Evaluating the effect of temperature on Penaeus vannamei culture in a heterotrophic system and experimentally infected with the infectious myonecrosis virus

Abstract

Causing economic losses in Brazil and Indonesia between 2002 and 2011 of over US$ 1 billion, infectious myonecrosis (IMN) constitutes a disease of mandatory notification to WHO (World Health Organization) and is responsible for constant damages in the production of the marine shrimp Penaeus vannamei. Although environmental factors such as high thermal amplitude, high concentration of nitrogen compounds and abrupt changes in salinity can alter the infection rate of this disease, there are still no studies. Thus, the present work aimed to evaluate the influence of temperature on the infectivity of IMNV in P. vannamei culture in a heterotrophic system. The experiment lasted 42 days, divided into two stages: (i) subjecting the shrimps to different temperatures (26 °C, 29 °C, 32 °C, and 35 °C) for 21 days; and (ii) viral challenge with IMNV via intramuscular injection (100 μL) also for 21 days, with evaluation of the shrimps by nested-PCR, histopathology and total and differential hemocyte count. The results obtained indicated that shrimps submitted to the highest temperatures evaluated (32 °C and 35 °C) had the highest post-viral challenge survival rates (85.42% and 93.75%, respectively), with less presence of lesions suggestive of IMN, although these shrimps were still positive by nested-PCR. No significant differences were observed in total hemocyte counts between pre- and post-challenge treatments (P > 0.05). In conclusion, the use of a temperature of 35 °C reduced mortality and viral load but altered the feed absorption, generating a reduction in zootechnical performance.