Hypoxia increases susceptibility of Pacific white shrimp to whitespot syndrome virus (WSSV)

M Lehmann,D.D Schleder,L.M Perazzolo,C Guertler,L Vinatea

doi:10.1590/1678-4162-7942

Abstract

The present study aimed to evaluate the mortality, reactive oxygen species production (ROS) and total hemocyte counts (THC) of the marine shrimp Litopenaeus vannamei infected with the white spot syndrome virus (WSSV) at three levels of oxygen saturation. For this, 360 shrimp (20±2g) were distributed in 24 tanks (60L), divided in two groups (infected and non-infected), which were subjected to 30, 60 and 100% of dissolved oxygen saturation (in quadruplicate). During 96 hours after infection, daily hemolymph samples were collected for hemato-immunological parameter evaluation (THC and ROS) and dead animals were removed and computed to assess cumulative mortality rates. In the infected group, animals subjected to 100% saturation showed higher ROS production (P<0.05) after 48 hours, while THC was significantly reduced (P<0.05), regardless of oxygen saturation. The hypoxia resulted in high mortality when compared to 100% saturation condition. In the uninfected group, no significant differences were observed in all evaluated parameters. Thus, the hypoxia condition increased the susceptibility of shrimp to the infection of WSSV, which may be partly related to the low ROS production showed by the animals subjected to 30% oxygen saturation.

Highlights

Diseases are the result of an unbalanced interaction between pathogen, environment and host
There is no immunological memory in these animals, and the non-self recognition depends on pattern recognition proteins (PRPs) that detect pathogen-associated molecular patterns (PAMPs)
No mortality and no abnormal behaviors were observed in the animals from the uninfected treatments

Summary

Introduction

Diseases are the result of an unbalanced interaction between pathogen, environment and host. An animal in a safe environment may carry an infectious agent without manifesting signs of the disease. In the production of aquatic organisms, the occurrence of inadequate water quality parameters may disturb their homeostasis, leading to increased susceptibility to diseases (Le Moullac and Haffner, 2000). Like other invertebrates, protection against diseases solely depends on the innate immune system. There is no immunological memory in these animals, and the non-self recognition depends on pattern recognition proteins (PRPs) that detect pathogen-associated molecular patterns (PAMPs). The innate immune system of invertebrates is related to their hemolymph, composed of a cellular fraction (hemocytes) and a liquid fraction (plasma), where humoral factors are dissolved (Barracco et al, 2008)

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Conclusion