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Infectious precocity virus (IPV) poses a significant economic threat to the aquaculture industry by causing sexual precocity and slow growth in Macrobrachium rosenbergii. In this study, we conducted an in-depth investigation into the genetic evolution of IPV from 2011 to 2024 by collecting 31 IPV variants through epidemiological surveys and public databases, including 29 variants with complete genomic sequences. The phylogenetic analysis revealed that these complete genomic sequences clustered into two distinct phylogenetic clades as follows: the Southeast Asian clade and the Chinese clade. Nucleotide and protein variation analyses demonstrated a high degree of similarity, with nucleotide identity ranging from 98.5% to 100% and protein identity from 99.4% to 100%. Further analysis of protein variations within the putative coding region identified two distinct variation patterns. The average dN/dS ratio of 0.12 highlights the strong purifying selection acting on IPV, particularly on structural proteins. In conclusion, this study significantly expands the genomic database of IPV and provides valuable insights into its genetic evolution. These findings offer critical scientific evidence to enhance detection protocols and support sustainable M. rosenbergii aquaculture practices.

The study delves into the largely uncharted territory of RNA viruses in crustaceans, which are not only vital for global food supply but also play a pivotal role in marine ecosystems. Focusing on economic crustaceans, the research uncovers 90 RNA viruses, with 69 being potentially new to science, highlighting the vast unknown viral diversity within these marine organisms. The findings reveal that these viruses are often related to those found in other invertebrates and tend to share close relationships with viruses from species within the same food web or habitat. This suggests that viruses may move between different marine species more frequently than previously thought. The discovery of such a wide variety of viruses, particularly the diverse genome structures of newly identified picornaviruses, is a significant leap forward in understanding the crustacean virology. This knowledge is crucial for managing disease risks in aquaculture and maintaining the balance of marine ecosystems.

Listeriosis is a zoonotic disease caused by Listeria monocytogenes (Lm), posing a significant threat to the breeding industry and public health. Ruminant livestock are particularly susceptible to Lm,  thus effective strategies are needed for controlling ovine listeriosis. In this study, we developed two inactivated vaccines and evaluated their efficacy against Lm infection in murine and ovine models. We inactivated the Lm serotype 4h XYSN strain and adjuvanted it with water-in-oil ISA 61 VG (61 VG-AIV) or aluminum (Al-AIV). Pathological observations confirmed the safety of both vaccines in mice and sheep. The immunological assays demonstrated that, compared with the Al-AIV, the 61 VG-AIV induced higher levels of Lm-specific antibodies and proinflammatory cytokines, suggesting that the ISA 61 VG adjuvant has superior immunostimulatory effects compared with the alum adjuvant. 61 VG-AIV elicited greater immunoprotection than Al-AIV (83.4% vs. 50%) against serotype 4h Lm strain challenge in mice. Additionally, 61 VG-AIV afforded cross-protection against challenges with serotypes 1/2a, 1/2b, and 4b Lm strains. Importantly, high immunoprotection in sheep was conferred by the 61 VG-AIV group (83.4%). Taken together, our findings demonstrate that the ISA 61 VG adjuvant contributes to enhancing the humoral and cellular immune responses of inactivated Lm, and 61 VG-AIV is a promising vaccine candidate for the prevention and control of animal listeriosis. This research lays a solid foundation for its application in veterinary medicine.

At present, there are few studies on the epidemiology of diseases in wild Chinese white shrimp Penaeus chinensis. In order to enrich the epidemiological information of the World Organisation for Animal Health (WOAH)-listed and emerging diseases in wild P. chinensis, we collected a total of 37 wild P. chinensis from the Yellow Sea in the past three years and carried out molecular detection tests for eleven shrimp pathogens. The results showed that infectious hypodermal and hematopoietic necrosis virus (IHHNV), Decapod iridescent virus 1 (DIV1), yellow head virus genotype 8 (YHV-8), and oriental wenrivirus 1 (OWV1) could be detected in collected wild P. chinensis. Among them, the coexistence of IHHNV and DIV1 was confirmed using qPCR, PCR, and sequence analysis with pooled samples. The infection with YHV-8 and OWV1 in shrimp was studied using molecular diagnosis, phylogenetic analysis, and transmission electron microscopy. It is worth highlighting that this study revealed the high prevalence of coinfection with YHV-8 and OWV1 in wild P. chinensis populations and the transmission risk of these viruses between the wild and farmed P. chinensis populations. This study enriches the epidemiological information of WOAH-listed and emerging diseases in wild P. chinensis in the Yellow Sea and raises concerns about biosecurity issues related to wild shrimp resources.

