ichthyopathology

Ichthyopathology is the branch of veterinary pathology that studies diseases of fish, including wild populations and those kept in aquaculture, ornamentals, and laboratory settings. It encompasses the causes (aetiology), development (pathogenesis), diagnosis, treatment, and prevention of disease, as well as host–pathogen interactions and the influence of environmental factors on fish health. The field addresses infectious diseases caused by bacteria, viruses, fungi, and parasites, as well as noninfectious conditions such as toxic, nutritional, metabolic, genetic, and developmental disorders, and diseases related to water quality and husbandry.

Common etiologies include bacteria (e.g., Aeromonas, Vibrio species), viruses (e.g., infectious hematopoietic necrosis virus, koi herpesvirus, spring viremia of carp), parasites (e.g., Ichthyophthirius multifiliis, monogeneans), and fungi (Saprolegnia). Diagnostic workups rely on clinical signs and necropsy findings, supported by histopathology, microbiology, cytology, serology, culture, and molecular methods such as PCR and sequencing. Surveillance and quarantine are important components of prevention.

Management and treatment emphasize biosecurity, water-quality control, proper nutrition, and stress reduction. When appropriate and legally permitted, antimicrobial, antiparasitic, or antifungal therapies are used under veterinary guidance; vaccination and other preventive measures are available for selected pathogens and species.

Ichthyopathology informs aquaculture health programs, wild-fisheries management, and the ornamental fish trade, and it intersects with ichthyology, fish physiology, and veterinary medicine. It relies on laboratory diagnostics, field investigations, and ongoing research to mitigate disease impacts and promote fish welfare.