title: Experimental infection of Pacific white shrimp Litopenaeus vannamei with Necrotizing Heptopancreatitis (NHP) bacterium by per os exposure.
abstract: Necrotizing Hepatopancreatitis Bacterium (NHPB), which causes Necrotizing Hepatopancreatitis, was successfully transmitted in individually isolated Kona stock Litopenaeus vannamei through per os exposure. Animals (140) were individually exposed orally to a 0.05 g piece of an NHPB-infected hepatopancreas and 120 control animals were each exposed to a 0.05 g piece of NHPB-negative hepatopancreas. Shrimp were maintained in Sterilite containers with approximately 41 of artificial seawater at 30 per thousand salinity and 30 degrees C for 60 d. Mortality of infected shrimp was observed from Day 16 to Day 51 post-exposure. Infected animals sustained reduced feeding activity and displayed empty guts. Some infected animals developed a pale hepatopancreas noticeable through the carapace. Survival probabilities fit a Weibull distribution and parametric survival analysis revealed lowered survival due to NHPB infection. Median survival time of NHPB-infected animals was 34.5 d. After correcting for background daily mortality in the controls, mean acute daily mortality of NHPB was estimated at 0.09, a value much lower than that estimated for other diseases in Kona stock L. vannamei such as White Spot Syndrome Virus (0.40) and Taura Syndrome Virus (0.30). A chronic, or carrier, state was not demonstrated in NHPB epizootics because all NHPB-positive animals experienced mortality and no animals surviving to 60 d post-exposure were diagnosed NHPB-positive through PCR or histology.
authors.affiliation: Department of Coastal Sciences, The University of Southern Mississippi, Gulf Coast Research Laboratory, PO Box 7000, Ocean Springs, Mississippi 39566-7000, USA.
authors.forename: Amanda G
authors.initials: AG
authors.lastname: Vincent
authors.forename: Verlee M
authors.initials: VM
authors.lastname: Breland
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Lotz
mesh_terms: D000818:Animals; D006090:Gram-Negative Bacteria / Q000472:pathogenicity*; D043143:Hepatopancreas / Q000382:microbiology*; D006652:Histological Techniques / Q000662:veterinary; D010195:Pancreatitis / Q000662:veterinary*; D033561:Penaeidae / Q000382:microbiology*; D016019:Survival Analysis; D013997:Time Factors