1 MARCH 1999
Date: 9 February 1999
From: Fariano Lucio <lucio@www.lrcser.it>
QUESTION:
There are many iodophors available on the market for trout eggs
disinfection.
What about acidity and efficacity against viruses (IPN-IHN)?
What about toxicity to eggs of the different kind of acid used (citric,
phosphoric...)
I am interested in the disinfection during water hardening, just after
fertilisation, and not in the "late" disinfection before hatching.
Lucio Fariano
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COMMENTS 1:
Salmonid eggs can be disinfected and/or water hardened in iodophor
solutions.
Disinfection is best done on either eyed eggs or water-hardened green eggs.
Best results occur when the solution is buffered.
Some suppliers indicate their products are buffered, but I would suggest testing pH anyway. It can be buffered with vinegar or sodium
bicarbonate (baking soda).
Iodophor at 25 ppm for 5 minutes will destroy IPN virus. Free iodine at 0.14 pppm will inactivate 99.9% of IHN virus. It should be noted,
however, that IPN virus has been demonstrated experimentally to be
carried within the egg, and in such case, is not inactivated by surface
disinfection. The majority of evidence indicates that surface disinfection will eliminate IHN virus, as it is not generally considered to be transmitted within the egg.
Kent Hauck <agmain.khauck@state.ut.us>
Fish Pathologist
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COMMENTS 2:
Be careful choosing a iodophore to surface disinfect salmonid eggs.
Many iodophores also have phosphoric acid (eg. IOSAN - used as a tit
dip for dairy cattle, has 16.5% phosphoric acid) which kills eggs!
Use a tamed iodine, such as ovadine, or one that contains less than
0.5% phosphoric acid. Try a dose (with Ovadine, anyway) or 100 ppm
for 10 minutes during the water hardening stage. Be sure to keep the
pH between 6 and 7.5. After 10 minutes carefully rinse the
eggs in new water and lay them down in the incubator.
Paul MacIsaac, M.Sc.
Aquaculture Technician
Nova Scotia Agricultural College
Animal Science Department - Aquaculture Unit
PO Box 550 Truro, NS, CANADA B2N 5E3
phone: (902) 893-6533
fax : (902) 895-6734
pmacisaac@cadmin.nsac.ns.ca