* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Marine Shrimp Conference
Eradication of infectious diseases wikipedia , lookup
Leptospirosis wikipedia , lookup
Traveler's diarrhea wikipedia , lookup
Cross-species transmission wikipedia , lookup
Oesophagostomum wikipedia , lookup
Sarcocystis wikipedia , lookup
Schistosomiasis wikipedia , lookup
Human cytomegalovirus wikipedia , lookup
Gastroenteritis wikipedia , lookup
Ebola virus disease wikipedia , lookup
African trypanosomiasis wikipedia , lookup
Sexually transmitted infection wikipedia , lookup
Hepatitis C wikipedia , lookup
Neonatal infection wikipedia , lookup
Middle East respiratory syndrome wikipedia , lookup
West Nile fever wikipedia , lookup
Influenza A virus wikipedia , lookup
Hospital-acquired infection wikipedia , lookup
Marburg virus disease wikipedia , lookup
Henipavirus wikipedia , lookup
Orthohantavirus wikipedia , lookup
Hepatitis B wikipedia , lookup
Center of Excellence for Shrimp Molecular Biology and Biotechnology Problematic transfer of viruses amongst penaeid shrimp Tim Flegel Centex Shrimp, Chalermprakiat Building, Fac. Science Mahidol University, Rama 6 Road, Bangkok 10400, Thailand National Center for Genetic Engineering and Biotechnology Overall viewpoint Live aquatic animals present far the highest risk for viral disease transfer All well studied cases of shrimp viral disease transfer have occurred by this route Most cases have involved shrimp for aquaculture No proven case of transfer by importation and use of fresh frozen shrimp for human consumption Disease imported with crustaceans in ballast and on hulls has not been properly assessed Intentional import of live shrimp All major cases of shrimp viral transfer have occurred by importation of brooders and PL This includes importation of exotic species and resident species from other countries Three well documented cases: – Infectious hypodermal and hematopoeitic necrosis virus (IHHNV) from Asia to the Americas – White spot syndrome virus (WSSV) initially from China to Japan but then to Asia and the Americas – Taura syndrome virus (TSV) initially around the Americas but then to Taiwan and Asia Most exotic introductions intentional Cause of import No. of % records Known and intentional Aquaculture Fisheries Ornamental Research Oher reasons Total intentional 1386 39 299 8 263 7 104 3 272 8 2324 65 Known but unintentional Angling/sport Diffused from other countries Accidental Bait Total unintentional Unknown 283 8 139 4 267 8 14 >1 703 20 552 15 Source: FAO website Importations by group Species group Fishes Molluscs Crustaceans Algae and plants Other invertebrates Other vertebrates Source: FAO website # records % 2574 82 294 9 191 6 35 1 29 1 18 1 Shrimp viruses a particular danger Viruses alone are responsible for the most severe losses in shrimp aquaculture We know that shrimp react to viruses in a way different from vertebrates (from fish to man) Shrimp and other crustaceans are characterized by persistent viral infections These infections often produce no gross signs of disease and no mortality Many of these “hidden” or “cryptic” viruses are still unknown Dual and multiple viral infections Dual, triple and multiple viral infections are often seen in shrimp, but rarely reported We rarely examine “healthy” shrimp This applies also to other crustaceans and arthropods such as insects Viruses with the same name may be quite different genetically (e.g., HPV variants) A cryptic virus tolerated in one host or location may not be tolerated in another host or location Crustaceans a particular threat Infection status # Shrimp % Total 14 5.9 Uninfected 223 94.1 Infected 237 100.0 Total tested 50 21.1 Single infections MBV 8 3.4 HPV 13 5.5 WSSV 19 8.0 IHHNV 10 4.2 69 29.1 Dual infections 80 33.8 Triple infections 24 10.1 Quadruple 173 73.0 Dual to quadruple Grossly healthy shrimp A study of 6 ponds in Thailand (Flegel et al. 2001) Triple viral infection Example of dangerous exchanges P. monodon YHV WSSV IHHNV MOV? LOVV? TSV? BP? Reo-like virus? P. vannamei LOVV-like virus in P. monodon Dr. Lightner found this in LO of P. monodon brooders from the Andaman Sea in late 2002 Virions 25 nm Test with P. monodon Aj. Boonsirm took slow growing P. monodon Homogenized LO and filtered out bacteria Injected into SPF P. monodon and cultured with un-injected control shrimp Result after 2 months – Un-injected shrimp………. 8 g – LO injected shrimp………. 4 g LO samples sent for microscopy Light microscopy of LO Electron microscopy of LO Virions 25 nm Probe urgently needed For a non-destructive detection method to screen broodstock and PL To identify possible carriers We now have a tentative probe that gives positive results with test shrimp and negative with control shrimp Its sensitivity, specificity and applicability are being tested Risks of viral transfer SOURCE ASSESSED RECOMMENDATION RISK Live stocks Very high No import from infected areas Green shrimp High No import from for bait infected areas Green shrimp Low Proper disposal of for processing waste and water Green shrimp Very low Free trade for human food (acceptable) Cooked shrimp No risk Free trade Shrimp head meal Ballast water No risk Free trade ? Ballast water exchange Important lessons Crustaceans can carry unknown viral pathogens as innocuous, active infections Many carriers (including PL) are grossly normal, so PCR needed for detection These viruses may be deadly to other species or the same species at distant locations Greater geographical separation = greater danger By far, the most common route of transfer is with live broodstock or PL for aquaculture No proven transfer from processing plants or from shrimp for human consumption Conclusions Careless movement of live stocks has been the cause of most shrimp disease transfers Live introductions from ballast water and hull fouling may also be a source of disease The evidence in hand suggests that frozen shrimp for human consumption does not pose a significant transfer risk Any risks from frozen shrimp can be decreased substantially by simple risk reduction measures PCR is recommended for screening live shrimp but is inappropriate for frozen shrimp