Análisis epidemiológico del programa de vigilancia activa de Piscirickettsia salmonis del Servicio Nacional de Pesca y Acuicultura de Chile: -EN- -FR- Analyse épidémiologique du programme de surveillance active de Piscirickettsia salmonis mis en oeuvre par le Service national de la pêche et de l’aquaculture du Chili -ES- Epidemiological analysis of the active surveillance programme for Piscirickettsia salmonis of the National Fisheries and Aquaculture Service of Chile

: Piscirickettsia salmonis is the causative agent of piscirickettsiosis, a disease that causes significant economic losses in salmonid sea farms in Chile. The objective of this study was to determine and describe the geographical distribution, seasonality and time period when P. salmonis was first detected in farms studied under the active surveillance programme for piscirickettsiosis of the National Fisheries and Aquaculture Service of Chile (SERNAPESCA), which was conducted from January 2013 to March 2017. A 0.28% prevalence of piscirickettsiosis was determined in freshwater fish and one of 58.1% in sea farms. The prevalence of P. salmonis was 61.1% in the Aysen region, 59.8% in the Los Lagos region, 5.1% in the Los Rios region and 3.0% in the Magallanes region. In Los Lagos and Aysen, eight clusters of sea farms were identified, in space and time, as having a positive diagnosis of P. salmonis, whereas, in Magallanes, none was identified, confirming the absence of horizontal transmission or spread of the agent in this geographical area. A seasonal variation was found in the monthly prevalence of P. salmonis, with increases in Salmo salar and Oncorhynchus mykiss in summer and autumn, and in Oncorhynchus kisutch in winter, spring and summer. It was determined that the average time required to detect the agent after fish had been transferred to the sea was 105 days (minimum, 7 days; maximum, 351 days), and no differences were found either between regions or species. Thus the results obtained from the active surveillance programme have helped to increase knowledge of the epidemiology of P. salmonis.