Distribution of an Invasive Aquatic Pathogen (Viral Hemorrhagic Septicemia Virus) in the Great Lakes and Its Relationship to Shipping

Viral hemorrhagic septicemia virus (VHSV) is a rhabdovirus found in fish from oceans of the northern hemisphere and freshwaters of Europe. It has caused extensive losses of cultured and wild fish and has become established in the North American Great Lakes. Large die-offs of wild fish in the Great Lakes due to VHSV have alarmed the public and provoked government attention on the introduction and spread of aquatic animal pathogens in freshwaters. We investigated the relations between VHSV dispersion and shipping and boating activity in the Great Lakes by sampling fish and water at sites that were commercial shipping harbors, recreational boating centers, and open shorelines. Fish and water samples were individually analyzed for VHSV using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and cell culture assays. Of 1,221 fish of 17 species, 55 were VHSV positive with highly varied qRT-PCR titers (1 to 5,950,000 N gene copies). The detections of VHSV in fish and water samples were closely associated and the virus was detected in 21 of 30 sites sampled. The occurrence of VHSV was not related to type of site or shipping related invasion hotspots. Our results indicate that VHSV is widely dispersed in the Great Lakes and is both an enzootic and epizootic pathogen. We demonstrate that pathogen distribution information could be developed quickly and is clearly needed for aquatic ecosystem conservation, management of affected populations, and informed regulation of the worldwide trade of aquatic organisms

Fish analyzed for VHSV and number of fish determined to be positive with data on fish sizes and known vulnerability to VHSV.

<p>1. VHSV susceptibility is reported by the U.S. Department of Agriculture, Animal and Plant Health Inspection Service <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010156#pone.0010156-Center1" target="_blank">[12]</a> although other species can be infected.</p

Distribution of VHSV positive fish in the Great Lakes from 2003 through 2008 as reported by the U.S. Department of Agriculture Animal and Plant Health Inspection Service [12] and the distribution of documented invasion hotspots [18], [27].

<p>Distribution of VHSV positive fish in the Great Lakes from 2003 through 2008 as reported by the U.S. Department of Agriculture Animal and Plant Health Inspection Service <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010156#pone.0010156-Center1" target="_blank">[12]</a> and the distribution of documented invasion hotspots <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010156#pone.0010156-Grigorovich1" target="_blank">[18]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010156#pone.0010156-Cangelosi1" target="_blank">[27]</a>.</p

Detection of VHSV in fish and water and the presence of VHSV positive fish at sampling sites in and outside of invasion hotspots shown in Figure 1.

<p>Detection of VHSV in fish and water and the presence of VHSV positive fish at sampling sites in and outside of invasion hotspots shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0010156#pone-0010156-g001" target="_blank">Figure 1</a>.</p

VHSV detection in fish and water using qRT-PCR and cell culture assays shown by site, type of site, and number of fish tested.

<p>VHSV detection in fish and water using qRT-PCR and cell culture assays shown by site, type of site, and number of fish tested.</p

Distribution of VHSV positive fish and water at sites classified as commercial shipping harbors, recreational boating centers, and open shoreline.

<p>Distribution of VHSV positive fish and water at sites classified as commercial shipping harbors, recreational boating centers, and open shoreline.</p