how to prevent
the vertical transmission of white spot virus?
From: arb@net.sa
To: shrimp@yahoogroups.com
Date: 04 February 2001
Question:
We all know that White Spot Virus (SEMBV) is
transmitted by vertical and horizontal transmission. How to prevent the
vertical transmission of White Spot Virus? Will washing the egg with 100%
Foramen prevent the vertical
transmission of White Spot Virus from egg to nauplii? Is there any other
method to prevent the vertical transmission of White Spot Virus?
A. Kumaresan
National Prawn Company
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COMMENTS 1:
Does WSSV or SEMBV have vertical transmission? I have
heard that WSSV could be attached to the outside of the egg when brooders
spawn in a heavy WSSV charged environment, and could be disinfected with any
product that applied in a 150 ppm base of Iode. This kind of transmission is
called "per ovum" and isn´t a real vertical transmission.
On the other hand, Lo et al. (1996, 1997) demonstrate that ovarian
cells could be affected by white spot but the viability of the cells were
low and die in the few following hours, or have no fertility.
Vertical transmission can be prevented by using SPF brooders, if you want to
be aseptical.
There are no chemical treatments to prevent vertical transmission, less if a
virus is the infecting organism. Iodine based products disinfect externally
eggs only. Formalin is used to prevent molts, fungus, protozoan and
filamentous algae.
Ac. Luis Alejandro Daqui, MSc Candidate
Molecular Biology Deparment
Fundación CENAIM-ESPOL
ESPOL, Campus Prosperina
P.O. Box 09-01-4519
Guayaquil, Guayas, ECUADOR
Phone: 593-4-916118, 916119, ext. 211
Fax: 593-4-916120
E-mail: ldaqui@cenaim.espol.edu.ec
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COMMENTS 2:
Distinction is made between true vertical transmission and "per ovum". Which of the major viral diseases are true vertical transmission? Which of those don't kill the embryo?
How the problems with these virus are handled depends
upon the answers to these questions. I understand that there are some
fish virus that are true vertical and don't kill the embryo, which makes
them very hard to stop.
Dallas E. Weaver, Ph.D.
E-mail: deweaver@gte.net
***************
COMMENTS 3 :
IHHNV is the unique virus that has real vertical
transmission and doesn’t kill the embryo. (Shrimp Diseases CD, Victoria
Alday & Tim Flegel, 1999). Another virus that affects shrimp has
horizontal transmission. For white spot the vertical transmission has not
been confirmed, because nobody has detected the virus inside the ovum.
In my personal viewpoint the unique strategy to these
viruses is to get SPF brooders to produce virus-free fry. If it is not
possible, I suggest to work with surviving shrimp and to follow a very hard
selection process, producing fry resistant to the virus. The second part
takes time and is an economical effort but if in no alternative works, it is
the last strategy.
Ac. Luis Alejandro Daqui,
MSc Candidate
E-mail: ldaqui@cenaim.espol.edu.ec