Action of Alkaline Acriflavine Solution on Bacterium salmonicida and Trout Eggs. ∗

Abstract

Trout furunculosis is a costly, widespread, epizootic bacteremia, that annually destroys millions of salmon and trout. 1 The disease occurs in trout hatcheries and rivers in at least 8 European countries, in Canada, and in more than one-fourth of the United States. Trout furunculosis is caused by Bacterium salmonicida Lehmann and Neumann, a gram-negative non-spore-forming rod which shows deeply-staining, bipolar bodies; the taxomic position of this bacterium has not been determined.

Among the agencies by which furunculosis may be disseminated are trout ova, which in practical fish culture are freely transported from contaminated hatcheries and spawning beds to clean hatcheries. In fish hatcheries, eggs are usually incubated in headwaters; and thus may be a source of infection to fish downstream. The interior of living trout eggs is believed to be bacteriologically sterile. 2 , 3 Only the dead eggs and the exterior of living ones can be considered as sources of infection. The former may readily be removed manually. If, therefore, the exterior of the living ova can be disinfected, eggs may be placed in headwaters in hatcheries, without danger to fish downstream.

Blake⁴ compared a number of disinfectants as to their toxicity for living trout ova and Bact. salmonicida. She recommended a 20-min dip in a solution of 500 parts per million (p.p.m,) neutral acriflavine (2,8-diamino 10 methyl acridinium chloride) as an effective disinfecting treatment which was harmless to trout eggs and lethal for Bact. salmonicida. Browning et al.,⁵ Michaelis and Hayashi,⁶ and Eggerth,⁷ however, show that the bactericidal action of acriflavine is greatly reduced in neutral and acid solution. Gee and Sarles recently compared the action of 19 disinfectants as to their toxicity for trout eggs and to Bact.