Botulism kills birds by thousands in France this summer, unheard of in 30 years: what is this disease

“Global warming could generate an increase in the number of botulism episodes In wild fauna, “warned the National Agency for Food, Environment and Labor (ANSES) a few years ago. This summer 2025, marked by a heat wave from June 19 to July 4 – one of the earliest and intense, (just behind July 2029 and August 2003) – seems to confirm it.

In Loire-Atlantique, it is the massacre: the climatic conditions “combining hot weather and episodes of drought” A mortality of wild birdsespecially on Lake Grand Place and on the Brière marshes, explains our local editorial staff The echo of the peninsula. More than 3,000 corpses of birds have been collected in recent days.

A bacteria that develops in hot weather in stagnant waters

When temperatures climb, the water of the ponds becomes warmer. The dissolved oxygen level decreases and the conditions become more favorable to the spore germination and at The proliferation of botulinum toxinsummarizes the ANSES.

The results of the samples of this month of July 2025 on Lake Grand Place highlighted an avian botulinum toxin, synonymous with botulism. This disease is transmitted by the ingestion of this botulinum toxin, naturally present in wetlands, but developing in hot weather in stagnant waters.

Botulism provokes “a Skeletal muscles paralysis animals that can lead to death by respiratory failure or drowning ”, explains the Brière Regional Natural Park.

Stewed propagation as quickly as possible

Avian botulism is not transmitted to human beings or mammals. L‘challenge, to date, is however to pick up the deceased animals as quickly as possible to stem.

Botulism is a human and animal neurological disease caused by the action of bacterial neurotoxins (botulical toxins) produced by bacteria of the genus Clostridium and which manifests itself by flabby paralysis that can go as far as respiratory paralysis and cardiac arrest. There are nine known types of botulical toxins. Animal botulism in France mainly concerns birds (wild and breeding) and cattle.

If some cases of avian botulism are not “unusual” in summer in Loire-Atlantique, such mortality had not been observed Since 1995Éric Provost, president of the Brière regional park who has some 25,000 hectares of wetlands, interviewed by AFP.

Too low a water level in the marsh

Considered “The most important disease in terms of mortality For global -scale water birds, “avian botulism can cause the loss of tens of thousands of individuals during an episode, according to ANSES.

Éric Provost notably points to agricultural uses which, according to him, keep a water level too low in the marshes, for breeding and fodder. The manager of hunters in the sector does not deny these “conflicts of use” but above all believes that it is an “water regulation” unsuitable for an exceptional year that is involved.

In January, we have practically reached the highest levels of water known on the marsh since we have made surveys. And there, at the end of June, we got closer to the lowest water levels.

For him, “the water regulation, very clearly, is not designed for this type of year”, which may become more and more frequent with climate change.

Several cases of botulism in humans in recent years

Botulism in humans on his side remains a very rare food toxi-food in France. Fatal in 5 to 10 % of casesthis disease is caused by a very powerful toxin produced by a bacteria that develops in poorly preserved foods, for lack of sufficient sterilization.

In September 2024, five thirty-something had been hospitalized in serious condition following a birthday meal during which they had consumed preserves of pesto at the bear’s garlic, in Indre-et-Loire.

In September 2023, 16 customers (including a woman who died of it) were identified as “suspect cases of botulism”, after having eaten sardines in handcrafted manufacturing in a tourist restaurant in the center of Bordeaux (Gironde).

It is advisable to wash food and cook them well

Prevention measures are based on compliance with hygiene rules relating to Preparation and conservation foodstuffs, in order to prevent the development of bacteria C. botulinumas well as the production of toxin.

To prevent food intoxication, it is advisable to:

• Wash food;
• Cook them well (toxins are destroyed during prolonged boil);
• Use clean water;
• Keep food at an adequate temperature.

Spores of C. botulinum that can be in honey, it is recommended not to give children under a year.

With AFP

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