ParviLIfe: The Parvicapsula pseudobranchicola life cycle: how can we avoid or live with Parvicapsulosis?

Parvicapsulose is a disease caused by the parasite Parvicapsula pseudobranchicola, which is a major issue in salmon farming in northern Norway. Recently, outbreaks have also been seen in Iceland. The salmon is infected by waterborne spores called actinospores which are released from a polychaete worm, the parasite's final host. Several project have earlier tried to identify the polychaete final host without success, but recently a potential final host was identified in samples from Iceland by Icelandic researchers. With knowledge of the final host, it is now possible to further study the biology of this parasite with the aim to mitigate the disease in the future.

The main question asked in this project is: Why is the disease parvicapsulosis only seen in specific regions within the parasite's overall geographic distribution, while remaining absent in others? This crucial question serves as the focal point for our efforts to proactively address and mitigate the disease in the future. To unravel this mystery, an in-depth understanding of the life cycle of P. pseudobranchicola is imperative. This includes a comprehensive knowledge of the hosts it can infect, an exploration of the spore’s longevity in the environment, and insights into the geographic distribution, habitat (sediment) preferences, and specific environmental requirements of the final host—pertaining to depth and temperature. Additionally, exploring the existence of distinct genetic variants of the parasite is crucial. Establishing connections between these variants and factors such as virulence, host specificity (both polychaete and fish hosts), geographical distribution, or a combination thereof, is essential. Until now, progress in addressing these inquiries has been impeded by the fact that the final host has been unknown. However, with the current knowledge of the identity of the host, we can start on a quest to unravel these questions, ultimately contributing to effective solutions for mitigating parvicapsulosis.