Pasteurellosis in Atlantic salmon, Salmo salar L.: immunohistochemistry of the naturally-occurring disease

Protective effect of apple mangrove Sonneratia caseolaris extract in Edwardsiella tarda-infected African catfish, Clarias gariepinus

Outbreaks of edwardsiellosis have severe impact on the aquaculture production of African catfish Clarias gariepinus. In this study, feed supplemented with apple mangrove Sonneratia caseolaris extract was evaluated for its protective effect against Edwardsiella tarda infection in African catfish. Results showed an increase in growth performance and higher survival rate in the treatment groups in a dose dependent manner. Haematological analyses showed an increase in white blood cell count in the treatment groups. Histopathological analysis revealed degenerative changes and regeneration of liver tissue architecture in both the control and treatment groups. However, the presence of inflammatory cells was found exclusively in the kidney of T3 treatment group that was supplemented with the highest dose of extract at 3.17 mg/ml, which inferred the activation of immune response in the fish. Contrast to the deteriorative alteration observed in the kidney of the control group due to E. tarda infection, treatment group exhibited tissue regeneration and well-defined kidney tissue architecture at 3 dpi. Taken together, these results demonstrated that supplementation with the methanol extract of S. caseolaris possesses protective effect in African catfish against the infection of E. tarda.

Molecular and phenotypic characterization of Photobacterium damselae among some marine fishes in Lake Temsah

Photobacterium damselae species are one of the most devastating bacterial pathogens in mariculture worldwide. Some species of Photobacterium are pathogenic for marine animals and human. They are the causative agents of photobacteriosis, formerly known as pasteurellosis. A total of (202) marine fishes of three different species were represented as: seabass (Dicentrarchus labrax), seabream (Sparus aurata) and gray mullet (Mugil capitus) randomly collected from Lake Temsah at Ismailia governorate along the parallel Pelagic road to the lake in the governorate from August 2015 to July 2016. The clinical picture and gross lesions of the diseased fishes were recorded. Isolation and identification of suspected bacteria using traditional and molecular methods. Samples from affected organs were collected for studying the histopathological alterations of these pathogens. Fifty one fishes were found to be infected with Photobacterium damselae subsp. Piscicida. Seabass (Dicentrarchus labrax) was the most infected fish species (23), followed by seabream (Sparus aurata) (18) finally gray mullet (Mugil capitus) was (10). 91fishes were found to be infected with P. damselae subsp. damselae, seabass (Dicentrarchus labrax) was the most infected fish sp. (36), followed by seabream (Sparus aurata) (32), then gray mullet (Mugil capitus) (23). The results indicated that, the total prevalence of P. damselae subsp. piscicida in all examined species (25.24%), the highest seasonal prevalence was recorded in summer season (37.09%) followed by autumn (26%) then spring (20.37%) and winter (11.11%). On the other hand, the total prevalence of P. damselae subsp. damselae in all examined species (45.04%), the highest seasonal prevalence was recorded in summer season (67.74%) followed by autumn (52%) then spring (29.62%) and winter (19.44%). Molecular diagnosis with conventional PCR used to confirm the traditional isolation was applied by using specific primers of two genes (polycapsular saccharide gene and urease C gene). The histopathological studies of naturally infected marine fishes showed severe inflammatory reactions in different organs with accumulation of melanomacrophages and necrosis. The results confirm that P. damselae subspecies damsalea is the most prevalent pathogen between marine fishes, and seabass (Dicentrarchus labrax) was the highly affected marine fishes in this study.