Limits...
A novel integrase-containing element may interact with Laem-Singh virus (LSNV) to cause slow growth in giant tiger shrimp.

Panphut W, Senapin S, Sriurairatana S, Withyachumnarnkul B, Flegel TW - BMC Vet. Res. (2011)

Bottom Line: ICE was never found in the absence of LSNV although LSNV was sometimes found in normal shrimp in the absence of ICE.The results suggest that ICE and LSNV may act together as component causes of MSGS, but this cannot be proven conclusively without single and combined bioassays using purified preparations of both ICE and LSNV.Despite this ambiguity, it is recommended in the interim that ICE be added to the agents such as LSNV already listed for exclusion from domesticated stocks of the black tiger shrimp.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centex Shrimp, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.

ABSTRACT

Background: From 2001-2003 monodon slow growth syndrome (MSGS) caused severe economic losses for Thai shrimp farmers who cultivated the native, giant tiger shrimp, and this led them to adopt exotic stocks of the domesticated whiteleg shrimp as the species of cultivation choice, despite the higher value of giant tiger shrimp. In 2008, newly discovered Laem-Singh virus (LSNV) was proposed as a necessary but insufficient cause of MSGS, and this stimulated the search for the additional component cause(s) of MSGS in the hope that discovery would lead to preventative measures that could revive cultivation of the higher value native shrimp species.

Results: Using a universal shotgun cloning protocol, a novel RNA, integrase-containing element (ICE) was found in giant tiger shrimp from MSGS ponds (GenBank accession number FJ498866). In situ hybridization probes and RT-PCR tests revealed that ICE and Laem-Singh virus (LSNV) occurred together in lymphoid organs (LO) of shrimp from MSGS ponds but not in shrimp from normal ponds. Tissue homogenates of shrimp from MSGS ponds yielded a fraction that gave positive RT-PCR reactions for both ICE and LSNV and showed viral-like particles by transmission electron microscopy (TEM). Bioassays of this fraction with juvenile giant tiger shrimp resulted in retarded growth with gross signs of MSGS, and in situ hybridization assays revealed ICE and LSNV together in LO, eyes and gills. Viral-like particles similar to those seen in tissue extracts from natural infections were also seen by TEM.

Conclusions: ICE and LSNV were found together only in shrimp from MSGS ponds and only in shrimp showing gross signs of MSGS after injection with a preparation containing ICE and LSNV. ICE was never found in the absence of LSNV although LSNV was sometimes found in normal shrimp in the absence of ICE. The results suggest that ICE and LSNV may act together as component causes of MSGS, but this cannot be proven conclusively without single and combined bioassays using purified preparations of both ICE and LSNV. Despite this ambiguity, it is recommended in the interim that ICE be added to the agents such as LSNV already listed for exclusion from domesticated stocks of the black tiger shrimp.

Show MeSH

Related in: MedlinePlus

Gross signs of MSGS in bioassay shrimp. Comparison at the same scale of gross morphology of control and ICE-injected P. monodon from the second challenge test. The ICE-injected shrimp are generally smaller and darker colored than the control shrimp.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3117699&req=5

Figure 7: Gross signs of MSGS in bioassay shrimp. Comparison at the same scale of gross morphology of control and ICE-injected P. monodon from the second challenge test. The ICE-injected shrimp are generally smaller and darker colored than the control shrimp.

Mentions: At the end of 60 days in the second challenge experiment, there was again no significant difference in survival between the test (75.0%) and control (78.6%) groups. As with the first test, there was a tendency for abnormally dark coloration and brittle antennae in the test but not the control group (Figure 7). Also, one-step or nested RT-PCR (Table 3) revealed that all of the test shrimp and many of the control shrimp were positive for LSNV by nested RT-PCR, while only the test shrimp were positive for ICE by either one-step or nested RT-PCR (as in the first challenge experiment). However, in the second challenge experiment, the test group had significantly lower mean weight (p = 0.001), weight gain (p = 0.032), length (p = 0.001) and length gain (p = 0.001) than the control group (Table 4).


