Environment a chief suspect in mystery neurological disease found only in N.B.

Doctors in New Brunswick are being told to be on the lookout for symptoms of an unknown neurological disease that appears to be a new condition found only in the province and is believed to be linked to environmental causes.

At a public health update on COVID-19 Thursday, Dr. Jennifer Russell, the province's chief medical officer of health, fielded a number of questions about the mystery disease that was identified in 2020 as a cluster, with a single case retroactively identified as far back as 2015.

In an internal memo obtained by Radio-Canada, sent on March 5 by the office of the chief medical officer of health to the New Brunswick Medical Society and to associations of doctors and nurses, the department highlighted a cluster of 42 cases of a progressive neurological syndrome of unknown origin.

Symptoms similar to Creutzfeldt-Jakob disease

The disease has symptoms similar to those of the rare and fatal Creutzfeldt-Jakob disease, but "testing so far has ruled out known prion diseases," the memo stated.

The first case of the disease was retroactively identified in 2015. Three years later, in 2019, 11 additional cases were discovered, with 24 more cases discovered in 2020 and another six in 2021. Five people have died.

• New Brunswick monitoring more than 40 cases of unknown neurological disease

The symptoms are similar to those of prion diseases, which include Creutzfeldt-Jakob disease and some of its variants, including mad cow disease, or bovine spongiform encephalopathy (BSE).

However, despite many similarities, tests for Creutzfeldt-Jakob disease have so far ruled out known prion diseases, the March 5 public health memo states.

Scientists are currently looking into the possibility that this is a new variant of a prion disease — or a new disease entirely.

On Thursday, Russell confirmed it is "most likely a new disease," and noted "we haven't seen this anywhere else" in Canada.

The cases have been reported to Health Canada's Creutzfeldt-Jakob disease surveillance system, which determined that the rising number of cases should now be considered a cluster, Russell said.

At that point, she said, the March 5 memo was sent out to the province's health-care professionals.

Doctors suspect environmental link

According to preliminary data from a research group on the subject, headed by neurologist Alier Marrero of Moncton's Dr. Georges-L.-Dumont University Hospital Centre, the disease is not genetic.

"We don't know yet where this is coming from," but the leading hypothesis so far is that it's environmental, Marrero said in an interview with CBC News on Thursday.

"We believe it is acquired from exposure to something in the environment ... either food, water … toxins."

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Over the course of the six years since the disease first appeared in New Brunswick, case numbers have grown steadily and "clustered" in the Moncton and Acadian Peninsula areas of the province. 

"We have seen clustering of cases in some areas and we don't know why," Marrero said. 

According to the Public Health memo, the median age of the cases is 59 years, although female cases tend to be younger, with an average age of 54. Cases are distributed equally among men and women, the memo said. 

The symptoms of the disease are typically not very specific in the initial stages.

"It's usually behavioural changes … for instance, an excess of anxiety, a little bit of irritability, unexplained pains in the limbs, muscle spasms, insomnia," Marrero said.

As the disease progresses over a course of 18 to 36 months, loss of balance and co-ordination have been observed, and "sometimes patients have abnormal and rapidly progressing brain atrophy."

No public health threat

However, Marrero and Russell both stopped short of calling the cases a public health threat. 

"Fear is usually bad advice because it will paralyze us," Marrero said. "We are working very hard to figure this out, so we can stop it, so we can treat it."

He advised that if anyone suspects they have symptoms of the disease, they should report them to their doctor, who will then refer them to the clinic.  

Symptoms that might appear to be related to the disease could actually be caused by another condition, he said. 

"For instance the patient could have multiple sclerosis, they could have Alzheimer's disease ... or some other condition that could be known and treated. So it's important that they get referred and evaluated."

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Russell agreed.

"Right now, it's just about awareness, making sure that physicians are watching for neurological symptoms like this so they can refer them to be assessed," she said.

"We have a lot of work ahead of us in terms of trying to determine the cause."