Info of PvNV and IMNV

Disease Information: Comparisons between PvNV and IMNV

PvNV, a nodavirus which can cause muscle necrosis in P. vannamei was firstly found in Belize in 2004. The symptoms of PvNV and IMNV infection are quite similar, however the consequences of the infection are far from the same. In order not to mis-judge the seriousness when the abnormal symptoms shown in the pond, carefully sampling and diagnosis are highly recommended.

The table of comparisons is listed below:

	IMNV	PvNV
First appearance	Brazil, 2002	Belize, 2004
Agent	Totivirus	Nodavirus
Symptoms	Focal to extensive white necrotic areas in the striated muscle, especially of the distal abdominal segments and tail fan. Lesions with coagulative muscle necrosis, often with edema. Ectopic lymphoid organ spheroids are often found in the hemocoel and loose connective tissues	White, opaque lesions in tails; Multifocal necrosis and hemocytic fibrosis in the skeletal muscle; Basophilic cytoplasmic inclusions were found in striated muscle, lymphoid organ and connective tissues.
Susceptible species	Originated found in P. vannamei; P. monodon and L. stylirostris can also be infected experimentally	Originated found in P. vannamei; P. monodon can also be infected experimentally
Mortality	20%~60% in P. vannamei; No mortalities were observed in either L. stylirostris or P. monodon experimentally. Acute onset of elevated mortalities, but progresses to a chronic course with persistent low-level mortalities; Poor feed conversion rates and associated production losses.	Associated with the environmental stress. Mortality in laboratory bioassays has not been found.
Diagnostic methods	IQ2000^TM IMNV Detection and Prevention System has been developed and commercialized since October, 2004.	No commercial product currently.

Acknowledgements

We would like to show our appreciation to Dr. Lightner's group for sharing their first-hand research results

Reference

1. Tang KF, Pantoja CR, Poulos BT, Redman RM, Lightner DV.(2005) In situ hybridization demonstrates that Litopenaeus vannamei, L. stylirostris and Penaeus monodon are susceptible to experimental infection with infectious myonecrosis virus (IMNV). Dis Aquat Org 28: 261-265.

2. Tang KF, Pantoja CR, Poulos BT, Redman RM, Lightner DV.(2007) Development of in situ hybridization and RT-PCR assay for the detection of a nodavirus (PvNV) that causes muscle necrosis in Penaeus vannamei. Dis Aquat Org 75: 183-190.

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