First identification and histopathological analysis of Lactococcus garvieae infection in whiteleg shrimp, Penaeus vannamei cultured in low salinity water

Abstract

The isolation and characterization of bacterial species Lactococcus garvieae, previously unreported in whiteleg shrimp, Penaeus vannamei, has now been identified in the species. The pathogen was recovered from an affected shrimp farm in southern Taiwan. Bacterial characterization first identified the isolate as Gram‐positive cocci, and biochemical profiles demonstrated that the causative agent of mortality was 97% L. garvieae. The bacterial cell DNA resulted in amplification of 1522 bp with 99.6% confirmation by PCR analysis. The phylogenetic tree revealed 100% evolutionary similarity among previously isolated strains. Experimental infection further confirmed higher susceptibility of whiteleg shrimp to L. garvieae in waters of lower salinity, particularly 5 ppt, than in higher salinity. Histopathological analysis showed severely damaged hepatopancreas with necrotized, elongated, collapsed tubules, dislodged membranes and granuloma formation in infected shrimp. Transmission electron microscopy observation indicated a hyaluronic acid capsular layer surrounding bacterial cell which is a virulence factor of L. garvieae and likely responsible for immunosuppression and higher mortality of shrimp cultured in lower salinity. Collectively, these findings report the first isolation of L. garvieae from whiteleg shrimp and shed new light on the disease that threatens the highly valuable species and accentuates the need for finding a solution.

Effects of polystyrene nanoplastics on apoptosis, digestive enzymes, and intestinal histological structure and flora of swamp eel (Monopterus albus)

“…In aquaculture, L. garvieae is an important pathogen that has been reported to cause severe infections in aquatic organisms, such as fish and shrimp. 48,49 L. garvieae also causes septicemia and endocarditis in humans. 50 It can also effectively evade host immune system monitoring and attack by producing polysaccharide pods, 51,52 which can impact immune recognition of the surface of the bacteria, making it difficult for immune cells to recognize and attack them.…”

First identification, molecular characterization, and pathogenicity assessment ofLactococcus garvieaeisolated from cultured pompano in Taiwan

“…Thus, understanding the genetics and regulation of capsular gene clusters in L. garvieae is crucial for developing effective disease prevention and treatment strategies (Shi et al, 2019). Interestingly, recent studies have suggested the possibility of multiple types of capsules in L. garvieae, such as the hyaluronic acid capsule, observed in L. garvieae isolated in whiteleg shrimp (Penaeus vannamei) and in cobia (Ballantyne et al, 2023;Rao et al, 2021). So, a thick capsule like structure observed in our In this study, PFGE and phylogenetic analyses were conducted to determine the genotypes of the isolates.…”

Effects of Feed Processing Type, Protein Source, and Environmental Salinity onLitopenaeus vannameiFeeding Behaviour

“…As climate change affects salinity patterns globally, understanding its impact on shrimp is essential for developing adaptive feeding strategies. Studies have shown that water salinity and dietary protein content significantly affect the growth performance of L. vannamei juveniles, with better performance observed at higher salinity and protein levels (Bardera et al, 2019; Rahi et al 2021; Pinho and Emerenciano, 2021; Ballantyne et al, 2023;). While the long-term impacts of salinity on shrimp have been explored, the immediate effects on feeding behaviour and how it interacts with environmental conditions remain under-studied.…”