Could mycotoxigenic Fusarium sp. play a role in ulcerative dermal necrosis (UDN) of brown trout (Salmo trutta morpha trutta)?

Agnieszka Pękala-Safińska,Anna Kycko,Piotr Jedziniak,Łukasz Panasiuk,Leszek Jerzak,Ewa Paździor,Mateusz Ciepliński,Mariusz Kasprzak

doi:10.1007/s12550-020-00395-8

Agnieszka Pękala-Safińska, Anna Kycko + Show 6 more

Open Access

https://doi.org/10.1007/s12550-020-00395-8

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Abstract

Fusarium infections have been reported in aquatic animals, but are still poorly investigated in wild salmonids. The aim of the study was to determine the impact of the fungi and their toxins on the health status of brown trout (Salmo trutta morpha trutta) migrating from the Baltic Sea to the freshwater. Individuals from the wild brown trout population exhibiting ulcerative skin lesions were collected from the Słupia River in Poland and subjected to microbiological, histopathological, and hematological examinations, as well as toxicological analysis for a presence of mycotoxins. The results of microflora isolation from the brown trout skin samples revealed the presence of conditionally pathogenic bacteria and fungi classified by molecular techniques as Fusarium spp. Toxicological analysis allowed for detection of zearalenone (ZEN) in the liver, kidney, and gastrointestinal tract of the fish. In several cases, there was α-zearalenone (α-ZEL) identified at trace levels in the liver, as well as sterigmatocystin and enniatin B at low levels in the kidney and the liver. Histopathological examination revealed the presence of fungal hyphae disrupting the epidermis and penetrating into the necrotic dermis and hypodermis. The decreased values of the blood parameters, i.e., hemoglobin concentration (HGB), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and white blood cell count (WBC), were indicative of osmoregulation failure being a consequence of the skin damage. The results of the study provide new information regarding Fusarium sp. infection in brown trout and serve as the basis for further research on the potential impact of the fungi and their mycotoxins on the Baltic salmonid population, including their role in ulcerative dermal necrosis.

Highlights

Fusarium is a genus of fungi which belong to the phylum Ascomycota, class Sordariomycetes (Buller 2014)
Bacteriological studies of the skin lesion samples supported by molecular analysis revealed the following dominant species of bacteria: Acinetobacter spp., motile and mesophilic Aeromonas strains like Aeromonas hydrophila and Aeromonas sobria, Chryseobacterium spp., Pseudomonas fluorescens, Serratia liquefaciens, and Shewanella spp
Prominent health disorders and mass mortality of brown trout spawners were noticed in many Polish rivers during the return of fish from the Baltic Sea to the river for spawning

Summary

Introduction

Fusarium is a genus of fungi which belong to the phylum Ascomycota, class Sordariomycetes (Buller 2014). They are known as ubiquitous organisms widely distributed throughout the world, both in temperate and in tropical regions. The compounds above caused systemic disorders manifesting themselves by hepatotoxic, nephrotoxic, cardiotoxic, dermatotoxic, and neurotoxic effects. They have been found to affect the hormonal balance and reduce immunity (Chełkowski 1985; Pietsch et al 2015a). There are still gaps of knowledge concerning the impact of Fusarium species and their toxins on the health status of fish, especially Salmonidae

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