Heart and skeletal muscle inflammation (HSMI) disease diagnosed on a British Columbia salmon farm through a longitudinal farm study
A) Non-specific clinical signs and gross lesions which have previously been associated with HSMI, as reported by Kongtorp and colleagues [1,9,11]. Any of the following were included: slow-swimmer, off-feed, ascites (e.g. ascites, hemorrhagic ascites, visceral petechiae, etc.), liver (e.g. enlarged, congested, etc.; excluding “green” and “haemorrhagic”), spleen (e.g. enlarged, congested, etc.), and heart (e.g. enlarged, pericardial effusion, etc.). B) All clinical signs and lesions presented in “A” were further aggregated into one category, called “~HSMI”, and compared to additional lesions and clinical signs observed over the course of the production cycle. The latter were aggregated to include five broad categories for: sea lice, mouth rot disease (MMY; myxobacteriosis), poor performers (PP), central nervous system (CNS; e.g. inflammation in red, hemorrhages in purple), and HSMI-related (from Fig 2A). Percentages of fish sampled showing clinical signs or lesions were calculated from the number of fish collected (moribund or dead) at each sampling event (light grey font color located above the sampling date). C) Weekly mortality counts (provided by the company) summarized based on their general classification. The inset demonstrates weekly mortality for each pen of the farm between October 1st and November 26th, 2013: during that period, one pen had increased mortalities (red line), with two more pens minorly affected (royal blue and charcoal lines), and the company veterinarian had submitted fish samples as part of routine investigation.