INFECTION OF SEA LAMPREY WITH AN UNUSUAL STRAIN OF AEROMONAS SALMONICIDA

Abstract The invasion of the Laurentian Great Lakes by the fish-parasitic sea lamprey has led to catastrophic consequences, including the potential introduction of fish pathogens. Aeromonas salmonicida is a bacterial fish pathogen that causes devastating losses worldwide. Currently, there are five accepted subspecies of Aeromonas salmonicida: A. salmonicida subsp. salmonicida, masoucida, smithia, achromogenes, and pectinolytica. We discuss the discovery of an isolate of A. salmonicida that is pathogenic to rainbow trout (Oncorhynchus mykiss) and exhibits unique phenotypic and molecular characteristics. We examined 181 adult sea lamprey (Petromyzon marinus) from the Humber River (Lake Ontario watershed) and 162 adult sea lamprey from Duffins Creek (Lake Ontario watershed) during the spring seasons of 2005–11. Among those, 4/343 (1.2%) sea lamprey were culture positive for A. salmonicida, whereby biochemical and molecular studies identified three of the isolates as A. salmonicida subsp. salmonicida. The rem...