The Global Diversity of Parasitic Isopods Associated with Crustacean Hosts (Isopoda: Bopyroidea and Cryptoniscoidea)

Parasitic isopods of Bopyroidea and Cryptoniscoidea (commonly referred to as epicarideans) are unique in using crustaceans as both intermediate and definitive hosts. In total, 795 epicarideans are known, representing ∼7.7% of described isopods. The rate of description of parasitic species has not matched that of free-living isopods and this disparity will likely continue due to the more cryptic nature of these parasites. Distribution patterns of epicarideans are influenced by a combination of their definitive (both benthic and pelagic species) and intermediate (pelagic copepod) host distributions, although host specificity is poorly known for most species. Among epicarideans, nearly all species in Bopyroidea are ectoparasitic on decapod hosts. Bopyrids are the most diverse taxon (605 species), with their highest diversity in the North West Pacific (139 species), East Asian Sea (120 species), and Central Indian Ocean (44 species). The diversity patterns of Cryptoniscoidea (99 species, endoparasites of a diverse assemblage of crustacean hosts) are distinct from bopyrids, with the greatest diversity of cryptoniscoids in the North East Atlantic (18 species) followed by the Antarctic, Mediterranean, and Arctic regions (13, 12, and 8 species, respectively). Dajidae (54 species, ectoparasites of shrimp, mysids, and euphausids) exhibits highest diversity in the Antarctic (7 species) with 14 species in the Arctic and North East Atlantic regions combined. Entoniscidae (37 species, endoparasites within anomuran, brachyuran and shrimp hosts) show highest diversity in the North West Pacific (10 species) and North East Atlantic (8 species). Most epicarideans are known from relatively shallow waters, although some bopyrids are known from depths below 4000 m. Lack of parasitic groups in certain geographic areas is likely a sampling artifact and we predict that the Central Indian Ocean and East Asian Sea (in particular, the Indo-Malay-Philippines Archipelago) hold a wealth of undescribed species, reflecting our knowledge of host diversity patterns

Potential of DIVA vaccines for Fish

The expanding aquaculture industry continues to encounter major challenges from highly contagious viruses. Control and eradication measures for lethal and economically damaging notifiable viral diseases involve ‘stamping out’ policies and surveillance strategies. Mass-culling of stock and restricted movement of fish and fish products, used to control the spread of notifiable diseases, has considerable impacts on the trade of fish products. Although effective, these measures are expensive and ethically complex and could possibly be reduced by emulating innovative vaccination strategies used by the terrestrial livestock industry. DIVA (differentiating infected from vaccinated animal) strategies provide a basis to vaccinate and contain disease outbreaks without compromising ‘disease-free’ status, as antibodies induced during infection can be used to distinguish from those induced by vaccination. The potential and feasibility of DIVA vaccination in aquaculture is explored here with reference to DIVA strategies applied in higher vertebrates. Three economically important notifiable viruses, causing major problems in three different cultured fish industries, are considered. The increased availability and application of sophisticated biotechnology tools has enabled improved prophylaxis and serological diagnosis for control of viral haemorrhagic septicaemia in rainbow trout, infectious salmon anaemia in Atlantic salmon and koi herpesvirus disease in carp. Improving the specificity of serological diagnostics in aquaculture in conjunction with suitable vaccines could enable the application of DIVA strategies, but the immunological variation between different fish species and contrasting pathobiological characteristics of different viruses determines the feasibility and potential of such DIVA approaches for aquaculture industries