Piscirickettsia salmonis

Piscirickettsia salmonis is the bacterial causative agent of piscirickettsiosis, an epizootic disease in salmonid fishes. It has a major impact on salmon populations, with a mortality rate of up to 90% in some species. The type strain, LF-89, is from Chile, but multiple strains exist, and some are more virulent than others. P. salmonis and piscrickettsiosis are present in various geographic regions from Europe to Oceania to South America, but the Chilean salmon farming industry has been particularly hard-hit. Different strategies of controlling the disease and farm-to-farm spread have been the subject of much research, but a significant amount is still unknown.

History

The disease caused by Piscirickettsia salmonis, piscirickettsiosis, was first identified in Chile in 1989 as coho salmon syndrome, although observations of the illness date to at least 1981. P. salmonis was first described in 1992, when it was identified as the causative agent of the disease and classified as a member of the family Rickettsiaceae before it was reclassified as a member of family Piscirickettsiaceae in 2003.

When piscirickettsiosis was first reported in 1989, it was one of the greatest threats to salmon aquaculture in Chile, with some infection coho salmon populations experiencing mortality rates of 90%. Economic loss in 1989 due to the disease was US$10 million; by 1995, the loss was US$49 million. Impacts decreased in the early 2000s due to improved management practices and a shift in farmed populations from highly vulnerable coho salmon to more resistant Atlantic salmon, although the disease was still considered to be one of the largest problems facing the Chilean salmon farming industry.