Over the past year, a cluster of forty-eight cases of a distinct neurodegenerative disease arose in New Brunswick, Canada. The disease runs its course quickly, killing the individual in just a matter of months. In identified cases, there is an even split between women and men, and ages range from as old as 85 to as young as 18 (Murphy, 2021). Symptoms ranged from memory problems and muscle spasms to balance issues, vision deterioration, hallucinations, and extreme weight loss without any other underlying cause. Some individuals also experienced marked changes in behavior and pain in their limbs (Government of New Brunswick, 2021).
Initially, this phenomenon was assumed to be Creutzfeldt-Jakob disease (CJD). Although CJD can be genetic in origin, some cases are iatrogenic, meaning the disease is transmitted surgically via direct contact with brain or nervous system tissue. It can also be contracted by eating meat from cattle infected by bovine spongiform encephalopathy (BSE), colloquially referred to as “mad cow disease”. Both CJD and BSE belong to a family of diseases called transmissible spongiform encephalopathies (TSEs), which are caused by misfolded proteins called prions. The word “spongiform” is used because the brains acquire numerous holes, taking on sponge-like appearances. CJD can present as symptoms of dizziness, loss of coordination, impaired memory and cognition, vision problems, and hallucinations, which is largely consistent with the New Brunswick cases (US Department of Health).
To diagnose CJD or rule out any other diseases, physicians typically conduct spinal fluid tests, looking for specific polypeptide markers in the cerebrospinal fluid. However, upon examining spinal tap results, none of the New Brunswick cases had such proteins. Autopsies of the nine deceased individuals in the cluster also revealed no signs of CJD. Since this discovery, scientists have been searching for the source of the New Brunswick outbreak to no avail. Thus, the disease has been termed NBNSUC (New Brunswick Neurological Syndrome of Unknown Cause).
Substantial evidence has now been accumulated for doctors to reach the consensus that this is a novel condition. While almost all the people studied in the cluster ate seafood like lobster, this is probably trivial and there is no evidence linking the symptoms to any particular food. Now scientists have directed their attention to neurotoxic environmental exposures, which they suspect are the culprit due to the geographical localization of the cases. Eight individuals reported that they may have been exposed to harmful algal blooms (Murphy, 2021). Blue-green algae, or cyanobacteria, are of particular concern, since they are known to produce four types of toxins,and neurotoxins are the rarest. When they do produce neurotoxins, it is often anatoxin-a, but all of them interfere with neuronal functioning at the synapse between nerve cells, causing symptoms like muscular paralysis (Hoff, 2007). However, there is no current evidence indicating the exposures in these cases elicited NBNSUC symptoms.
Twenty-five individuals have also reported industrial exposures in their home or workplace, and twelve said they had possible indirect exposure to herbicides or pesticides. Interestingly, more than half of those surveyed said they regularly spent time gardening in the two years before the onset of their symptoms, and at least two people handled pesticides directly (Murphy, 2021). It would not be surprising if pesticides were to blame, as there is an abundance of literature supporting their neurotoxicity. Many pesticides are not highly selective, so in addition to targeting the nervous systems of organisms that pose a threat to crops, they can have unintentional effects on people. While insecticides target ion channels and have more of an acute, reversible toxicity, other pesticides have been associated with the development of chronic neurodegenerative disorders like Parkinson’s disease (Costa, 2007). However, since there is no concrete evidence to support this hypothesis either, for now, the root of this remains elusive (Government of New Brunswick, 2021).
References
Costa, L. G. (2008). Neurotoxicity of pesticides: A brief review. Frontiers in Bioscience, 13(13), 1240. https://doi.org/10.2741/2758
Government of New Brunswick, C. (2021). New Brunswick cluster of neurological syndrome of unknown cause. Government of New Brunswick, Canada. https://www2.gnb.ca/content/gnb/en/departments/ocmoh/cdc/neuro_cluster.html.
Hoff, B., Thomson, G., & Graham, K. (2007). Neurotoxic cyanobacterium (blue-green alga) toxicosis in Ontario. The Canadian veterinary journal = La revue veterinaire canadienne. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1780230/.
Murphy, J. (2021). Doctors investigate Mystery Brain Disease in Canada. BBC News. Retrieved from https://www.bbc.com/news/world-us-canada-56910393.
U.S. Department of Health and Human Services. (n.d.). Creutzfeldt-Jakob Disease Fact Sheet. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Creutzfeldt-Jakob-Disease-Fact-Sheet.
