Dietary Application of the Probiotic Lactobacillus plantarum 426951 Enhances Immune Status and Growth of Rainbow Trout (Oncorhynchus mykiss) Vaccinated Against Yersinia ruckeri.

This study was aimed to assess the effect of oral application of Lactobacillus plantarum (2 × 107 CFU g-1 feed) as a probiotic on growth performance and immune status of vaccinated rainbow trout (29.5 ± 2 g) to yersiniosis at 16 ± 2 °C for 72 days. Fish were randomly allocated into 12 fiber glass tanks (4100 L) at a density of 80 fish per tank (240 fish per treatment). The results revealed that the activity of lysozyme and alkaline phosphatase was significantly higher in immunized fish fed with diet supplemented with probiotic (vaccine +probiotic) than that in the immunized group fed with basal diet (vaccine group) while no significant differences in levels of hematological parameters, complements, total IgM, proteins, and the intestine lactic acid bacteria (LAB) were detected. Also, significantly a better growth performance in terms of feed conversion ratio, weight gain, and thermal growth coefficient was seen in the vaccine + probiotic group than that in the vaccine group. These results indicate that feeding probiotic after vaccination can enhance the efficacy of immersion vaccination to Yersinia ruckeri.

Occurrence of ascaridoid nematodes in selected edible fish from the Persian Gulf and description of Hysterothylacium larval type XV and Hysterothylacium persicum n. sp. (Nematoda: Raphidascarididae).

Despite several reports on the presence of the potentially zoonotic nematodes among edible fishes in the Persian Gulf, there is still no study on the specific identification of these parasites or their genetic characterisation. In the present study, a total of 600 fish belonging to five popular species of fish in the region, including Otolithes ruber, Psettodes erumei, Saurida tumbil, Scomberomorus commerson and Sphyraena jello were examined for infection with nematode parasites. Detailed microscopy of nematodes found in the present study followed by characterisation of the first and second internal transcribed spacers (ITS-1 and ITS-2, respectively) showed that they belong to five distinct taxa that could be potentially zoonotic. Anisakis type I was found in four species of fish, had identical ITS sequences as Anisakis typica previously reported in Australian waters and was different from those reported in the Nearctic. Hysterothylacium type VI in the present study was morphologically similar to those previously described from Australasian waters and ITS sequences were identical among Australian specimens and those found in the present study. Another Hysterothylacium larval type was also found in the present study which had identical ITS sequences and similar morphology to those previously reported and identified as H. amoyense in China Sea. Since no ITS sequence data from a well identified adult H. amoyense with an identifiable museum voucher number is yet available and due to some other issues discussed in the article we suggest assignment of this larval type from the China Sea and the Persian Gulf to H. amoyense is doubtful until future studies on a well identified male specimen of H. amoyense or other species reveals the specific identity of this larval type. We propose to refer to this larval type as Hysterothylacium larval type XV. In the present study we also describe a new species, Hysterothylacium persicum and discuss how to differentiate it from closely related species. We also found some adult females with distinct morphology and ITS sequence but due to lack of male specimens they have been referred as Hysterothylacium sp. in this paper. They had the same ITS sequence data as Hysterothylacium larval type VI. This study shows the presence of a relatively broad diversity of potentially zoonotic nematodes in edible fish of the Persian Gulf. Therefore educational campaigns for public and local health practitioners are suggested to protect consumers from becoming infected with these parasites.