Crayfish plague (Aphanomyces astaci)

The Norwegian Veterinary Institute (NVI) conducts crayfish plague surveillance in control areas, combat zones and risk areas.

The purpose of the program is to monitor the infection pressure and infection development in control areas and combat zones for Aphanomyces astaci, and to substantiate disease freedom and/or provide an early warning of possible infection spread in to risk areas


In 2018, A. astaci spread upstream in the Mosse watercourse while no spread was observed in any of the other monitored areas.

  • In the control zone of the Halden watercourse, A. astaci eDNA was only detected in the southern part of Lake Rødenessjøen. Here, the known presence of signal crayfish was confirmed by eDNA detection. No sign of crayfish plague was observed in the northern part of Lake Rødenessjøen (Kroksund) up to the control zone border at Fosserdam. This result was supported by positive detections of noble crayfish eDNA in all water samples from River Hølandselva and upstream. All water samples in this risk area were negative for A. astaci and signal crayfish, while most samples were positive for noble crayfish eDNA.
  • In the Mosse watercourse, no eDNA of A. astaci or signal crayfish was detected. However, one dead crayfish found in Lake Langen was positive for A. astaci, demonstrating that crayfish plague has spread into Lake Våg and Lake Langen. Noble crayfish eDNA was detected at the inlet of Lake Langen.
  • In the Glomma watercourse, no sign of crayfish plague was found, and the samples were negative for all screened targets.
  • In Eidskog municipality, no samples were positive for either signal crayfish or A. astaci, while several were positive for noble crayfish eDNA in River Vrangselva and River Finnsrudelva.

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