Rare contagious cancer found in catfish in Quebec-Vermont lake

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OTTAWA — Peer-reviewed studies published in a prominent scientific journal have identified a rare form of transmissible cancer among catfish in a lake straddling the Canada-U.S. border.

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According to the paper Brown bullhead catfish melanoma represents a novel transmissible cancer, published this week in the journal Nature, anglers began noticing odd lesions on brown bullheads pulled from Lake Memphremagog — a 51-km-long glacial lake located 115 km southeast of Montreal that crosses the Quebec-Vermont border.

“A study determined these raised black lesions to be malignant melanomas, on the basis of histopathological analysis, and observed these lesions in 23-37% of brown bullhead sampled between 2014 and 2017,” read an excerpt from the study.

“Melanomas have been reported from brown bullheads in other bodies of water, but generally at considerably lower incidence.”

Researchers confirm the fish pose no danger to humans and are safe to handle and study.

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Transmissible cancers are rare

As bullheads — found in lakes across eastern North America — are considered indicator species of water quality, researchers suspect the high incidence of cancer in Lake Memphremagog is being caused by local contaminants.

“One hypothesis is that extensive flooding in 2011 from tropical storm Irene led to reduced water quality of the lake due to runoff pollution,” the study stated.

“Monitoring changes to water quality is of great concern to biologists and the public, as this lake is the source of drinking water for more than 175,000 people.”

Transmissible cancers are incredibly rare in nature, normally only found in dogs, Tasmanian devils and certain species of aquatic molluscs.

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The study points out that examinations of the water have yet to find any evidence of any viruses or other microorganisms capable of causing this cancer in infected bullheads, leading researchers to believe it’s the cancer cells themselves responsible for infecting new fish.

“If there is a virus or microbial agent that facilitates tumorigenesis, it was not detectable in our tumour samples,” the study explained.

“Although we cannot rule out a role for conventional pathogens in the original emergence or ecological transmission of this disease, the genomic evidence presented here overwhelmingly supports a transmissible cancer in which the tumour cells themselves act as the infectious entity.”

bpassifiume@postmedia.com
X: @bryanpassifiume

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