Is it OK for my pets and livestock to enter and/or drink the water?

Cows in a field

There have been cases in Missouri of livestock and pet illness and death linked to harmful algal blooms or HABs. If algae scum is floating on the water, block access to the affected water and provide another water source for them to drink or play in. If your animal comes in contact with blue-green algae, wash them off with fresh water immediately.

How can I keep my pets or livestock safe?

Before allowing pets to swim in lakes, rivers or at beaches, check for posted water quality condition information. This information may be online, at the park office or posted at common access area, such as bath houses or boat ramps. Also, educate yourself on harmful algal blooms and what to look for. If the water doesn’t look or smell right or you suspect a bloom is occurring, it is best to avoid direct contact with the affected area. Don’t let pets drink or play in the water, or roll in or eat the algae, even if dried. Dogs can also be affected by licking their fur after having been in contact with the scum. 

If the affected waterbody is a farm pond used for watering livestock, it is best to prevent them from accessing the pond by temporarily fencing it off, and providing another source of fresh water.

What should I do if my pet or livestock have been in contact with affected waters?

The symptoms animals may experience will depend upon the type of toxin present and how the animal was exposed. The severity of the symptoms will depend upon the amount of toxin ingested, the animals body size, amount of food in the stomach and the sensitivity level of each individual animal.

Common symptoms include:

  • Vomiting
  • Diarrhea
  • Rash
  • Difficulty breathing
  • General weakness
  • Liver failure
  • Seizures
  • Drooling

In the worst cases, animals may suffer convulsions and die.

Symptoms generally begin minutes to hours after exposure to the toxins.

If you are concerned your animal(s) may have been in contact with or ingested contaminated water, wash them off with fresh water immediately and contact your veterinarian. Let your veterinarian know you animal(s) may have been exposed to blue-green algae, or cyanobacteria.

Why are animals more susceptible to cyanobacteria toxins than humans?

Animals are more susceptible to algal toxins because they are more likely to drink, swim or play in contaminated water. They are not deterred by the unpleasing aesthetic appearance or smell of a bloom. They also tend to take in larger quantities of water or scum in comparison to their weight, so the toxin effects are more acute. 

Is it safe to eat the fish?

Fish caught in affected waters pose unknown health risks and may have an undesirable taste. Because of the unknown risks, we recommend you do not eat fish from affected areas for two weeks after the bloom visually dissipates. If you choose to eat them, remove all fat, skin and organs before cooking because toxins are more likely to collect in these tissues. Always cook fish thoroughly.

Do HABs affect aquatic life?

Any algae bloom, whether toxic or not, can lead to low oxygen levels in the waterbody. This can lead to high mortality rates in fish, shellfish, invertebrates and plants. Dense blooms can affect the amount of light that can penetrate into the water, adversely affecting plants and other organisms living on the bottom.

Additional Information

Veterinarians and Other Animal Health Professionals


When in doubt, report and stay out!