New microsporidian parasite identified in Atlantic sardines by Spanish researchers

Scientists from the University of Navarra have documented a previously unknown microsporidian parasite of the genus Glugea infecting the common sardine (Sardina pilchardus). The discovery arose after a distributor found white spherical structures, 5–20 mm in size, inside the visceral cavity of several Atlantic sardines during routine inspection. The research team—Enrique Baquero, Rafael Jordana and Gabriel Reina—used morphological analysis, electron microscopy and genetic sequencing to confirm that the organism does not match any described microsporidian species.

The parasite poses no known risk to human health, but its identification creates a new reference for monitoring emerging marine diseases. Spain’s Atlantic sardine fishery, especially in Galicia and Andalusia, is regulated with a total allowable catch of 16.8 million kg for 2026, supporting ports, markets and processing industries. The study, initiated in 2018‑19, was delayed by the COVID‑19 pandemic and has now been published, providing a genetic profile that will aid future surveillance.

"Nos dijeron que tenían unas sardinas con una cosa muy rara y querían saber qué era," recalled lead researcher Enrique Baquero.