Taura Virus Info

[Sean Stevens]

To those interested:
	Don Chen and I have been having extra-group conversations with each 
other and outside parties regarding the possible viruses responsible for 
Taura syndrome (see past postings). One of these conversations may prove 
useful or enlightening to some readers of this group, thus I am posting 
(with permission) some of this info. I hope it is interesting to one or 
all.

(For those not up-to-date, this relates to a relatively recently 
described 'shrimp plague' that originated in the Taura river basin in 
Ecuador a few years ago and has made it's way north to Texas. Along the 
way it has devastated commercial shrimp farms, with death rates up to 
90% in some reports. Because of the economic impact, and the fact that 
the virus responsible is only just now being described I thought some 
people may have been interested in a discussion. In light of all the 
hoopla regarding 'emerging disease' this provides a nonhuman model of a 
deadly potentially viral epidemic that is relatively new to us, and 
could serve both as a warning and a test subject for our responsiveness)

Lotz responses:

(stuff deleted)

This virus is probably a picornovirus (RNA)

> 2.    Has the virus been shown to be specific to P. vannamei and not
> other species?

It will infect other species including P. setiferus

> 3.    For those of you in the Gulf region, what are they going to do
> with the carcasses of these shrimp?  They aren't going to grind them
> up and feed them to other shrimp or other animals are they?

We are working at our lab on Taura Virus particularly relating to its
effect on native species and the effect of size (age) on susceptibility 
of various penaeids. In addition we are working on general epidemiology, 
transmission, and disinfection.


> 4.    Are there any environmental dependencies- ie temperature,
> salinity, etc?
> 

Not known

We have been involved in research on Taura Syndrome since it was first 
4~
recognized as a virus by J. Brock and D. Lightner about a year ago. It 
was originally hypothesized to be the result of toxicity from antifungal 
chemicals used on banana crops in Ecuador but that now appears unlikely.

The virus showed up for the first time in the U.S. on Texas shrimp farms 
this year. The source of the virus for this outbreak is still unknown. 
However, outbreaks of Taura Syndrome have steadily been moving north 
from 
Ecuador, Central America, and Mexico.

We have worked closely with Lightner's group and they are very close to 
developing and testing a gene probe for detection of the virus.

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:: Jeffrey M. Lotz                     Phone (601) 872-4247             
::
:: Gulf Coast Research Lab             Fax   (601) 872-4204             
::
:: P.O. Box 7000                       Internet: jLotz at medea.gp.usm.edu 
::
:: Ocean Springs, MS 39566-7000 USA                                     
::
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::



Don,

The virus is apparently a picornovirus based on its size and RNA 
content. 
It is cytoplasmic, I believe but am not completely sure.

The idea that it is specific to P. vannamei was never the situation. 
However, initial studies my us as well as by Lightner resulted in no 
detectable infection in the northern Gulf of Mexico native shrimp: pink 
P. duaorarum, brown P. aztecu, and white P. setiferus. P. setiferus is 
closely related to P. vannamei. These initial studies were done with 
large >2gm shrimp. No mortality was noted in any other than the P. 
vannamei. The diagnosis of TSV is based exclusively on the demonstration 
of characteristic hypodermal lesions and bioassay with P. vannamei.

Recently we have exposed postlarval (<0.5gm) P. aztecus, P. duorarum, 
and 
P. setiferus to the virus and have observed mortalities and detected
Taura syndrome lesions in P. setiferus but neither mortality nor lesions 
in P. aztecus or P. duorarum. The only other species that has been 
tested 
is P. stylirostris (related to P. setiferus and P. vannamei) and it is 
much less susceptible to mortalities. The P. stylirostris work was done 
by Jim Brock and I don't know whether or not he observed lesions.

Unfortunately there are no continuous cell lines for any crustacean and 
the 
primary cultures have not be successful in providing a medium for the 
culture of any viruses (at least not in penaeid shrimp).

You are probably aware that a number of baculoviruses from penaeid 
shrimp 
have been described but TSV is not one. 

However, an aparently non-occluded baculovirus which is quite nasty has 
recently been described from shrimp culture in Asia. It causes mass 
mortalities in shrimp culture and death in about 3 days. It is probably 
responsible for the recent decline in production in China and now in 
India.

Regards,

Jeff


Thanks to both Don Chen and Jeff Lotz for all the data. Anyone else?

Sean Stevens  The Rockefeller University
stevens at rockvax.rockefeller.edu