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Why are blue algae so dangerous for dogs? How to recognize them and avoid poisoning your pet?

Why are blue algae dangerous for dogs?
Blue algae, also sometimes called blue-green algae, are cyanobacteria. They are photosynthetic bacteria that use solar energy to make organic molecules, just like plants do.
Present everywhere on the planet; they inhabit the waters of rivers and oceans in a completely normal way. But, when they proliferate in too large numbers thanks to the hot summer months, water pollution and low water levels, they can become particularly dangerous for our canine friends. During efflorescence or “bloom” algal, these bacteria are then responsible for the production of two harmful toxins for their central nervous system (neurotoxin) or for their liver (hepatotoxin).
In summer, a dog can then become fatally intoxicated by ingesting standing water that contains it or simply by bathing in contaminated water.
Are cyanobacteria also dangerous for humans?
Yes, absolutely! Cyanobacteria are dangerous for everyone! According to the World Health Organization, these toxins are also very dangerous – although rarely fatal – to humans. In humans, they can cause skin irritation, stomach cramps, vomiting, nausea, diarrhoea, fever, sore throat, headache, muscle and joint pain, as well as the formation of vesicles around it—mouth and liver damage.
How to recognize cyanobacteria?
With the naked eye, one can spot these algae quite easily by observing the surface of the water on which they form a bluish/green layer.

  • Photo credit: By Lamiot – Own work, CC BY-SA 3.0, –
    They thrive in marine waters or in calm, nutrient-rich freshwaters during the summer months. The waters most affected are waters where nutrients from algae, such as nitrogen and phosphorus, have accumulated. This high concentration of nutrients is caused by the pollution of aquatic environments by agricultural spraying and by industrial and urban wastewater discharges.
    In these waters, the bacteria that accumulate form clusters (or flocs) preferentially in areas where water stagnates, such as a backwater of a river or a puddle of water.
    If you find yourself near a body of water contaminated by blue algae with your dog, you should therefore avoid coming into contact with and swallowing water at all costs.
    Are there any controls?
    In mainland France, several regions are regularly affected by algal blooms. It is the Regional Health Agencies in charge of controlling the quality of bathing water during the summer season, which generally gives the alert in the event of non-compliant sampling. When a high concentration of cyanobacteria in the water is found, the Authorities then take measures prohibiting swimming, all or part of nautical activities, or even prohibiting the consumption of fishery products resulting from the plan. Contaminated water. These prohibitions are generally materialized by display panels on the swimming site. But, be well aware. Those water analyzes are only carried out on sites authorized for swimming. If a body of water is not listed as such, then no controls are carried out. And no poster will warn you of the danger, which is nevertheless very present in the event of an algal bloom.
    Cyanobacteria poisoning in dogs: the signs
    Symptoms of dog poisoning by cyanobacteria may be neurological in nature if the algae involved are neurotoxic or hepatic if the algae involved are hepatotoxic.
    Neurotoxic algae can cause tremors, convulsions, breathing difficulties and hypersalivation. Unfortunately, they also often lead to respiratory paralysis, which can lead to the death of the animal very quickly after contact with blue algae (usually within 30 minutes).
    Hepatotoxic algae act between 1 and 4 hours after ingestion of contaminated water. They are the cause of very strong depression in the dog, vomiting and diarrhoea. Quite often, they kill the animal within 24 hours to a few days.
    My dog was poisoned by blue algae: what to do?
    Unfortunately, when poisoned by cyanobacteria, a dog’s health deteriorates very quickly and almost inexorably ends in death.
    But, by acting very quickly after poisoning or suspected poisoning, a veterinarian can initiate a treatment that aims to eliminate as many toxins as possible, relieve the dog’s symptoms and support his breathing. Do not waste a second to have any hope of saving your animal and lead it as quickly as possible to the open veterinary clinic closest to the place where the contact with the blue algae occurred.
    If unfortunately, your dog succumbs to poisoning, his death should be reported by the veterinarian to the Regional Health Agency.


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