A surveillance study on motile Aeromonas Septicemia (MAS) affecting cultured Litopenaeus vannamei shrimp from Suez Governorate, Egypt

This study aimed to investigate the prevalence of Aeromonas species among 150 cultured shrimp (Litopenaeus  vannamei) collected from commercial farms in the Suez Governorate, Egypt. Shrimp samples were subjected to bacteriological, molecular and histopathological examinations. Our results revealed that isolated bacteria were identified as Aeromonas hydrophila, based on morphological and phenotypic characteristics using traditional biochemical tests and commercial API20E kits. The results were genetically confirmed by conventional PCR assay using a specific set of primers targeting the Hemolysin gene. PCR yielded amplicons with a size of 130 bp which were the characteristics of A. hydrophila. The total prevalence of A. hydrophila among infected shrimp was 36.67%, whereas the lowest seasonal prevalence of infection was recorded in spring (26%), followed by summer (40%) and autumn (44%). The gross lesions of infected shrimp revealed black cuticular lesions, broken rostrum, rotten gills, and hepatopancreas discoloration. The histopathological examination of the infected hepatopancreas revealed cellular degeneration, sloughing of cells and necrosis, while the infected gills showed sloughing and atrophy of the branchial lamellae along with cell proliferation. The muscle also showed broken muscle fibers and haemocyte infiltrations. It was concluded that these bacterial strains badly infected the cultured shrimp. Thus, serious steps should be followed to avoid the outbreaks by using immunostimulants (herbal additives, prebiotics and probiotics) from the onset of the farming period.