Department of Health and Human Services

Safeguarding Children and Pets from Cyanobacterial Harmful Algal Blooms

Cyanobacteria are naturally-occurring microscopic algae that often grow in fresh bodies of water such as lakes, ponds and canals. Like plants, they can use the sun as an energy source. Small numbers of cyanobacteria can explosively grow into large numbers very quickly. This rapid increase is called a bloom. The bloom can become harmful to people, pets, livestock, and aquatic plants and animals by producing toxins, shading light, and clogging gills in fish.

Toxins produced by cyanobacteria can affect the kidneys, gastrointestinal tract, liver, and nervous system of people, pets, livestock and other animals. Children and dogs are the most vulnerable to the effects of cyanobacterial toxins. Dogs are especially susceptible to cyanotoxins that attack the nervous system. Deaths of dogs associated with cyanobacteria have been identified in North Carolina as recently as 2009. Inadvertently, dogs can also alert us to possible adverse human health effects due to harmful algal blooms.

By nature, dogs often play and wade in shallow areas of a pond or lake where algal blooms tend to concentrate due to wind and water currents, and where the toxins can become concentrated. Dogs usually become exposed to the toxins by drinking bloom waters or eating the algae. Algal toxins can be lethal to a dog.

Young children also play and wade in the shallow areas of ponds and lakes, and are exposed to toxins by ingesting bloom waters containing toxin. Due to their size, children may have adverse health effects from smaller amounts of toxin than would affect an adult.

No reports of adverse health effects in children associated with cyanobacterial blooms have been identified in North Carolina. That may be because people generally avoid bloom waters, while many animals do not.

Under select conditions, the state may test public recreational, ambient or drinking waters for microcystin, the most common type of cyanobacterial toxin. Local health departments, public water supplies, and state agencies may request testing through the Occupational and Environmental Epidemiology Branch of the N.C. Division of Public Health. A water body with a visible discoloration of the water or a surface scum may be considered for microcystin testing. Bloom waters may also be tested whenever there are animal deaths (especially dogs) or human health effects associated with bloom waters.

When algal blooms are tested by the state, they usually contain at least a low concentration of toxin. Therefore, the safeguards below are recommended for children and pets:

Steps to safeguard your pets and children from harmful cyanobacterial (algal) blooms:

• Keep children and pets away from waters that appear discolored or scummy.
• Do not handle or touch large accumulations ("scums" or mats) of algae.
• Do not water ski or jet ski over algal mats.
• Do not use scummy water for cleaning or irrigation.
• If you accidently come into contact with an algal bloom, wash thoroughly.
• If your pet appears to stumble, stagger, or collapse after being in a pond, lake or river, seek veterinary care immediately.
• If your child appears ill after being in waters containing a bloom, seek medical care immediately.
• If you are unsure whether or not a bloom is present, it is best to stay out of the water.

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