Infectious myonecrosis (IMN), caused by the Infectious Myonecrosis Virus (IMNV), is a rapidly expanding viral disease that severely impacts whiteleg shrimp (Penaeus vannamei) aquaculture, leading to high cumulative mortality and characteristic gross signs like whitened musculature. Conducted by ShrimpVet, the primary objectives of this study were to establish a validated, standardized experimental challenge method for IMNV infection in P. vannamei juveniles under controlled laboratory conditions, and to procure high-titer IMNV-infected shrimp for the consistent preparation of future inocula.
Healthy juvenile shrimp were acclimated and randomly allocated to experimental tanks in a recirculating system. The IMNV challenge inoculum was prepared from the abdominal muscle of infected shrimp, homogenized, and then serially diluted to create several distinct inoculum dose levels. These doses were administered to treatment groups via two methods: intramuscular (IM) injection and oral (per os) administration. The post-challenge period spanned 10-14 days.
Successful infection validation was confirmed using three criteria: (1) observation of characteristic gross signs; (2) histopathological confirmation of tissue pathology in moribund shrimp; and (3) quantitative detection of IMNV viral load in abdominal segments via PCR. The resulting optimized protocol and high-titer inoculum source provide a necessary and reproducible tool to advance clinical research against IMNV.
Keywords: Infectious Myonecrosis Virus, IMNV, Penaeus vannamei, Challenge Method, Dose Validation.