Currently in Idaho there are seven bodies of water with active health advisories because of cyanobacterial harmful algal blooms (cyanoHABs). However, there may be other blooms that have not been identified, and people should exercise caution to avoid getting sick or exposing their pets or livestock.

CyanoHABs or just “harmful algal blooms (HABs),” occur most often during the summer months and into early winter, when there is a lot of sunlight, and water is warm, stagnant, and full of chemicals (nutrients) that blooms thrive in. Blooms often produce toxins, called cyanotoxins, which can be dangerous for humans, animals, and the environment. 

How sick can I get if exposed to a bloom?

The most common health effects from contact with harmful algal blooms are irritated skin and eyes. Other, more serious symptoms can include:

• Difficulty breathing
• Stomach pain
• Nausea
• Vomiting
• Diarrhea
• Dizziness
• Numbness and tingling in lips, fingers, and toes

If you experience mild irritation, rinse the area with clean water immediately. If you experience severe symptoms, seek medical attention as soon as possible.

How can I tell if my animal is sick from a bloom?

Pets and livestock that come across harmful algal blooms can get very sick and die within hours to days after swallowing water with cyanotoxins in it. Signs in animals include: 

• Weakness
• Staggering
• Foaming at the mouth
• Difficulty breathing
• Convulsions and seizures

Pets, wildlife, and livestock can be impacted much more than people because they intentionally drink from water where cyanoHABs tend to occur. Additionally, cyanobacteria and their toxins can become trapped in an animal’s fur while swimming and then swallowed afterward when they clean themselves. 

If you suspect your pet has been in contact with a bloom, rinse them with clean, fresh water immediately. If they show signs of illness, call a veterinarian. In severe cases, animals can die very quickly after they have been exposed to harmful blooms. 

Click here for more information about animal safety.

What do blooms look like?

• Blooms can be blue, bright green, brown, or red. 
• They might look like paint streaks across the surface of the water or have the appearance of pea soup, foam, scum, or mats on the surface of lakes and ponds. 
• You might see dead fish or other animals washed up on the shore of the body of water.
• Blooms also occur as mats clinging to rocks and debris at the bottom of water, where they are more difficult to see. In these cases, the water can appear clean and clear. 

Is it safe to eat fish from a lake with a bloom?

If you choose to fish in water with a bloom, prevent exposure by wearing gloves or waders, and washing your hands thoroughly with clean water after handling fish. Information about the risk of eating fish from affected waters is limited. However, fish fillets are less likely to have toxins compared to other parts of the fish. If you decide to eat fish from affected water, before cooking:

• Remove the skin, organs, and fatty deposits from the fish.
• Avoid cutting into organs while you’re cleaning the fish.
• Rinse the fillets with clean water.

Click here for more information.

How can people avoid a bloom?

• Check active advisories by visiting the Idaho Recreational Water Health Advisories website.
• Look for signs posted around recreation sites.
• If the water matches the description of cyanoHABs listed above, or looks different than expected, do not enter or allow your children, pets, or livestock to go in or near the water. When in doubt, stay out. That goes for your pets, too!
• Avoid water sports in areas with a cyanoHAB. Swallowing water is not the only way it can make you sick. Contact with skin, or breathing in water particles, such as while waterskiing or tubing, can also lead to illness.
• When recreating, bring fresh drinking water. Do not use untreated water for drinking, bathing, cleaning, or cooking for you and your pets. Boiling contaminated water will not remove the toxins and can cause more toxin to be released.

Resources:

• Recreational Water Health Advisories
• Information from the Centers for Disease Control and Prevention
• Report and view HABs near you
• Idaho Fish Consumption Advisories
• DHW Cyanobacterial Harmful Algal Bloom FAQ

Will Reynolds is a health program specialist in the Bureau of Environmental Health and Communicable Disease, Division of Public Health, Department of Health and Welfare.

The Idaho Department of Health and Welfare is dedicated to strengthening the health, safety, and independence of Idahoans. Learn more at healthandwelfare.idaho.gov.