Abstract

Bacterial Kidney Disease (BKD) is a chronic infection caused by Renibacterium salmoninarum (Rs). BKD has been reported affecting wild and farmed salmon in most salmon farming regions worldwide. In Chile, the second largest salmon producer in the world, the prevalence of BKD has been steadily increasing during the last years. In this study, we aimed at characterizing the spatial patterns of the occurrence of the disease in both fresh and salt water farms. From January 2014 to April 2019, we used official surveillance data from broodstock Rs-screening, passive surveillance reports from diagnostic tests for Rs, and data from reported BKD-specific mortality, including all salmon farms. In addition to descriptive epidemiological analysis, we used a Bernoulli model through the scan test to identify local spatio-temporal clusters. The scan test was carried out separately for fresh and salt water farms. The overall proportion of BKD-farms was 70.3%, being those farms randomly distributed throughout the country (Fig. 1). A number of significant spatio-temporal clusters were only identified during the growth-out farming stages (i.e., salt water farms). This extensive study is the first to describe the epidemiology of BKD, which preliminary results indicate that different transmission processes may occur and prevail in fresh water and salt water farms.