Assessment of Gill Pathological Responses in Yellowfin Sea Bream (Acanthopagrus Latus) Under Aeromonas Hydrophila Exposure.

Bacterial diseases in cultured fish are considered the main problem with aquaculture system in Iran. The gills are multifunctional organs responsible for respiration, osmoregulation, nitrogenous waste excretion, and acid-base balance. Moreover, they are very sensitive to water contamination. Aeromonas hydrophila (A. hydrophila) is an opportunist pathogen responsible for a wide range of diseases in different species of fish. The gill histological alterations were used to assess the effects of A. hydrophila exposure on yellowfin sea bream, Acanthopagrus latus (A. latus). In this regard, 90 A. latus were exposed to the concentrations of A. hydrophila (103 and 106 CFU/ml) for three weeks. The most histopathological alterations in the gill of the exposed fish included hypertrophy and hyperplasia of the epithelial cells, lamellar fusion, club shaping of gill lamellae, lifting of the epithelium and edema of lamellae with large sub-epithelial space, blood congestion, and hypertrophy and hyperplasia of the mucosal cells. The histopathological alterations were observed in the gill of fish exposed to higher levels of A. hydrophila (106 CFU/ml) consisted of aneurysm and hemorrhage with blood congestion. According to the obtained results of this study, A. hydrophila could cause severe histopathological changes in the gill of A. latus and decrease gas change capability in yellowfin sea bream. Furthermore, the findings of the present study suggested that histopathological changes of the gill provide helpful information about the environmental conditions and as particular biomarkers may help the evaluation of fish general health.

Ulcer disease prophylaxis in koi carp by bath immersion with chicken egg yolk containing anti-Aeromonas salmonicida IgY.

Ulcer disease, caused by atypical Aeromonas salmonicida, is a serious concern in ornamental koi carp, because it induces skin ulceration, disfiguring ornamental fish and causing economic loses. The present study aimed to establish a novel prophylaxis with chicken egg yolk immunoglobulin, IgY, against ulcer disease and to assess its feasibility in the ornamental fish industry. Addition of egg yolk powder containing anti-A. salmonicida IgY to rearing water provided significant protection against an A. salmonicida bath infection, whereas administration of non-specific IgY did not. Consecutive immersion of fish into rearing water containing specific IgY completely prevented ulcer disease resulting from cohabitation infection, indicating that this prophylaxis could prevent infection from such type of contact. Thus, passive immunization induced by immersing fish into aquarium water containing specific IgY is a prospective prophylaxis against diseases caused by pathogens that invade the skin and gills.

Field assessment of the mid winter mass kills of trophic fishes at Mariotteya stream, Egypt: chemical and biological pollution synergistic model.

Pathogenic Candida albicans was isolated from water and fish samples collected during an emergent event of mass mortalities among the juvenile Nile tilapia (Oreochromis niloticus), Sharp toothed catfish (Clarias gariepinus) along the stream of Mariotteya drainage. Investigations indicated that fish mortalities were confined to the area of Shubramant and Aboul Noumros (North to Sakara 7 drainage). C. albicans was isolated from the lesions associated with multiple skin ulcers in both Nile tilapia juveniles and Sharp toothed catfish. Assessment of the field and laboratory data has indicated that Mariotteya environmental disaster was a multifactorial problem. The fish mass kills were initially flared up through the dumping of the improperly treated nasty organic and inorganic chemicals from Elhawamdia sugar factory and municipal sewage. The physical stagnation of the stream, high levels of ammonia, phenol and polycyclic aromatic hydrocarbons (PAHs) and low levels of dissolved oxygen (DO) were all incriminated as the initial stimulus behind biological invasion of pathogenic bacteria (Pseudomonas fluorescence) and yeast (C. albicans). Pathologically, fishes were dying from both respiratory and osmoregulatory failure induced by the severe damage of both gills and skin. It has been implied that such environmental pollutants have direct damaging effects on gills, skin and fins with consequent suppression of the skin's natural innate components. The adversely confronted immunological barriers were further exacerbated by the possible synergistic interactions of P. fluorescence dermotropic toxins followed by the secondary invasion of the pathogenic C. albicans.

Comparison of rRNA and polar-lipid-derived fatty acid biomarkers for assessment of 13C-substrate incorporation by microorganisms in marine sediments.

We determined whether a recently developed method to isolate specific small-subunit (SSU) rRNAs can be used in 13C-labeling studies to directly link community structure and function in natural ecosystems. Replicate North Sea sediment cores were incubated at the in situ temperature following addition of 13C-labeled acetate, propionate, amino acids, or glucose. Eukaryotic and bacterial SSU rRNAs were separated from total RNA by means of biotin-labeled oligonucleotide probes and streptavidin-coated paramagnetic beads, and the 13C content of the isolated rRNA was determined by elemental analysis-isotope ratio mass spectrometry. The SSU rRNA yield with the bead-capture protocol was improved by using helper probes. Incorporation of label into bacterial SSU rRNA was detectable after 2 h of incubation. The labeling was always much greater in bacterial SSU rRNA than in eukaryotic SSU rRNA, suggesting that bacteria were the main consumers of the 13C-labeled compounds. Similar results were obtained with the 13C-labeled polar-lipid-derived fatty acid (PLFA) approach, except that more label was detected in bacterial PLFA than in bacterial SSU rRNA. This may be attributable to the generally slow growth of sediment microbial populations, which results in low ribosome synthesis rates and relatively few ribosomes per cell. We discuss possible ways to improve the probe-capture protocol and the sensitivity of the 13C analysis of the captured SSU rRNA.

Increased efficacy of immersion vaccination in fish with hyperosmotic pretreatment.

Immersion vaccination is common practice in aquaculture, because of its convenience for mass vaccination with sufficient protection. However, the mechanisms of antigen uptake and presentation, resulting in a protective immune response and the role of the innate immune system therein are largely unknown. The impact of immersion vaccination on fish physiology and on the ensuing innate and specific immune response was characterized with fluorescently labeled particulate and soluble model antigens. Vaccination of common carp by direct immersion (DI) or hyperosmotic immersion (HI; direct immersion, preceded by a brief immersion in a hypertonic solution) greatly enhanced the uptake of soluble, but not particulate antigen through temporary disruption of the integrity of the epithelia of gills and skin. Damage induced is mild and does not impose additional stress over the handling associated with immersion vaccination. Especially HI briefly but strongly activates the innate immune system. We conclude that HI more effectively increased the uptake of vaccine and enhanced the efficacy by which vaccine components are processed and presented by the innate immune system, dually enhancing the mucosal immune response. Understanding the mechanisms involved in uptake and processing of vaccine in the early phase of the immune response will greatly benefit the design of immersion vaccination.