It looks like Fido can go swimming again with the removal this week of signs along the Russian River warning visitors about a toxic blue-green algae that killed a dog in August.

Sonoma County Health Services officials say water and weather conditions no longer favor growth of the cyanobacteria blamed for the Aug. 29 death of a golden retriever named Posie.

Health and water quality officials halted testing in the river a month ago after several weeks of negative results for the dangerous organism and the potent neurotoxin it produces, called Anatoxin-a.

Cooling temperatures and water conditions since then suggest the risk is no longer present, health officials said.

“We feel that the water is safe and will remain safe going forward through the fall and winter,” Sonoma County Deputy Health Officer Karen Holbrook said Thursday, “so we felt comfortable removing the signs.”

Blue-green algae and the threat of exposure to Anatoxin-a, which is said to cause symptoms similar to those caused by military nerve gas, have appeared this year in a number of California rivers and water bodies, including the Eel River in Mendocino County.

Scientists say hot temperatures and drought-era low water levels have combined to create warm, still pools that foster its growth.

Ingestion or aspiration of Anatoxin-a can cause abdominal pain, nausea, diarrhea, sore throat, headache, dizziness, seizures and a host of other problems. It can prove fatal within minutes.

Dogs are considered particularly vulnerable, because they are prone to drinking the water while they swim and they lick themselves after swimming, potentially exposing them to the neurotoxin.

In Sonoma County, blue-green algae was detected in August in mats of otherwise harmless algae in the Russian River. Health officials notified the public about its presence Aug. 20.

Then Posie, who was on a canoe trip with her owners from San Jose, died Aug. 29.

Health officials decided on the eve of Labor Day weekend to keep the Russian River beaches open, but posted warnings at 10 popular beaches about the danger to dogs, babies and even adults of ingesting water that contained the neurotoxin.

Widespread media publicity had significant impact on Labor Day tourism and its aftermath, some business owners say.

Holbrook said public health and North Coast Regional Water Quality Control Board personnel would put their heads together before next summer to review events of this year and coordinate future plans for monitoring river quality and managing any necessary response.

“Maybe it’s a complete replication of what we did this year,’ Holbrook said. “Maybe we can improve upon that.”

You can reach Staff Writer Mary Callahan at 521-5249 or On Twitter @MaryCallahanB.