Potential Reservoirs and Risk Factors for VHSV IVb in an Enzootic System: Budd Lake, Michigan

Abstract

Viral hemorrhagic septicemia virus genotype IVb (VHSV IVb) has caused major, sporadic fish die-offs in the Laurentian Great Lakes region of North America since 2005. Presently, factors affecting VHSV IVb persistence in enzootic systems are not well understood. Even with annual surveillance, the virus can go undetected for several years after an outbreak before again re-emerging, which suggests that the virus is maintained in the system either below detectable levels or in untested reservoirs. The aim of this study was to identify potential reservoirs of VHSV IVb in Budd Lake, Michigan; VHSV IVb was first detected in Budd Lake in 2007 but remained undetected until 2011. Additionally, we explored the susceptibility of naive fish introduced into a water body enzootic for VHSV IVb by stocking age-0 Largemouth Bass Micropterus salmoides at varying densities into enclosures in the lake. The virus was not detected among samples of the fishes Notropis spp. and Lepomis spp., cylindrical papershell mussels Anodontoides ferussacianus, leeches (subclass Hirudinea), sediment, or water. However, the virus was successfully isolated from amphipods (family Hyalellidae) and Largemouth Bass held in the enclosures. Our finding of VHSV IVb in Hyalellidae amphipods in combination with other research that has detected the virus in Diporeia spp., a large benthic amphipod important as a food resource to Great Lake fishes, suggests that benthic macroinvertebrates are a reservoir for VHSV IVb in infected systems. If there are environmental reservoirs for VHSV IVb in infected systems, they are likely unevenly distributed. Findings of this study add to our understanding of the seemingly complex ecology of this deadly and economically detrimental virus. Received February 22, 2016; accepted October 16, 2016.

Evolutionary trajectory of fishPiscine novirhabdovirus(=Viral Hemorrhagic Septicemia Virus) across its Laurentian Great Lakes history: Spatial and temporal diversification

“…Throckmorton et al. (2017) likewise discovered no VHSV in cylindrical papershell mussels ( Anodontoides ferussacianus ) from Budd Lake, despite positive largemouth bass and Hyalellidae amphipods from that location. Researchers in Denmark tested for a VHSV‐II invertebrate reservoir in isopods, krill, and squid, but none were positive (Skall, Olesen, & Mellergaard, 2005).…”

“…It has been postulated that some invertebrates may harbor VHSV‐IVb, serving as possible reservoirs, including Hyalellidae amphipods (Throckmorton et al., 2017), Pontoporeiidae amphipods (e.g., Diporeia spp. ; Faisal & Winters, 2011), and an individual leech ( Myzobdella lugubris ) (Faisal & Schulz, 2009).…”

Comparative effects of Novirhabdovirus genes on modulating constitutive transcription and innate antiviral responses, in different teleost host cell types

“…We focused on Novirhabdoviruses of economic or ecological importance in North America: VHSV-IVb and IHNV-M genotypes. VHSV-IVb is of significant ecological concern in the Laurentian Great Lakes region where sporadic outbreaks have occurred over the past 17 years [31,65,66], thus there is tangible risk to all farmed fish in the region. But to date, VHSV-IVb has shown limited pathogenicity toward rainbow and brown trout [24,54], this could enable the disease to go undetected in a production setting.…”

Isolation and identification of a viral haemorrhagic septicaemia virus (VHSV) isolate from wild largemouth bass Micropterus salmoides in China

“…Until now, several different virus strains have been isolated from cultured and wild largemouth bass, such as ranavirus, VHSV, megalocytivirus and siniperca chuatsi rhabdovirus (Groocock, Grimmett, Getchell, Wooster, & Bowser, ; Ma et al, ; Mao, Wang, Chinchar, & Chinchar, ; Throckmorton et al, ). Among them, VHSV, a highly contagious fish pathogen, has caused serious economic damage to the production and quality of a wide range of fish species including but not limited to largemouth bass all over the world (Kim et al, ; Pereiro, Figueras, & Novoa, ; Throckmorton et al, ). Many wild fish have been reported to be carriers of VHSV, including olive flounder, silver pomfret and so on (Kim et al, ; Lee, Yun, Kim, Jung, & Oh, ), these VHSV‐positive fish had a major role in VHSV transmission.…”

“…Here, the phylogenetic analysis based on the whole‐genome sequences and G gene sequences revealed that the VHSVLB2018 isolate belonged to genotype IVa, which is similar to the VHSV isolates from other fishes in Asia (Kim et al, ). Differently, a VHSV isolate of genotype IVb was detected from largemouth bass in the great lakes region in the United States and Canada (Kim & Faisal, ; Throckmorton et al, ). Since the first VHSV strain was isolated from farmed Japanese flounder in Japan (Takano, Nishizawa, Arimoto, & Muroga, ), many different strains of VHSV have been reported in a wide range of fish species in Asia.…”