Reappraisal of
the federal fish health recommendation for disinfecting eggs of Atlantic
salmon in iodophor
R.C. Cipriano, B.M. Novak, D.E. Flint, D.C.
Cutting-2001
Journal of Aquatic Animal Health, 13(4): 320-327
(from Current Contents)
Abstract:
The U.S. Fish and Wildlife Service federal protocol
for dual disinfection of fish eggs in 50 mg/L iodine solution for 30 min
followed by a secondary disinfection in 100 mg/L iodine for 10 min was
investigated during six spawning cycles of Atlantic salmon Salmo salar held
at the Richard Cronin National Salmon Station (Sunderland, Massachusetts).
This population of salmon had undergone an epizootic of furunculosis, and
the surviving fish maintained a persistent infection of Aeromonas
salmonicida throughout the course of study. Eggs from 20 individual paired
matings of salmon were obtained annually during the first 2 weeks of
November in each spawning cycle from 1995 through 2000 except for 1999, when
fertilized eggs from 35 pairs of salmon were examined. Aeromonas salmonicida
was isolated from 19 of the total 135 groups of fertilized eggs investigated
during this study. In those cases, all isolations of the pathogen were made
only in fertilized eggs that had not yet undergone disinfection in iodophor.
In contrast to the results produced in the field, in vitro assays showed
that A. salmonicida was not completely killed when initial concentrations of
the bacterium ranged between 1.0 x 10(7) and 1.2 x 10(8) colony forming
units [CFU]/mL. However, even when bacterial concentrations exceeded 1.0 x
10(7) CFU/mL, no A. salmonicida remained viable in eggs treated first with
50 mg/L iodine for 30 min and then with 100 mg/L iodine for 10 min, as
prescribed in federal policy. Results of the current analysis also provided
further evidence that A. salmonicida is not transmitted vertically through
intra-ovum infection.
(US Geol Survey, Natl Fish Hlth Res Lab, 1700 Leetown
Rd, Kearneysville, WV 25430, USA, e-mail: rocco_cipriano@usgs.gov)