Aquatics Viral Infections Study Guide

Overview and Clinical Importance

Viral diseases of fish represent a significant category of aquatic animal diseases on the NAVLE examination. Two of the most economically and clinically important viral infections affecting cyprinid fish species are Spring Viremia of Carp (SVC) and Koi Herpesvirus Disease (KHVD). Both diseases are notifiable to the World Organisation for Animal Health (WOAH, formerly OIE) and can cause devastating mortality in affected populations. Understanding the epidemiology, clinical presentation, diagnostic approaches, and regulatory implications of these diseases is essential for veterinary practice.

Section 1: Spring Viremia of Carp (SVC)

Etiology and Virology

Spring Viremia of Carp (SVC) is caused by Carp sprivivirus (Rhabdovirus carpio), a bullet-shaped, enveloped, single-stranded negative-sense RNA virus belonging to the family Rhabdoviridae, genus Sprivivirus (formerly Vesiculovirus). The viral genome contains five genes encoding nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G), and polymerase (L) in the order 3'-NPMGL-5'.

SVCV Characteristics

Epidemiology

Geographic Distribution

SVC was initially diagnosed in Yugoslavia in 1971 and has since been identified throughout Europe, Russia, the Middle East, China, Brazil, and North America. In the United States, SVC was first confirmed in 2002 in farmed koi from North Carolina and wild carp in Wisconsin. Additional US cases occurred in Washington and Missouri (2004) and Minnesota (2007, 2011). SVCV is NOT considered widespread in the US and is classified as a foreign animal disease for regulatory purposes.