title: Determination of minimal concentration of Piscirickettsia salmonis in water columns to establish a fallowing period in salmon farms.
abstract: Abstract A highly sensitive real-time PCR procedure to detect and quantify the number of Pisciricketsia salmonis units in seawater samples from affected farm sites has been developed. The purpose was to determine a fallowing period that would allow safe restocking of the target farm with new fish. Bacterial load was determined in water samples by comparing the obtained amplification values against a standard curve generated by the amplification of known concentrations of the ITS-ribosomal component of P. salmonis DNA, cloned in a suitable vector. The standard curve was linear over the range of 10(1)-10(10) log units. Target samples were taken every 10 days over a 40-day period, at 5 m depth and at the surface. In a highly affected area of southern Chile, the number of bacterial units in farm water decreased to zero at day 50. Therefore, a fallowing period of 50 days post-removal of cages of affected fish appears to be appropriate before restocking. This procedure could be adapted to control disease problems because of other pathogens in fish farm waters.
authors.affiliation: Laboratorio de Genética e Inmunología Molecular, Instituto de Biología, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile. smarshal@ucv.cl
authors.forename: J
authors.initials: J
authors.lastname: Olivares
authors.forename: S H
authors.initials: SH
authors.lastname: Marshall
mesh_terms: D000818:Animals; D004269:DNA, Bacterial / Q000032:analysis; D005393:Fish Diseases / Q000382:microbiology*; D005398:Fisheries; D053522:Piscirickettsia / Q000502:physiology*; D044225:Piscirickettsiaceae Infections / Q000382:microbiology / Q000662:veterinary*; D012015:Reference Standards; D012474:Salmon; D012623:Seawater / Q000737:chemistry / Q000382:microbiology*; D013997:Time Factors; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial