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Pacific oysters (Crassostrea or Magallana gigas) are one of the most economically important aquaculture species globally. Over the past two decades, ostreid herpesvirus (OsHV-1) has become a major pathogen of cultured Pacific oysters, resulting in widespread mortality with a global distribution. Experimental use of OsHV-1 is challenging for many reasons, including both complexity of host–pathogen dynamics and a lack of functioning model systems. The goal of this study was to improve the tools available for working with OsHV-1 in both whole animals and in tissue explants established from oysters maintained in controlled laboratory conditions. Tissue explants were taken from oysters originating from two different sources that have different levels of mortality in experimental OsHV-1 infections and were exposed to OsHV-1. A whole-animal infection experiment was run concurrently as a comparison. Quantitative PCR and electron microscopy were used to confirm that the explants were capable of replicating OsHV-1. Furthermore, the quantitative PCR results suggest that the source of the oysters was significant in determining the outcome of infection in the explants, supporting the validity of the explant model for OsHV-1 infection. This tissue explant approach for studying OsHV-1 allows for the control of confounding factors in the disease outcome that is not possible in whole-animal experiments, providing a new tool for the study of OsHV-1 in Pacific oysters. [ABSTRACT FROM AUTHOR]

The giant river prawn, Macrobrachium rosenbergii, is a major focus of aquaculture in tropical and sub‐tropical regions around the globe. Over the last 30 years, culture of M. rosenbergii has increased exponentially as demand has risen both for domestic consumption and for international export trade. As with many aquaculture species increases in production have been accompanied by the emergence of diseases affecting yield, profit and trading potential. Disease‐causing agents include pathogens infecting other crustaceans, such as Decapod Iridescent Virus (DIV1), as well as pathogens only known from M. rosenbergii such as White Tail Disease caused by Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus (XSV). Here, we review the pathogenic agents associated with the culture of M. rosenbergii since commercial culture began in earnest during the 1970s. Particular emphasis is given to pathogens first identified in other aquaculture host species, but which have subsequently been shown to infect and cause disease in M. rosenbergii. As polyculture of M. rosenbergii with other aquaculture species is common practice, including culture with other decapods, crabs and fish, increased pathogen transfer among these farmed species may occur as M. rosenbergii aquaculture increases in the future. [ABSTRACT FROM AUTHOR]

This study provides a morphological and phylogenetic characterization of two novel species of the order Haplosporida (Haplosporidium carcini n. sp., and H. cranc n. sp.) infecting the common shore crab Carcinus maenas collected at one location in Swansea Bay, South Wales, UK. Both parasites were observed in the haemolymph, gills and hepatopancreas. The prevalence of clinical infections (i.e. parasites seen directly in fresh haemolymph preparations) was low, at ~1%, whereas subclinical levels, detected by polymerase chain reaction, were slightly higher at ~2%. Although no spores were found in any of the infected crabs examined histologically (n = 334), the morphology of monokaryotic and dikaryotic unicellular stages of the parasites enabled differentiation between the two new species. Phylogenetic analyses of the new species based on the small subunit (SSU) rDNA gene placed H. cranc in a clade of otherwise uncharacterized environmental sequences from marine samples, and H. carcini in a clade with other crustacean-associated lineages. [ABSTRACT FROM AUTHOR]

White spot disease in penaeid shrimp is caused by the white spot syndrome virus (WSSV). It is the most economically important disease of farmed warm‐water shrimp, causing extensive economic losses estimated from $8 to $15 billion since its emergence in the 1990s. Early diagnosis of disease is critical in the management of outbreaks and to avoid crop losses. Diagnosis of white spot disease is generally carried out in centralized laboratory settings using molecular biology approaches. However, this mode of testing can be expensive and time consuming, requiring laboratory equipment, highly trained laboratory personnel, dedicated laboratory space, and long‐distance transportation of samples from field to lab. In‐field diagnostics are gaining credence as tools for rapid and early animal disease detection, allowing diagnosticians and farmers to potentially manage disease outbreaks from the pond side. In the present study, we describe the development and application of a new in‐field point‐of‐need diagnostic test and platform for the diagnosis of WSSV in remote settings (shrimp farms). We report its performance in laboratory and field settings and compare it with current gold‐standard diagnostic approaches. We discuss the potential benefits (and barriers to uptake) of applying such testing in the global shrimp farming sector. [ABSTRACT FROM AUTHOR]