A novel integrase-containing element may interact with Laem-Singh virus (LSNV) to cause slow growth in giant tiger shrimp.

Panphut W, Senapin S, Sriurairatana S, Withyachumnarnkul B, Flegel TW - BMC Vet. Res. (2011)

Gross signs of MSGS in bioassay shrimp. Comparison at the same scale of gross morphology of control and ICE-injected P. monodon from the second challenge test. The ICE-injected shrimp are generally smaller and darker colored than the control shrimp.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117699&req=5

Figure 7: Gross signs of MSGS in bioassay shrimp. Comparison at the same scale of gross morphology of control and ICE-injected P. monodon from the second challenge test. The ICE-injected shrimp are generally smaller and darker colored than the control shrimp.
Mentions: At the end of 60 days in the second challenge experiment, there was again no significant difference in survival between the test (75.0%) and control (78.6%) groups. As with the first test, there was a tendency for abnormally dark coloration and brittle antennae in the test but not the control group (Figure 7). Also, one-step or nested RT-PCR (Table 3) revealed that all of the test shrimp and many of the control shrimp were positive for LSNV by nested RT-PCR, while only the test shrimp were positive for ICE by either one-step or nested RT-PCR (as in the first challenge experiment). However, in the second challenge experiment, the test group had significantly lower mean weight (p = 0.001), weight gain (p = 0.032), length (p = 0.001) and length gain (p = 0.001) than the control group (Table 4).

Bottom Line: ICE was never found in the absence of LSNV although LSNV was sometimes found in normal shrimp in the absence of ICE.The results suggest that ICE and LSNV may act together as component causes of MSGS, but this cannot be proven conclusively without single and combined bioassays using purified preparations of both ICE and LSNV.Despite this ambiguity, it is recommended in the interim that ICE be added to the agents such as LSNV already listed for exclusion from domesticated stocks of the black tiger shrimp.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centex Shrimp, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.

ABSTRACT

Background: From 2001-2003 monodon slow growth syndrome (MSGS) caused severe economic losses for Thai shrimp farmers who cultivated the native, giant tiger shrimp, and this led them to adopt exotic stocks of the domesticated whiteleg shrimp as the species of cultivation choice, despite the higher value of giant tiger shrimp. In 2008, newly discovered Laem-Singh virus (LSNV) was proposed as a necessary but insufficient cause of MSGS, and this stimulated the search for the additional component cause(s) of MSGS in the hope that discovery would lead to preventative measures that could revive cultivation of the higher value native shrimp species.

Results: Using a universal shotgun cloning protocol, a novel RNA, integrase-containing element (ICE) was found in giant tiger shrimp from MSGS ponds (GenBank accession number FJ498866). In situ hybridization probes and RT-PCR tests revealed that ICE and Laem-Singh virus (LSNV) occurred together in lymphoid organs (LO) of shrimp from MSGS ponds but not in shrimp from normal ponds. Tissue homogenates of shrimp from MSGS ponds yielded a fraction that gave positive RT-PCR reactions for both ICE and LSNV and showed viral-like particles by transmission electron microscopy (TEM). Bioassays of this fraction with juvenile giant tiger shrimp resulted in retarded growth with gross signs of MSGS, and in situ hybridization assays revealed ICE and LSNV together in LO, eyes and gills. Viral-like particles similar to those seen in tissue extracts from natural infections were also seen by TEM.

Conclusions: ICE and LSNV were found together only in shrimp from MSGS ponds and only in shrimp showing gross signs of MSGS after injection with a preparation containing ICE and LSNV. ICE was never found in the absence of LSNV although LSNV was sometimes found in normal shrimp in the absence of ICE. The results suggest that ICE and LSNV may act together as component causes of MSGS, but this cannot be proven conclusively without single and combined bioassays using purified preparations of both ICE and LSNV. Despite this ambiguity, it is recommended in the interim that ICE be added to the agents such as LSNV already listed for exclusion from domesticated stocks of the black tiger shrimp.

Show MeSH
Related in: MedlinePlus