Inter-Research > DAO > v61 > n3 > p227-233  
Diseases of Aquatic Organisms

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DAO 61:227-233 (2004)  -  doi:10.3354/dao061227

Experimental infection of Pacific white shrimp Litopenaeus vannamei with Necrotizing Hepto-pancreatitis (NHP) bacterium by per os exposure

Amanda G. Vincent, Verlee M. Breland, Jeffrey M. Lotz*

Department of Coastal Sciences, The University of Southern Mississippi, Gulf Coast Research Laboratory, PO Box 7000, Ocean Springs, Mississippi 39566-7000, USA
*Corresponding author. Email:

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 4 l of artificial seawater at 30‰ salinity and 30°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.

KEY WORDS: Necrotizing Hepatopancreatitis · NHP · Shrimp disease · Shrimp aquaculture

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