Molecular Epidemiology of Outbreaks of Spring Viremia of Carp Virus in North America, Europe and Asia

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Title: Molecular Epidemiology of Outbreaks of Spring Viremia of Carp Virus in North America, Europe and Asia
Author: Miller, Otis Jr.
Advisors: J. F. Levine, Committee Member
G. A. Lewbart, Committee Member
W. A. Gebreyes, Committee Member
F. J. Fuller, Committee Chair
Abstract: Spring Viremia of Carp Virus (SVCV) or Rhabdovirus carpio is the causative agent of the fish disease, Spring Viremia of Carp (SVC). Genetic relationships between 35 spring viremia of carp virus (SVCV) genogroup Ia isolates were determined based on the nucleotide sequence of the phosphoprotein (P) gene and glycoprotein (G) genes. Phylogenetic analysis based on P-gene sequences revealed two distinct subgroups within the SVCV genogroup Ia, designated SVCV Iai and Iaii, and suggests at least two independent introductions of the virus in the USA in 2002. Combined P - and G - sequence data support the emergence of SVCV in Illinois, USA and Lake Ontario, Canada, from the initial outbreak in Wisconsin, USA, and demonstrate a close genetic link to viruses isolated during routine import checks on fish brought into the UK from Asia. The data also showed a genetic link between SVCV isolations made in Missouri and Washington, USA, in 2004 and the earlier isolation made in North Carolina, USA, in 2002. However, based on the close relationship to a 2004 UK isolate, the data suggests that the Washington isolate represents a third introduction into the US from a common source, rather than a re-emergence from the 2002 isolate. There was strong phylogenetic support for an Asian origin for 9 of 16 UK viruses isolated either from imported fish, or shown to have been in direct contact with fish imported from Asia. In one case, there was 100% nucleotide identity in the G-gene with a virus isolated in the Peoples Republic of China. The remaining portion of this dissertation deals with biosecurity on ornamental fish farms. A good biosecurity program results in control of disease transmission by eliminating pathogen introduction onto farm(s) and dissemination between farms or between ponds on any farm. Each method of possible pathogen movement to new susceptible animals is addressed by a biosecurity plan and prevention is implemented by education and appropriate actions of employees. A biosecurity plan seeks to control: 1. people carrying pathogens on person including visitors and employees, 2. inspection and quarantine of incoming fish, 3. contaminated inanimate objects like vehicles, nets, and other equipment, 4. wild animals that may act as vectors for the pathogen, and 5. water source. Daily operations of a farm must focus on these controls to prevent disease incidence, or if disease has already occurred, its spread. This paper will introduce, through phylogenetic analyses, countries of interest for disease risk to SVCV and introduce a risk assessment tool that can identify biosecurity measures for establishing a biosecurity plan suitable for the control and prevention of one of the industries' disruptive and economical devastating infectious disease, spring viremia of carp.
Date: 2007-11-01
Degree: PhD
Discipline: Comparative Biomedical Sciences

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