Residents are asking questions after five cases of a rare and terminal neurodegenerative disease were diagnosed among inhabitants of a single street in a town in Somme (Pas-de-Calais).
The street, rue du Château d’Eau, is in the small village of Saint-Vaast-en-Chaussée, near Amiens.
Over the past 16 years, five residents of the same street have been diagnosed with a kind of motor neurone disease (MND) - called amyotrophic lateral sclerosis (ALS), which in France is known as maladie de Charcot.
The disease causes the progressive degeneration of nerve cells in the spinal cord and brain and the loss of the motor neurons that allow voluntary movement. Life expectancy at diagnosis is around three to five years, and can be much shorter.
However, renowned theoretical physicist Stephen Hawking lived with ALS for 50 years.
‘A lot of coincidences’
One resident on the street, Françoise Gamain, said that her husband was the first to be diagnosed, aged 67. He was diagnosed in October 2008, and died in March 2009.
“After the second case, we said that it was a coincidence. But after a few cases, we started to say that it seemed like a lot of coincidences,” Ms Gamain told BFMTV.
Overall, the national rate of diagnosis is 2.7 new cases per 100,000 people, or 8,000 people nationwide. However, there are only 500 residents in Saint-Vaast-en-Chaussée.
Investigations and surveillance
The town’s mayor, Marc Vignolle, called on the regional health body l’Agence régionale de santé (ARS) for help after the unusually-high number of diagnoses, and it launched an investigation.
In a statement, the ARS said: “The study allowed us to confirm a high number of cases of ALS in this commune.” Health authority Santé publique France said “investigations are underway”, and confirmed that it had launched specific health monitoring and epidemiological surveillance into the cases.
It said that it would investigate what it calls “a cluster report” to “determine whether there are one or more local causes for this grouping of cases, other than chance”. For the moment, no single cause has been formally identified in Saint-Vaast-en-Chaussée.
Mayor Mr Vignolle said that residents had been asking questions “but I don’t know anymore [than they do]”, he told local newspaper Courrier Picard.
Ms Gamain has wondered if the local environment could have caused the problem. She said: “There are fields around the house, could it be coming from there? Phytosanitary products? Something we ate? But if it is in the water or in the air, why does not it affect the other streets in the village?”
The daughter of one of the patients has called for more information.
Her father, a former ambulance driver who lived on the same street, died with ALS in 2022 at the age of 70. She said: “We haven't been told anything, we haven't had any explanation, we haven't been contacted by anyone, we have the impression that no research is being carried out.
“We feel helpless,” she said, adding that her aunt and cousin still live in the same street.
‘ALS is rare, but not exceptional’
But one neurologist, Dr François Pradat, from the Pitié-Salpêtrière hospital (APHP), told BFMTV that while the Saint-Vaast-en-Chaussée situation is “unusual” but still “statistically possible”.
“ALS is a rare disease, but not exceptional,” he said. “I have three ALS patients who belong to the same cycling club. I also have couples where both members develop ALS. But that doesn't mean there's any link. If I had five people with ALS living in my street, I wouldn't panic.”
The cause of ALS is not singular, experts say, and can be caused by both genetics and the environment. Dr Pradat said that around 10% of sufferers have a family history, and “there is a genetic susceptibility” with ALS, “as with all neurodegenerative diseases”.
He also added that not all the genes involved in the disease have been identified, so medical understanding of exactly what causes the condition is still limited.
He said that a wide range of “environmental factors” - such as smoking, high-level sport, pesticides, heavy metals, and even toxins in some algae - have been suspected to affect whether people develop neurological conditions, but that “there must be a favourable genetic landscape”.
One study suggested that eating a toxic mushroom could bring on the disease.
In 2021, a French-American report suggested a link between the ‘giant gyromitra’ mushroom, also known as false morel, in a cluster of ALS diagnoses in the La Plagne-Tarentaise area Savoie. Of the 14 people diagnosed between 1991 and 2013, all were found to have ingested the mushroom.
But Dr Pradat denied that this study showed “any statistical significance”, and that there was “significant biases” in this cluster, including “the age of the population, the time of exposure”, he said. “We often see stories of clusters of ALS, but they rarely come to anything”.
However, some studies suggest that toxins found in water may be linked with the disease. In 2013, a study on 381 ALS patients from Hérault found that diagnosis rates were higher in communes located close to the Thau lake, near a production area of mussels and oysters.
A neurotoxin, BMAA, was found in the lake - and the same toxin had been linked to cases of ALS on the Pacific island of Guam, after residents consumed seeds containing the same substance.
“There is a link between BMAA and ALS,” said neurologist Dr William Camu, head of the national ALS centre of excellence at Montpellier University Hospital and author of the study. He also said that the lake had been affected by the local timber industry and heavy metals.