Clinical signs, lethal dose and histopathological lesions in grass carp, Ctenopharyngodon idella experimentally infected with Edwardsiella tarda. (December 2021)

• Record Type: Journal Article
• Authors: Pandey, Vandana; Hussain Bhat, Raja Aadil; Chandra, Suresh; Tandel, Ritesh Shantilal; Dubey, Maneesh Kumar; Sharma, Prakash; Gehlot, Bhawna; Dash, Pragyan; Joshi, Rini
• Is Part Of: Microbial pathogenesis. Volume 161:Part B(2021)
• Publication Date: 2021-12
• Subjects: Edwardsiella tarda -- Grass carp -- Histopathology -- LD50; Pathogenic microorganisms -- Periodicals; Pathology, Molecular -- Periodicals; Communicable Diseases -- microbiology -- Periodicals; Communicable Diseases -- parasitology -- Periodicals; Micro-organismes pathogènes -- Périodiques; Pathologie moléculaire -- Périodiques; Electronic journals; 616.9041
• DOI: 10.1016/j.micpath.2021.105292
• Languages: English
• ISSNs: 0882-4010

Abstract

Abstract: An experiment was conducted to study the lethal dose (LD50 -96h) and histopathological changes occurring in several organs of grass carp challenged with different concentrations of Edwardsiella tarda . The healthy grass carps were challenged with the bacterial suspension of 10 6, 10 7, 10 8, 10 9 and 10 10 CFU ml −1 . The study demonstrated that the lethal dose (LD50 -96h) of E. tarda for grass carp is 1.3 × 10 9 CFU ml −1 . The infected fish showed abnormal swimming behavior, slower movements, skin necrosis, hemorrhages, and open lesion on the fontanelle of the frontal bone of the skull during the initial phase of infection. About 60% of the fish which received the bacterial suspension of 10 10 CFU ml −1 died within 24 h of infection. The histopathological examination of the infected tissue section demonstrated the severe damages in the internal organs. In gills, oedema, secondary lamellae fusion, and hyperplasia of basal epithelial lining between secondary lamellae were reported. The microscopic observation showed the disruption of submucosa to the mucosa, which finally led to degenerative changes in the intestine, necrosis of hepatocytes and infiltration of red blood cells in the liver. The tubular disintegration in kidney and loss of capsular boundary of red pulp in spleen were also reported. In conclusion, the result indicates that the infection caused by E. tarda can cause severe damages and alterations in grass carp tissues and potential mass mortality. Moreover, The bacteria isolated from the mobribund fish was characterized by biochemical tests and expression of five critical virulence genes like citC, fimA, gadB, mukF and gyrB were detected from the microorganism. The study aims to provide a research foundation for further studies on the susceptibility and pathological changes of grass carp induced by E. tarda infection. Highlights: LD50-96 h of E. tarda for grass carp is 1.3 × 10 9 CFU ml −1 60% of the fishes died within 24 h of infection after receiving the bacterial inoculum of 10 10 CFU ml −1 Expression of five critical virulence genes like citC, fimA, gadB, mukF and gyrB were detected by PCR. Pathological alterations were observed in internal organs.