Artemia franciscana as a vector for infectious myonecrosis virus (IMNV) to Litopenaeus vannamei juvenile.

In 2004, the infectious myonecrosis virus (IMNV) was recognized as the main cause of Litopenaeusvannamei shrimp culture's drop in Brazil. In health animal control programs, in order to reduce virus prevalence in production units it is necessary to screen live feed used. Among live diets used in aquaculture, the brine shrimp Artemia sp. is essential in crustacean larviculture and maturation. The aim of the present study was to investigate the susceptibility of Artemiafranciscana to IMNV through an immersion challenge and virus-phytoplankton adhesion route and to elucidate its role as a vector for IMNV transmission to L.vannamei. A. franciscana adults were infected with IMNV through both routes, as demonstrated by PCR-positive reactions. However, infected A. franciscana showed no signs of infection. More than 40% of L. vannamei juveniles fed with IMNV-infected A. franciscana by virus-phytoplankton adhesion route were positive by real-time PCR, whereas only a 10% infection rate was found among shrimp fed with IMNV-infected brine shrimp using the immersion challenge. Significant differences were found in mean viral load between immersion and virus-phytoplankton adhesion shrimp treatments (p ⩽ 0.05). Moreover, the mean viral loads were 1.34 × 10(2) and 1.48 × 10(4) copies/μg(-1) of total RNA for virus-phytoplankton adhesion and IMNV-infected tissue treatments, respectively, and the difference was not significant (p ⩾ 0.05). The results indicated that A. franciscana act as a vector for IMNV transmission under the experimental conditions examined. Although no mass mortalities were detected in L. vannamei fed with IMNV-infected brine shrimp, these infected shrimp should not be disregarded as a source of IMNV in grow-out units.