Algae Poisoning

Cyanobacteria (also known as blue-green algae) produce toxins which can be deadly to chickens if ingested in large amounts. It can grow in any stagnant water source, such as poultry waterers, water troughs, buckets, ponds, lakes, baby pools, etc. Blue-green algae is more likely to grow rapidly when the stagnant water source is exposed to high temperatures, sunshine, and any sort of organic matter or debris.

The algae forms in large colonies that appear as scum on or just below the water source. The presence of bacteria often may be determined by a bluish tinge to the water. Concentrations of bacteria often are bluish green but may vary from dark green to brownish green, depending on the total bacterial population. In lakes and ponds, proliferation of blue‐green algae may result in a “bloom”, which is a build-up of algae that creates a green, blue-green, white, or brown coloring on the surface of the water, sometimes occurring as mats or scum. It may look like a floating layer of paint.

Cyanobacteria can produce two types of toxins, microcystins and anatoxins. Microcystins (hepatotoxins) affect the liver and anatoxins (neurotoxins) target the nervous system. The toxins enter the chicken’s body when they drink the affected water. The clinical signs of poisoning depend on which toxin is involved.

Hepatotoxins can severely damage the liver leading to organ failure, which can occur quickly or over several days. Clinical signs of exposure to the hepatotoxin may non-specific such as lethargy, loss of appetite, weakness, and pale comb, along with diarrhea and bloody or dark droppings.

When neurotoxins are ingested, signs of poisoning occur within 30-60 minutes of ingestion and death within minutes to hours after exposure. Since neurotoxins target the nervous system, signs such as muscle tremors, paralysis, and seizures may occur. Decreased oxygen delivery makes it difficult for the bird to breath, and causes the chicken’s comb to change to a crimson to purple color.

If chickens are suspected of having been exposed to blue-green algae, a veterinarian should be contacted immediately. If caught before signs occur, administering activated charcoal orally may help absorb the toxin.