posted Wednesday continue. "Recommend continued posting of toxic algae alert advisory at recreation access points to this site and follow up monitoring to inform advisory postings."

Advisory recommendations for that area are: "Stay away from algae and scum in the water. Do NOT let pets go in the water, drink the water, or eat scum on the shore. Keep children away from algae. Do not eat shellfish from this waterbody."

The listing notes that the "related illness investigation is ongoing."

Jackie Carpenter, a State Water Board spokesperson, shared more from her staff, stating, "We were not involved in, nor do we have the results from, other subsequent testing that may have been carried out by the county or other agencies. Both the data collected on 8/19 and results have been shared with Mariposa County; all investigations into the underlying matter are led by the county."

Additional water samples were collected Aug. 23 in the area where the family was found dead, Mariposa County Sheriff's Office previously said. The sheriff's office said there was no new information to share Wednesday about the mysterious death case.

Sierra National Forest closed numerous hiking trails, picnic areas and campgrounds on Aug. 29, citing "unknown hazards found in and near the Savage Lundy Trail," where a Mariposa family was mysteriously found dead. Those Sierra National Forest closures will be in effect until at least Sept. 26 — longer than a statewide order that followed shortly after, about the closure of all national forests in California due to increased wildfire danger.

A Sierra National Forest spokesperson on Tuesday said just that the hazards are "still under investigation." The agency has not answered questions about the size of the known harmful algae bloom on the south fork of the Merced River, or if there are others in Sierra National Forest.

There are dozens of harmful algal blooms across California, including Hensley Lake in Madera County, and San Luis Reservoir in Merced County. Both are listed under the state's most serious danger advisory.

The results of toxicology tests for the Mariposa family have not been shared.

In response to a question during Thursday's sheriff update, about whether toxicology results were back yet, Briese said, "Some are, yes. But we still do not have an exact cause of death yet."

One resident asked whether the poisonous algae could affect well water in the area. Briese said he was unaware of any wells nearby the harmful algae for a "long long way," but that residents should contact the Mariposa County Environmental Health Unit if they have concerns or questions.

In response to another question, Briese said he hadn't heard of any livestock dying from harmful algae in Mariposa County, but the recent tests from Devil's Gulch showed that "the levels were high, especially dangerous for animals."

The state health department reported that while animals have been poisoned from algae, "no known human fatalities have been documented from recreational or drinking water exposure to cyanobacterial toxins."

Another resident asked for recommendations for taking safe walks alone in Mariposa County. Briese advised to always let someone else know where you're going, know your route, bring water and stay hydrated, and that carrying pepper spray or bear spray as a precaution can be helpful.

The sheriff's office last month ruled out weapons and "chemicals hazards" along the Savage-Lundy Trail in the deaths of the Mariposa family, adding, "ALL other potential causes of death remain."

Briese said detectives have been working "around the clock" to determine what killed the family, and that his department has been getting lots of help from state and federal partners, including the FBI.

The Mariposa County Sheriff's Office serves a rural, mountainous county. The department has a minimum five sheriff personnel patrolling Mariposa County each day, Briese said.

___

(c)2021 the Sierra Star (Oakhurst, Calif.)

Visit the Sierra Star (Oakhurst, Calif.) at www.sierrastar.com

Distributed by Tribune Content Agency, LLC.