Lined seahorse, Hippocampus erectus, is an important aquatic animal due to its medicinal and ornamental purposes. However, our understanding of the viral spectrum in H. erectus is still limited. Here, we studied the viruses in H. erectus using meta-transcriptomic sequencing. A total of 213,770,166 reads were generated and assembled de novo into 539 virus-associated contigs. Three novel RNA viruses from the Astroviridae, Paramyxoviridae, and Picornaviridae families were finally identified. In addition, we identified a strain of nervous necrosis virus from H. erectus. In particular, the unhealthy group showed a higher viral diversity and abundance than the normal group. These results revealed the diversity and cross-species transmission of viruses in H. erectus and highlighted the threat of viral infections to H. erectus.

Perinereis species are essential benthonic animals in coastal ecosystems and have significant roles as live feed in aquaculture, owing to their high-protein and low-fat nutritional profile. Despite their ecological importance, the viral communities associated with these organisms need to be better understood. In this study, we generated 2.6 × 108 reads using meta-transcriptomic sequencing and de novo assembled 5.3 × 103 virus-associated contigs. We identified 12 novel RNA viruses from two species, Perinereis aibuhitensis and P. wilsoni, which were classified into four major viral groups: Picobirnaviridae, Marnaviridae, unclassified Picornavirales, and unclassified Bunyavirales. Our findings revealed the hidden diversity of viruses and genome structures in Perinereis, enriching the RNA virosphere and expanding the host range of Picobirnaviridae, Marnaviridae, and Bunyavirales. This study also highlighted the potential biosecurity risk of the novel viruses carried by Perinereis to aquaculture.

The iron prawn syndrome (IPS), also described as sexual precocity, results in the reduced size of farmed prawns at harvest and significant economic losses. IPS has been frequently reported in populations of farmed Macrobrachium rosenbergii since 2010, but the cause was heretofore unknown. Since 2010, sexual precocity, a typical sign of the iron prawn syndrome (IPS), resulting in the reduced size of farmed giant freshwater prawns Macrobrachium rosenbergii , has caused substantial production losses. However, the cause of IPS was not clear. We ran tests for eight major shrimp pathogens, but none were detected from IPS-affected prawns. We performed the histopathological examination of tissues and identified an eosinophilic inclusion in the perinuclear cytoplasm of cells in various tissues associated with nervous and endocrinal functions in the compound eyes. A subsequent bioassay with viral extracts of IPS-affected samples reproduced the gross signs of IPS. Metatranscriptomic sequencing identified a novel virus of Flaviviridae in all IPS-affected M. rosenbergii prawns, which was not found in samples without IPS. This virus contains a positive-sense, single-stranded RNA genome of 12,630 nucleotides (nt). Phylogenetic analysis of the conserved RdRp and NS3 domains showed that it may belong to a new genus between Jingmenvirus and Flavivirus . Under transmission electron microscopy (TEM), putative virus particles showed as spherical with a diameter of 40 to 60 nm. In situ hybridization found hybridization signals consistent with the histopathology in the compound eyes from IPS-affected M. rosenbergii . We provisionally name this virus infectious precocity virus (IPV) and propose the binominal Latin name Crustaflavivirus infeprecoquis gen. nov., sp. nov. We developed a nested reverse transcription-PCR diagnostic assay and confirmed that all IPS-affected prawns tested IPV positive but normal prawns tested negative. Collectively, our study revealed a novel virus of Flaviviridae associated with sexual precocity in M. rosenbergii . IMPORTANCE The iron prawn syndrome (IPS), also described as sexual precocity, results in the reduced size of farmed prawns at harvest and significant economic losses. IPS has been frequently reported in populations of farmed Macrobrachium rosenbergii since 2010, but the cause was heretofore unknown. Here, we reported a novel virus identified from prawns with IPS using infection experiments, metatranscriptomic sequencing, and transmission electron microscopy and provisionally named it infectious precocity virus (IPV). Phylogenetic analysis showed that IPV represents a new genus, proposed as Crustaflavivirus gen. nov., in the family Flaviviridae . This study provides novel insight that a viral infection may cause pathological change and sexual maturation and subsequently affect crustacean growth. Therefore, we call for quarantine inspection of IPV in transboundary trade of live M. rosenbergii and enhanced surveillance of IPV in aquaculture in the region and globally.

