Abstract

The Epizootic Ulcerative Syndrome (EUS) is a devastating fungal disease in freshwater fish, significantly impacting aquaculture industries and biodiversity. This study investigates the pathological and molecular characteristics of EUS caused by Aspergillus fumigatus. Freshwater fish of Channa striatus specimens exhibiting clinical EUS signs were examined through histopathological, microbiological, and molecular techniques. The pathogen was isolated, identified, and its virulence factors characterized. The findings highlight the pathological lesions, immune responses, and molecular markers associated with A. fumigatus infections. Understanding these mechanisms provides valuable insights for disease management and prevention strategies in aquaculture systems.

Keywords:Epizootic Ulcerative Syndrome; Aspergillus fumigatus; Channa striatus; Molecular characterization; Pathology

Introduction

The Epizootic Ulcerative Syndrome (EUS) is a fungal disease affecting a wide range of freshwater and estuarine fish species globally. Characterized by necrotic ulcers and high mortality rates, EUS has posed significant challenges to the aquaculture industry and aquatic ecosystems. Subramanian P, et al. (2023) [1]. Fungi such as Aspergillus fumigatus, have emerged as complicated factors that exacerbate the disease pathology. Aspergillus fumigatus, a ubiquitous fungus, is known for its adaptability and ability to infect immunocompromised hosts. Its role in fish diseases, particularly in EUS, remains underexplored. Chandra S, et al. (2023) [2]. This study aims to bridge this knowledge gap by characterizing the pathological and molecular features of EUS caused by A. fumigatus. The research highlights the significance of early detection and pathogen-specific management approaches for sustainable aquaculture. Reza AS, and Rahman MM (2023) [3].

Materials and Methods

Sample collection: Fish specimens with clinical signs of EUS (ulcers, hemorrhagic lesions) were collected from freshwater bodies in affected regions.

Histopathological analysis: Tissue samples (skin, gills, liver) were fixed in 10% formalin, processed for paraffin embedding, and stained with AZAN for microscopic examination.

Fungal isolation and identification:

•Lesions were swabbed and cultured on Sabouraud dextrose agar.
•Fungal colonies were identified morphologically and confirmed using molecular techniques.

Molecular characterization:

•DNA was extracted from isolated fungi and amplified using species-specific primers targeting the ITS region.
•Sequencing and phylogenetic analyses were performed to confirm fungal identity.

Pathogenicity assays:

Healthy fish were exposed to fungal spores to confirm pathogenicity and study disease progression under controlled conditions.

Data analysis: Statistical analyses were conducted to compare pathological features and immune responses between infected and control groups.

Results and Discussion

The histopathological analysis revealed severe necrosis, granuloma formation, and vascular damage in tissues of infected fish. Aspergillus fumigatus was successfully isolated and confirmed via molecular characterization, with ITS sequencing demonstrating >99% similarity to reference strains. Saylor RK, et al. (2023) [4]. Pathogenicity assays confirmed its role in exacerbating EUS pathology. Hossain MA, et al. (2022) [5]. Immune responses, including elevated pro-inflammatory cytokines, were noted in infected fish. These findings suggest that A. fumigatus acts as a secondary pathogen that intensifies the disease process Roberts RJ (2022). The study underscores the complexity of EUS as a polymicrobial disease and highlights the need for integrated management strategies targeting both primary and secondary pathogens. Hossain Z, et al. (2023) [5].

Conclusion

This study provides comprehensive pathological and molecular insights into EUS in freshwater fish caused by Aspergillus fumigatus. The findings emphasize the role of secondary fungal infections in aggravating disease severity and call for pathogen-specific interventions. Future research should focus on developing rapid diagnostic tools and exploring antifungal treatments to mitigate EUS outbreaks effectively.

References

1. Subramanian P, et al. (2023) Pathogenicity of Aspergillus fumigatus in aquatic organisms. Journal of Mycology 38(2): 233-246.
2. Chandra S, et al. (2023) Integrated management of fish fungal infections. Aquaculture International 31(5): 823-836.
3. Reza AS, Rahman MM (2023) Secondary fungal infections in aquaculture systems. Aquaculture Research 54(2): 120-135.
4. Saylor RK, et al. (2023) Molecular insights into fungal infections in aquaculture. Journal of Fish Diseases 46(3): 210-225.
5. Hossain Z, et al. (2023) Pathogen interaction in polymicrobial fish diseases. Aquatic Microbial Ecology 87(1): 25-38.
6. Moriarty DJW (2023) Advances in fungal pathogen identification in aquaculture. Fungal Biology Reviews 62(3): 145-160.