Viruses are ubiquitous and extremely abundant in the marine environment. One of such marine viruses, the white spot syndrome virus (WSSV), has emerged globally as one of the most prevalent, widespread and lethal for shrimp populations. However, at present there is no treatment available to interfere with the unrestrained occurrence and spread of the disease. The recent progress in molecular biology techniques has made it possible to obtain information on the factors, mechanisms and strategies used by this virus to infect and replicate in susceptible host cells. Yet, further research is still required to fully understand the basic nature of WSSV, its exact life cycle and mode of infection. This information will expand our knowledge and may contribute to developing effective prophylactic or therapeutic measures. This review provides a state-of-the-art overview of the topic, and emphasizes the current progress and future direction for the development of WSSV control strategies.

The White Spot Syndrome Virus (WSSV), the sole member of the family Whispoviridae, is the etiological agent that causes severe mortality events in wild and farmed shrimp globally. Given its adverse effects, the WSSV has been included in the list of notifiable diseases of the Office of International Epizootic (OIE) since 1997. To date there are no known therapeutic treatments available against this lethal virus, and a surveillance program in brood-stock and larvae, based on appropriate diagnostic tests, has been strongly recommended. However, some currently used procedures intended for diagnosis of WSSV may be particularly susceptible to generate spurious results harmfully impacting the shrimp farming industry. In this study, a sensitive one-step SYBR green-based real-time PCR (qPCR) for the detection and quantitation of WSSV was developed. The method was tested against several WSSV infected crustacean species and on samples that were previously diagnosed as being positive for WSSV from different geographical locations. A universal primer set for targeting the WSSV VP28 gene was designed. This method demonstrated its specificity and sensitivity for detection of WSSV, with detection limits of 12 copies per sample, comparable with the results obtained by other protocols. Furthermore, the primers designed in the present study were shown to exclusively amplify the targeted WSSV VP28 fragment, and successfully detected the virus in different samples regardless of their geographical origin. In addition, the presence of WSSV in several species of crustaceans, including both naturally and experimentally infected, were successfully detected by this method. The designed qPCR assay here is highly specific and displayed high sensitivity. Furthermore, this assay is universal as it allows the detection of WSSV from different geographic locations and in several crustacean species that may serve as potential vectors. Clearly, in many low-income import-dependent nations, where the growth of shrimp farming industries has been impressive, there is a demand for cost-effective diagnostic tools. This study may become an alternative molecular tool for a less expensive, rapid and efficient detection of WSSV.

Given its high prevalence, its wide distribution and its remarkable capacity to cause severe mortality in shrimp, the infectious hypodermal and haematopoietic necrosis virus (IHHNV) may deserve far more attention than it has received, as it remains considered as one of the most serious problems plaguing the global shrimp farming industry. Furthermore, its real measurable impact over wild shrimp populations remains unknown. Undeniably, the progress that we have reached today on the knowledge of its geographical distribution, clinical signs, genetic diversity, transmission and virulence may help to identify and understand important aspects of its biology and pathogenesis. However, the information regarding the molecular events that occur during the infection process is scarce. Thus, it may not be surprising to find that there are no therapeutic options available for the prophylaxis or treatments to reduce the deleterious impact of this viral pathogen to date. The aim of this review is to integrate and discuss the current state of knowledge concerning several aspects of the biology of IHHNV and to highlight potential future directions for this area of research.