Report on General Surveillance in Pacific oysters and Manila clams in British Columbia (Fall 2006-Spring 2009)

Executive Summary

In fall 2006, the Canadian Food Inspection Agency (CFIA) implemented a two-year survey of Pacific oyster (Crassostrea gigas) and Manila clam (Venerupis philippinarum) in British Columbia for diseases of trade significance in shellfish. The list of diseases included:

  • Marteilia refringens
  • Perkinsus marinus
  • Perkinsus olseni
  • Bonamia ostreae
  • Bonamia exitiosa
  • Bonamia (= Mikrocytos) roughleyi
  • Marteilia sydneyi
  • Marteilioides chungmuensis
  • Vibrio tapetis
  • Haplosporidium nelsoni (MSX)
  • Haplosporidium costale (SSO)

The primary objective of the survey was to determine the status of specific shellfish diseases that affect Manila clams and Pacific oysters in British Columbia. To do so, the CFIA used a sampling plan and testing methodology that meets international standards.

The surveillance plan was developed in close collaboration with the industry, the British Columbia Shellfish Growers Association (BCSGA), Fisheries and Oceans Canada (DFO), and the British Columbia Ministry of Agriculture and Land. (BCMAL)

Between the fall of 2006 and the spring of 2009, more than 4,400 shellfish were tested: including 2,035 Pacific oysters and 2,354 Manila clams. The animals, both wild1 and cultured (farmed), originated from the top-harvested DFO fisheries management areas for these species.

All Manila clams tested negative for the 11 targeted diseases.

In the Pacific cultured oysters, two were detected with Haplosporidium nelsoni (MSX) from one DFO area. Haplosporidium costale (SSO) was also detected in two cultured Pacific oysters from two other DFO areas with clinical signs observed in both specimens. In addition, there were 16 confirmed cases of M. mackini however, this disease is endemic to coastal British Columbia.

As per the survey design, negative test results indicate with 95% certainty that if any one of the 11 targeted disease agents were present in these two commercially valuable shellfish populations, less than 2% of the animals would be infected. Therefore, based on the results, we are reasonably certain that both species from Southern British Columbia are free of the following diseases

  • Marteilia refringens
  • Perkinsus marinus
  • Perkinsus olseni
  • Bonamia ostreae2
  • Bonamia exitiosa
  • Bonamia (= Mikrocytos) roughleyi
  • Marteilia sydneyi
  • Marteilioides chungmuensis
  • Vibrio tapetis

1. For the purpose of this project, wild animals, for both species, are defined as animals not found on an aquaculture lease.

2. Note that Bonamia ostreae was detected in European flat oysters from two locations of coastal B.C. in 2004 and 2005.

A copy of the complete report is available upon request.