Horizontal transmission of Piscirickettsia salmonis from the wild sub‐Antarctic notothenioid fish Eleginops maclovinus to rainbow trout (Oncorhynchus mykiss) under experimental conditions

Abstract

Piscirickettsia salmonis is the aetiological agent of piscirickettsiosis, a bacterial disease that affects farmed salmonids, causing high mortalities and significant economic losses in the Chilean salmon farm industry. Given the Chilean native fish species Patagonian blenny, Eleginops maclovinus, lives in the vicinity of salmon farms, it is relevant to clarify the epidemiological role that this species could play in the transmission and/or dissemination of this pathogen. This study aimed to evaluate the bidirectional transmission of P. salmonis between the Patagonian blenny and Oncorhynchus mykiss (rainbow trout), via a cohabitation challenge model. The results of this study demonstrated the transmission of the bacteria from Patagonian blennies to rainbow trout, considering the specific mortality in cohabitant rainbow trout, reaching 46%: the necropsy of these specimens, evidencing the characteristic pathological lesions of the disease and the positive results of the qPCR analysis for P. salmonis, in the same individuals. In contrast, no mortalities of Patagonian blenny specimens were recorded in the challenged experimental groups. This study is the first report showing the horizontal transmission of P. salmonis from a native non‐salmonid species, such as the Patagonian blenny, to a salmonid species, generating the disease and specific mortality in rainbow trout, using a cohabitation challenge.

Use of antimicrobials in Chilean Salmon farming: Facts, myths and perspectives

“…47 Pathogen-monitoring studies conducted between 2010 and 2018 in southern Chile established that of 7518 specimens of Patagonian blenny (Eleginops maclovinus), only 10.7% (i.e., n = 803) tested positive for P. salmonis through qPCR analysis. 49 Quintanilla et al 49 further reported the ability of P. salmonis to be transmitted from Patagonian blenny to rainbow trout through cohabitation. The susceptible trout presented pathological injuries consistent with piscirickettsiosis, and the inoculated agent was also isolated.…”

“…Of the sampled specimens, only 3.45% tested positive for the detection of P. salmonis DNA 47 . Pathogen‐monitoring studies conducted between 2010 and 2018 in southern Chile established that of 7518 specimens of Patagonian blenny ( Eleginops maclovinus ), only 10.7% (i.e., n = 803) tested positive for P. salmonis through qPCR analysis 49 . Quintanilla et al 49 further reported the ability of P. salmonis to be transmitted from Patagonian blenny to rainbow trout through cohabitation.…”