Intraovum Infection Caused by Flavobacterium psychrophilum among Eggs from Captive Atlantic Salmon Broodfish

This study indicated that the bacterium Flavobacterium psychrophilum induced an infection within eggs of Atlantic salmon Salmo salar that were held at federal New England restoration facilities. The pathogen, which originated from the Connecticut, Penobscot, Machias, East Machias, Dennys, Narraguagus, and Sheepscot rivers, was obtained from these eggs at concentrations that ranged from 5.0 × 10 2 to 2.5 × 10 8 colony‐forming units per gram of egg, despite successive treatments with povidone iodine (I 2 ). Treatments consisted of 50 mg/L of water for 30 min, then 100 mg/L for 10 min, followed at the eyed egg stage by 100 mg/L for 60 min. Collectively, 63% of the egg lots (77 of 122) obtained from paired matings of these captive broodfish were infected; 39% of these lots contained 10 or fewer infected eggs (60 eggs sampled per lot), and less than 10% of the lots contained more than 20 positive eggs. Consequently, standard iodophor disinfection procedures were ineffective. Eggs were positive from each of the river‐specific captive brood populations during both of the spawning cycles that were studied. I concluded that F. psychrophilum established an intraovum infection that was prevalent among captive brood lots from different New England watersheds.