Lotz, J.M., Ogle, J.T.
Abstract:
Taura Syndrome (TS) is the most important disease of farmed
penaeid shrimp in the Western Hemisphere and is responsible for
large production losses annually. The syndrome was first recognized
as a distinct disease in Ecuador in 1992 and subsequently it has been
identified in most shrimp farming regions of the Americas. TS is a
rapidly, progressing disease marked by extensive mortalities that
become evident 25-35 days after a shrimp pond is stocked with
shrimp. Elevated death rates last only a matter of days but commonly
reach 25% per day and leave a mere 5 - 25% of the shrimp alive.
Interestingly, the survivors of the mortality epidemics suffer no more
than normal mortality rates over the remainder of the production
cycle. The question remains as to whether the survivors of a TS
outbreak are genetically more resistant to TS virus than were those
animals that succumbed to an infection. If TSV survivors are
genetically more resistant then the offspring of a male and female
survivor would likely, be more resistant to a TSV challenge than
would animals that had not been exposed. To test this hypothesis
Penaeus vannamei that had survived a TSV infection and had been
grown to broodstock size in a commercial setting were acquired and
placed in a biosecure quarantine recirculating maturation facility. The
broodstock animals were held and subjected to screening for TSV
infections by bioassay. Although chronic infections are difficult to
detect most animals tested positive for TSV. Subsequently females
were ablated and reproduction ensued. A total of six mated females
were collected and placed in spawning tanks. All six spawned
fertilized eggs and the larvae were transferred to a quarantine larval
rearing. Four of the six spawns developed to postlarvae. The four
spawns were subjected to three bioassay screenings for TSV and
tested negative each time. In addition, the four spawns were
challenged with TSV and assessed for their susceptibility on two
separate occasions. The first TSV challenge found that three of the
four spawns were somewhat more resistant to TSV than a control
group. The second challenge produced similar results. The study
suggests that TSV is not transmitted vertically from female to
offspring through the oocytes and that offspring of TSV survivors
may be more resistant than offspring of animals not subjected to
infection.
(University of Southern Mississippi, Institute of Marine Sciences,
Gulf Coast Research Laboratory, P.O. Box 7000, Ocean Springs,
Mississippi, USA)