Researchers are monitoring a troubling outbreak of a contagious cancer, known as bivalve transmissible neoplasia, among soft-shell clams in Washington’s Puget Sound. Early genetic tests indicate that this cancer likely originated from populations along the Atlantic Coast.
By 2024, over 75% of clams sampled at two sites showed signs of infection, which is concerning for scientists because these clams play a vital role in maintaining coastal habitats and the surrounding communities.
What happened?
The findings were published in a study in PNAS, highlighted by Eco Magazine. This disease is unique because it’s a cancer that spreads from one clam to another through seawater.
The first cases were detected in 2022 from samples taken at Triangle Cove and near Stanwood. Follow-up surveys revealed a rapid escalation in infection rates, with over 75% of clams testing positive by 2024 at both sites.
Genetic investigations indicated that the cancer affecting Puget Sound clams belongs to the same lineage found previously in Atlantic Coast populations, suggesting it has arrived in the Pacific Northwest fairly recently. This outbreak is being regarded as one of the most significant documented occurrences of this type of cancer in the region.
To assess the potential spread, the research team conducted a highly sensitive environmental DNA test on seawater gathered from 51 locations throughout Puget Sound. They identified cancer-related DNA at the infected sites and in the nearby waters, though it wasn’t present across the entire region.
Why does it matter?
An outbreak like this in clam populations could have consequences beyond just the clams themselves. These creatures are crucial for filtering water, recycling nutrients, and supporting both marine food webs and the livelihoods of coastal communities. Such an outbreak adds stress to an already vulnerable ecosystem.
The health of Puget Sound has implications for biodiversity, recreational activities, and shellfish resources that are important to many residents of Washington. If diseases can transmit more easily between regions, it could complicate efforts to protect marine life and restore coastal habitats.
This situation might also provide insights into why some species are less susceptible to such diseases. The soft-shell clams in the area, which include hybrids of Mya arenaria and Mya japonica, suggest that the Japanese species might be more resilient to infection. This could yield clues regarding how wild populations adapt to emerging disease threats.
What are people saying?
Dr. Michael Metzger, a senior author and associate investigator at the Pacific Northwest Research Institute, expressed surprise at the level of transmissible cancer spreading among clams in the Pacific Northwest.
He continued, indicating that the scale of this outbreak is significant for understanding the emergence and spread of these rare cancers in wild populations.
Metzger also remarked on the innovative monitoring method, saying it provides researchers with a valuable tool to track the spread of transmissible cancers in marine ecosystems, which could aid in detecting emerging outbreaks before they escalate.
