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Deadly Cancer Spreads Among West Coast Clams
10 Jul
Summary
- A contagious cancer impacts soft-shelled clams on the West Coast.
- Three-quarters of clams are affected in Washington's Puget Sound.
- The cancer spreads via seawater and poses no human health risk.

Soft-shelled clams along the West Coast are succumbing to a contagious and deadly cancer. This outbreak, first detected in Washington state's Puget Sound in 2022, has severely impacted the clam population in Triangle Cove, affecting three-quarters of individuals there.
The disease, known as bivalve transmissible neoplasia, spreads between marine animals through seawater. While it has no known direct impact on human health and the clams remain safe for consumption, the infections threaten the wider ecosystem.
This cancer, previously found on the East Coast, has now appeared on the West Coast, with genetic analysis linking it to lineages found in Atlantic and Japanese clam species. Scientists are investigating how the cancer arrived in Washington waters, with human-assisted transport being a likely explanation.
The outbreak offers a unique chance for scientists to study how wild clams respond to such diseases. Understanding the transmission of transmissible cancers between regions is considered critical for managing future outbreaks and protecting vulnerable shellfish populations already at risk from pollution and climate change.