83.6—Testing requirements.
(a)
A facility can demonstrate freedom from VHS through negative testing results provided by an approved laboratory. Testing must meet the following conditions:
(1)
Be conducted with a sample size that provides for a 95 percent confidence level of detecting a 2 percent prevalence of infection in the facility.
(i)
Facilities with cultured fish of VHS-regulated species which can document a 2-year history of negative testing for VHS virus, can conduct testing at a sampling level to provide a 95 percent confidence level of detecting a 5 percent prevalence of infection in the facility. Such testing must be conducted twice a year, with at least 3 months between tests.
(ii)
Facilities with cultured fish of VHS-regulated species which can document a 4-year history of negative testing for VHS virus can conduct testing at a sampling level to provide a 95 percent confidence level of detecting a 10 percent prevalence of infection in the facility. Such testing must be conducted twice a year, with at least 3 months between tests.
(iii)
Such facilities must be on a secure water source, and document that any VHS-regulated species in the facility that originated in VHS-regulated States or Canadian provinces originate from facilities of the same or higher health status.
(2)
Include virus isolation or other assays authorized by the Administrator, using appropriate cell lines to detect VHS virus, if present. All suspect VHS cytopathic effects must be positively identified as VHS through molecular assays and/or genetic sequencing.
(3)
Use proportional numbers of each VHS-regulated fish species which might be present in the facility.
(4)
Be conducted at water temperatures between 50 and 72 °F, or at other times or under environmental conditions when VHS is most likely to be detected, if present.
(b)
When APHIS adds a new species to the list of VHS-regulated species after a facility has been determined to be free of VHS in accordance with paragraph (a) of this section, the facility must conduct additional testing on fish of the newly listed species, if present in the facility, and the fish must be free of VHS virus for the facility to retain its free status. VHS testing must be conducted on each newly listed species with a sample size that provides for a 95 percent confidence level of detecting a 2 percent prevalence of infection in the facility.
(c)
For VHS-regulated fish maintained on a secure water source, test results will be valid for 6 months from the date of sample collection provided that no fish of a lesser or unknown health status are introduced into the facility. Test results for fish held on a water source that is not a secure water source will be valid for 30 days from the date of sample collection.