The study utilised a pasture grazing based, voluntary traffic automatic milking system to investigate milk production of cows fed a pasture-based diet and supplemented with a pellet formulated with vs. without rumen-protected lysine and methionine (RPLM). The study adopted a switch-over design (over two periods of 5 and 10 weeks, respectively) and used 36 cows and equally allocated them into two experimental groups. The RPLM (Trial) pellet had 2% lower crude protein, but similar metabolizable energy content compared to the Control pellet. Pellet intake was 10.0 and 9.4 kg/day/cow. Milk yield was 36.2 and 34.4 kg/day/cow (p = 0.23), and energy corrected milk was 35.1 and 33.8 kg/day/cow (p = 0.076), and milk solids was 2.55 and 2.46 kg/cow/day (p = 0.073) in the Control and Trial groups, respectively. Milk fat%, milk protein%, milk fat: protein ratio, milking frequency and rumination time were not different between the two groups (p > 0.05). In period 1, plasma glucose was 3.1 mmol/L for both groups and milk urea were 150 and 127 mg/L in the Control and Trial groups, respectively. Both plasma glucose (as a proxy for energy supply) and milk urea (as a proxy for nitrogen use efficiency; NUE) were not different between groups (p > 0.05). This study showed that under a grazing pasture system, feeding lactating dairy cows a low protein pellet with RPLM supplementation, maintained milk production performance and NUE, compared with cows fed a high protein Control pellet diet with no RPLM. Further research should assess the long-term (seasonal) effects of feeding a diet formulated with RPLM on cow intake, health and reproductive performance.

In a meta-transcriptome study of the giant freshwater prawn Macrobrachium rosenbergii sampled in 2018 from a hatchery, we identified a variant of Macrobrachium rosenbergii golda virus (MrGV) in postlarvae without clinical signs. The virus belongs to the family Roniviridae, and the genome of this MrGV variant, Mr-18, consisted of 28,957 nucleotides, including 4 open reading frames (ORFs): (1) ORF1a, encoding a 3C-like protein (3CLP) (4933 aa); (2) ORF1b, encoding a replicase polyprotein (2877 aa); (3) ORF2, encoding a hypothetical nucleocapsid protein (125 aa); and (4) ORF3, encoding a glycoprotein (1503 aa). ORF1a overlaps with ORF1b with 40 nucleotides, where a −1 ribosomal frameshift with slippage sequence 5′-G14925GGUUUU14931-3′ produces the pp1ab polyprotein. The genomic sequence of Mr-18 shared 97.80% identity with MrGV LH1-2018 discovered in Bangladesh. The amino acid sequence identities between them were 99.30% (ORF1a), 99.60% (ORF1b), 100.00% (ORF2), and 99.80% (ORF3), respectively. Phylogenetic analysis of the RNA-dependent RNA polymerase (RdRp) proteins revealed that they clustered together and formed a separate cluster from the genus Okavirus. The finding of MrGV in China warrants further studies to determine its pathogenicity and prevalence within the region.

Listeria monocytogenes (Lm) is a ubiquitous foodborne pathogen comprising of 14 serotypes, of which serovar 4h isolates belonging to hybrid sub-lineage Ⅱ exhibit hypervirulent features. LMxysn_1693 of serovar 4h Lm XYSN, a member of genomic island-7 (GI-7), is predicted to a membrane protein with unknown function, which is conserved in serovar 4h Listeria monocytogenes. Under bile salts stress, Lm XYSN strain lacking LMxysn_1693 (XYSN∆1693) exhibited a stationary phase growth defect as well as a reduction in biofilm formation and strikingly down-regulated bile-salts-resistant genes and virulent genes. Particularly, LMxysn_1693 protein plays a crucial role in Lm XYSN adhesion and invasion to intestinal epithelial cells, as well as colonization in the ileum of mice. Taken together, these findings indicate that the LMxysn_1693 gene encodes a component of the putative ABC transporter system, synthetically interacts with genes involved in bile resistance, biofilm formation and virulence, and thus contributes to Listeria monocytogenes survival within and outside the host.