Carp edema virus infection associated gill pathobiome: A case report

Area of Science:

• Ichthyopathology
• Aquatic microbiology
• Fish immunology

Background:

• Understanding fish disease etiology is crucial for aquaculture and wild fish health.
• Carp edema virus (CEV) causes significant mortality in common carp (Cyprinus carpio), leading to carp edema virus disease (CEVD).
• Gill health is vital for fish respiration and homeostasis.

Observation:

• CEV infection was identified in both carp and their ectoparasite Argulus foliaceus from a high-mortality pond.
• Gill examination revealed colonization by free-living eukaryotes (amoebae, ciliates) and Ichthyobodo spp.
• Bacterial communities, including Flavobacterium species, were detected within gill tissues and associated amoebae.

Findings:

• Eukaryotic organisms on carp gills can contribute to gill structure and function alterations.
• Specific Flavobacterium species (F. swingsii, F. psychrophilum) were prevalent within amoebae, correlating with lesion severity.
• The study highlights the complex interplay between bacterial assemblages and eukaryotic co-pathogens in CEVD.

Implications:

• Eukaryotic organisms within the gill pathobiome may exacerbate irreversible gill lesions in CEVD.
• Further research is needed to elucidate the factors triggering pathology and influencing disease severity in CEV-positive carp.
• This emphasizes the need for a holistic approach to understanding fish diseases, considering multi-organismal interactions.