Abstract
Hematodinium is a parasitic dinoflagellate and emerging pathogen of crustaceans. It preferably manifests in haemolymph of marine decapod crustaceans, killing a large variety of genera with significant impacts on fisheries worldwide. There is, however, evidence that some crustacean stocks harbor high prevalence, low intensity infections that may not result in widespread host mortality and are therefore hard to detect. The most widely used methods for detection of Hematodinium are conventional blood smears and polymerase chain reaction (PCR) against ribosomal RNAs. Blood smears demand a trained investigator, are labor intensive and not readily scalable for high-throughput sampling. PCRs only detect parasite DNA and can also suffer from false negatives and positives. In order to develop alternative detection tools for Hematodinium cells in decapod crustaceans we employed an immunological approach against a newly identified, abundant dinoflagellate-specific nuclear protein—Dinoflagellate/Viral NucleoProtein (DVNP). Both immunofluorescence assay (IFA) and Western blot methods against DVNP showed high sensitivity of detection. The Western blot detects Hematodinium parasites to levels of 25 parasites per milliliter of crustacean haemolymph, with the potential for sample pooling and screening of large samples. Using both PCR and these new tools, we have identified Hematodinium cells present in three new host crab taxa, at high prevalence but with no sign of pathogenesis. This extends the known range of Hematodinium to southern Australia.
Highlights
Hematodinium is a genus of parasitic dinoflagellates that infect the haemolymph of marine decapod crustaceans [1]
We have explored the use of Dinoflagellate/Viral NucleoProtein (DVNP) antibodies for detection of Hematodinium cells by both immunofluorescence assay (IFA) and Western blots, and identify this as a potent new strategy in detecting and/or corroborating presence of this parasite in decapod host samples
We investigated whether Hematodinium could be detected by anti-DVNP IFA in freshly fixed haemolymph of polymerase chain reaction (PCR)-positive L. gaimardii from Port Phillip Bay that were maintained in captivity
Summary
Hematodinium is a genus of parasitic dinoflagellates that infect the haemolymph of marine decapod crustaceans [1]. During the past four decades, epizootics of Hematodinium were described from many decapod crustacean stocks in the USA, the UK, Europe and Australia and often cause significant economical loss to associated fisheries [1,7,8]. Extensive field surveys in some decapod stocks suggest that clear seasonal peaks with high intensity infections and disease are interspersed with periods of low infection intensity [14] during which prevalence remains high [15]. This suggests slow progression to disease in large numbers of the population. The seasonal nature of disease outbreaks and the influence of environmental factors raises the possibility that the host-range of Hematodinium may be greater than might be suggested by monitoring only for the incidence of disease
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