Saprolegnia parasitica Isolated from Rainbow Trout in Korea: Characterization, Anti-Saprolegnia Activity and Host Pathogen Interaction in Zebrafish Disease Model

Saprolegniasis is one of the most devastating oomycete diseases in freshwater fish which is caused by species in the genus Saprolegnia including Saprolegnia parasitica. In this study, we isolated the strain of S. parasitica from diseased rainbow trout in Korea. Morphological and molecular based identification confirmed that isolated oomycete belongs to the member of S. parasitica, supported by its typical features including cotton-like mycelium, zoospores and phylogenetic analysis with internal transcribed spacer region. Pathogenicity of isolated S. parasitica was developed in embryo, juvenile, and adult zebrafish as a disease model. Host-pathogen interaction in adult zebrafish was investigated at transcriptional level. Upon infection with S. parasitica, pathogen/antigen recognition and signaling (TLR2, TLR4b, TLR5b, NOD1, and major histocompatibility complex class I), pro/anti-inflammatory cytokines (interleukin [IL]-1β, tumor necrosis factor α, IL-6, IL-8, interferon γ, IL-12, and IL-10), matrix metalloproteinase (MMP9 and MMP13), cell surface molecules (CD8⁺ and CD4⁺) and antioxidant enzymes (superoxide dismutase, catalase) related genes were differentially modulated at 3- and 12-hr post infection. As an anti-Saprolegnia agent, plant based lawsone was applied to investigate on the susceptibility of S. parasitica showing the minimum inhibitory concentration and percentage inhibition of radial growth as 200 μg/mL and 31.8%, respectively. Moreover, natural lawsone changed the membrane permeability of S. parasitica mycelium and caused irreversible damage and disintegration to the cellular membranes of S. parasitica. Transcriptional responses of the genes of S. parasitica mycelium exposed to lawsone were altered, indicating that lawsone could be a potential anti-S. parasitica agent for controlling S. parasitica infection.

Studies on the identification and control of pathogen Saprolegnia in selected Indian major carp fingerlings at mid hill altitude.

The Indian major carp cultured in ponds in the North Eastern hilly states of India frequently suffer from fungal disease during winter months resulting in mass mortality. This study examined the pathogenic fungi isolated from farmed raised Indian major carp fingerlings and identified as Saprolegnia. For treatment, the diseased fish were exposed to 4g salt per litre of water for 2 min followed by dip treatment with 5ppm KMnO4 for 10 min, thrice every week for a period of 6 weeks. The treatment resulted in recovery from the disease after 6 weeks from the beginning of treatment. Soon after recovery, the pond management practices such as removal of pond bottom soil, application of lime and replenishment with freshwater were followed in the infected ponds. Our study concluded that rapid decrease in pond water temperature from 22 to 8°C that remains low for months together coupled with increased water pH (9) and decreas dissolved oxygen (4ppm) causes saprolegniasis to the fingerlings of Indian major carps.

First record of Saprolegnia sp. in an amphibian population in Colombia / Primer registro de Saprolegnia sp. en una población de anfibios en Colombia / Primeiro registro de Saprolegnia sp. numa população de anfíbios na Colômbia

Primer registro de Saprolegnia sp. en una población de anfibios en Colombia. Objetivo. La mayoría de investigaciones en relación al declive de anfibios se han enfocado en la detección del hongo patógeno Batrachochytrium dendrobatidis. Este es el principal patógeno detectado en el mundo. Sin embargo, otras investigaciones han demostrado la presencia de Saprolegnia ferax como un vector mortal en anfibios de Norteamérica. Este trabajo establece una posible transmisión entre especies causada por la presencia de la trucha arcoíris, sugiriendo que el declive de anfibios no solo se atribuye a la presencia de un solo patógeno, sino que puede ser causado por otros patógenos y factores. Materiales y métodos. El estudio revela la presencia de Saprolegnia sp. en la rana de los Andes Atelopus mittermeieri mediante la técnica de impronta con tinción de azul de lactofenol, que permitió la observación de las estructuras típicas de este hongo. Resultados. La importancia de este descubrimiento es la presencia de dos hongos patógenos, B. dendrobatidis y Saprolegnia, afectando simultáneamente una población de anfibios. Este hallazgo enfoca la atención en la eventual presencia de otros microorganismos que podrían estar involucrados individualmente o colectivamente en el declive de especies de anfibios. Conclusiones. Este registro sugiere una posible transmisión entre la trucha arcoiris (Oncorhynchus mykiss), una especie introducida en las montañas de Colombia, que comparte los mismos habitats con diferentes especies de anfibios en el Santuario de Flora y Fauna de Guanentá en el alto río Fonce en la parte media de la Cordillera Oriental de Colombia...

Objective: Most research related to the decline of amphibians has been focused on the detection of the pathogenic fungus Batrachochytrium dendrobatidis. This fungus is the main pathogen detected around the world. However, research has shown the presence of another fungus, Saprolegnia ferax, as a cause of mortality in amphibians in North America. Our study suggests a possible interspecific transmission caused by the presence of rainbow trout; thus, amphibian declines may not be attributable only to the presence of a single pathogen, but to other organisms and factors. Materials and methods. Our study revealed the presence of Saprolegnia sp. in the Andean frog Atelopus mittermeieri using the imprinting technique with lactophenol blue staining, which allowed the typical structures of this fungus to be observed. Results. The importance of this discovery is the presence of two pathogenic fungi, B. dendrobatidis and Saprolegnia, which affecting simultaneously a population of amphibians. This finding brings attention to the eventual presence of other microorganisms that might be involved individually or collectively in the decline of amphibian species. Conclusions. This record suggests a possible transmission between rainbow trout (Oncorhynchus mykiss), an introduced species in the highlands of Colombia, which shares the same habitats with different species of amphibians in the Sanctuary of Flora and Fauna Guanentá in the upper river Fonce in the mid Cordillera Oriental of Colombia...

Primeiro registro de Saprolegnia sp. numa população de anfíbios na Colômbia. Objetivo. A maioria das pesquisas sobre o declínio dos anfíbios tem-se centrado na detecção do fungo patogênico Batrachochytrium dendrobatidis. Este é o principal patógeno encontrado no mundo. No entanto, outros estudos têm demonstrado a presença de Saprolegnia ferax, como vetor mortal de anfíbios de América do Norte. Esta pesquisa estabelece uma possível transmissão entre espécies causada pela presença de truta arco-íris, afirmando que o declínio de anfíbios não só é atribuído à presença de um único patógeno, pudendo ser causado por outros patógenos e fatores. Materiais e métodos. A pesquisa indica a presença de Saprolegnia sp. em rãs dos Andes, Atelopus mittermeieri, pela técnica de impressão com lactofenol-azul-de-algodão, onde observou-se as estruturas típicas deste fungo. Resultados. A importância desta descoberta é a presença de dois fungos (B. dendrobatidis e Saprolegnia) que simultaneamente afetam uma população de anfíbios, concentrando a atenção na presença de outros microorganismos que podem estar envolvidos individualmente ou coletivamente no declínio das espécies de anfíbios. Conclusões. A truta arco-íris (Oncorhynchus mykiss), uma espécie introduzida nas montanhas da Colômbia, que compartilha o mesmo nicho ecológico com Atelopus mittermeieri, no Santuário de Flora e Fauna de Guanentá no Alto Rio Fonce no centro da Cordilheira Oriental da Colômbia, tem sido sugerida por esta pesquisa como o agente transmissor dos fungos as diferentes espécies de anfíbios...